CA1297638C

CA1297638C - Absorbent article

Info

Publication number: CA1297638C
Application number: CA000536460A
Authority: CA
Inventors: Daisuke Shiba; Iwao Miyashita; Akira Sakurai
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 1986-05-07
Filing date: 1987-05-06
Publication date: 1992-03-24
Anticipated expiration: 2009-03-24
Also published as: ES2025160B3; EP0245074A3; SG124992G; JPH0687874B2; US4804378A; EP0245074B1; MY100847A; DE3773254D1; EP0245074A2; PH22590A; HK32693A; JPS62261363A

Abstract

ABSTRACT OF THE DISCLOSURE
An absorbing article comprises a non-woven fabric layer comprising a surface layer to be in contact with skins containing from 60 to 100% by weight of first fibers having a hydrophilic surface and a hydrophobic inside and from 40 to 0% by weight of second fibers which are hydrophilic at least at their surface, and a rearface layer containing from 0 to 50% by weight of said first fibers and from 100 to 50% by weight of said second fibers, in which the surface hydrophilicity of said second fibers, after being wetted, is greater than said first fibers.

Description

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The invention relates to an absorbent article such as a sanitary napkin and a disposable diaper having an excellent absorption property. In particular, the invention relates to an improvement of a non-woven fabric used in the absorbent article.
The invention applies to an absorbent article comprising a non-woven fabric layer and an absorbent material such as fluff pulp (also called as cotton-like pulp), an absorbing paper and an absorbent polymer. It may further comprise a leak-proof layer on the back side. The disposable diaper is also called a paper diaper.
Various performances are required for the non-woven fabrics constituting the top face of such absorbing articles and most important performances among them are restriction of the flow or a discharged liquld ~i.e., urine or menstrual blood), which may lead to leakage, reduction of the return of the liquid maintained in the absorbing layer to skins, comfortable feeling upon contact with skins, etc.
; In conventional absorbing articles, for restricting the liquid flow, regenerated hydrophilic fiber such aæ rayon have been used as a material for the non-woven fabric. However, the regenerated hydrophilic fiber~ are formed solely or together with hydrophobic fibers uniformly into non-woven fabrics in the conventional absorblng articles. Since the surface of the hydrophobic fibers is water repellent, the regenerated hydrophilic fibers have to be used in an extremely high amount for imparting sufficient hydrophilic property to the surface of the non-woven fabrics where the regenerated hydrophilic fibers are mixed with hydrophobic fibers. The use of the regenerated hydrophilic fiber "C

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increases a water absorbing rate at the surface of the non-woven fabrics and decreases the liquid flow at the surface. However, since the regenerated hydrophilic fibers themselves absorb water to inside thereof, such fibers have a strong water retaining capacity and decrease its volume upon wetting. Thus, when the surface of the non-woven fabrics gets wet, the surface in contact with a s~in becomes highly sticky and the liquid tends to return from the absorbing layer to the skin. These result in problems such as worsened or uncomfortable feeling and skin eruptions.
Recently, use of dry non-woven fabrics mainly composed of synthetic fibers has become remarkably popular as a surface material of the absorbing articles and the foregoing problems of the stickiness and remarkable liquid return inherent to the non-woven fabrics malnly composed of regenerated hydrophilic fibers have gradually been improved. However, since conventional dry non-woven fabrics made of hydrophobic flbers have a water repellent surface, they cause remarkable liquid flow and trend of liquid leakage. In addition, an attempt has been made to treat such hydrophobic fibers with a surface active agent in order to render the surface of the non-woven fabrics hydrophilic and to restrict the liquid flow at the surface. However, where the hydrophobic fibers are merely treated with a surface active agent, their surface hydrophilicity does not last long once they get wet. So, after menstrual blood or urine has once permeated, the ; hydrophilicity at that portion is greatly reduced. If menstrual blood or urine is dlscharged to the same portion of the non-woven fabrics next time, the liquid is also liable to flow, thereby making it difficult to maintain the initial performance during the ' ' :

use of the absorbing article.
Further, as shown in Japanese Patent Laid-open No. 60-19~3151, it has also been attempted to treat the hydrophobic fibers having absorbed sweat or water with a high speed water stream to form non-woven fabrics in order to impart durability to the hydrophilic property of the non-woven fabrics. However, no consideration was made to the constitution of the fibers. Since an upper layer is mainly composed of hydrophobic fibers, liquid tends to readily flow and, further, sweat-water-absorbing agents at the surface of the fibers are washed out upon high speed water treatment. Thus, the hydrophilic property of the non-woven fabrics upon practical use is greatly reduced and a sufficient water absorblng rate was not obtained.
Although improvements have been reported in commercially available articles, such as application of various water-absorbing high molecular materials as an absorbing material, there have not yet been found absorbing articles capable of satisfying both an absorbing rate (surface liquid flow) and a liquid returning performance.
The present inventors have made an earnest study trying to improve non-woven fabrics used so far as a surface material of the absorbing articles, that is, for finding non-woven fabrics ca~able of satisfying both of the absorbing rate and the liquid return and, as a result, have accomplished this invention.
Thus, the present invention provides an absorbent article comprising~
a non-woven fabric layer which is to be in contact with skin when the absorbent artlcle ls in use; and C

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an absorbent material behind the non-woven fabric layer, wherein the non-woven fabric layer comprises:
(1) a surface layer comprising 60 to 100 percent by weight of first fibers having a hydrophilic surface portion and a hydrophobic inside portion and from 40 to zero percent by weight of second fibers which are hydrophilic at least at a surface thereof, and (2) a back layer containing at least one layer comprising from zero to 50 percent by weight of the said first fibers and from 100 to 50 percent by weight of the said second fibers, the said second fibers being more hydrophilic at a surface than the said first fibers after getting wet.
It is preferred that the surface layer solely consists of the first flbers and the back layer solely consists of the second fibers. It is preferable that the first flbers have been formed by making the surface of hydrophobic fibers hydrophilic and the second fibers are hydrophilic fibers ~i.e., hydrophilic both at the surface and inside) or have been formed by making the surface of hydrophobic fibers hydrophllic.
It is preferred that the first fibers of the surface layer, when first wetted and then dried, have a surface hydrophiliclty of not more than 0.5 ml and the second fibers of the back layer, when first wetted and then dried, have a surface hydrophilicity of 1 to 2 ml.
~; ~ The present invention is described in further detail below. For better understanding of the invention, reference may be made to the drawing in whichs Fig. 1 schematically shows a device used in the Examples :'C

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for measuring the hydrophilicity of fibers, and Fig. 2 is a cross sectional view of a typical absorbent article according to one preferred embodiment of the present invention.
Referring to Fig. 2, the absorbent article according to the present invention comprises a non-woven fabric layer 9 which is to be in contact with the skin when in use and an absorbent material 10. Very often, a leak-proof layer 11 is also provided.
The non-woven fabric layer 9 consists of a surface layer 7 and a back layer 8.
The first fibers referred to herein may be a mixture of two or more different hydrophobic fibers in which the surface hydrophilicity after wetting is low. The second fibers referred to herein may be a mixture of two or more different hydrophobic fibers in which the surface hydrophilicity after wetting is higher than that of the first fibers described above.
In order that the non-woven fabrics can rapidly pass liquid such as body fluids to the absorbing layer, it is necessary that the surface of the fibers constituting the non-woven fabrics is sufficiently hydrophilic at least in the situation where the absorbing article is constituted with the non-woven fabrics.
However, the liquid once absorbed in the absorbing layer is likely to return to the outside through the non-woven fabrics if the hydrophilicity at the surface of the fibers is excessively high.
Therefore, it is desirable that the hydrophilicity of at least the surface layer of the non-'~' 1~97638 woven fabrics which is to be in contact with the skins when in use is rather low for preventing the passage of water. In order to provide the surface layer of the non-woven fabrics with such a property, it is necessary that the proportion of the first fibers in the surface layer is at least 60% by weight and, preferably, 100~. That is, the fibers hydrophilic at the surface and hydrophobic inside and preferably having a low water retainability should be at least 60% by weight of the surface layer. In this context, the low water retainability should be understood to mean that the hydrophilicity after wetting is lower as compared with that before the wetting.
The hydrophilicity of the first fibers after wetting and drying (Hw) is preferably less than 0.5 ml, more preferably, C less than 0.3 ml according to t~n! test method for water absorption amount as described later in Examples. Namely, the hydrophilicity is defined by the amount of water (ml) absorbed by ~e fibers through a glass filter placed at ~h~ bottom thereof when the fibers packed at a density of 0.13 g/cm3 in an uprightly standing glass tube having an inner diameter of 14 mm are left under atmospheric hydraulic pressure at the bottom for one minute.
Then, it is necessary that the liquid absorbing rate at the surface of the non-woven fabrics is not reduced even if the surface hydrophilicity is lowered due to the passage of water. For this purpose, a rearface layer (i.e. back layer~
must be present comprising at least one layex of fibers whose hydrophilicity at least at the surface is not reduced so much 12~7~;3~

after wetting as the first fibers. The weight ratio in the back layer of the second fibers having a surface hydrophilicity after wetting higher than that of the first fibers is greater than that in the surface layer. In this case, for obtaining an effect that the liquid absorbing rate at the surface oE
the non-woven fabrics is not reduced even if the surface hydrophilicity is lowered due to the passage of water, it is necessary that the weight ratio of the second fibers constituting the back layer is at least 50% and it may be 100%
so long as the fibers constituting the surface layer lies within the range described above.
For maintaining the absorbing rate more effectively, it is desirable that the hydrophilicity of the second fibers after wetting (Hw) is more than 1 ml according to the test method for the water absorption amount mentioned above and more specifically described later in the Examples. For reducing the liquid return, it is better that the second fibers also have a hydrophilic surface and a hydrophobic inside and the water retainibility of the fibers per se is lower and, most desirably, all of the second fibers are made of such fibers. Further, it is more preferable that the hydrophilicity of the second fibers after wetting is less than 2 ml according to the test method for the water absorption amount mentioned above. For usual absorbent articles such as sanitary napkins, paper diapers and the like~ a single layer may be sufficient for the rearface layer but a multi-layered structure may be necessary for such applications that require a greater thickness.

~7638 The first fibers and the second fibers may be different from each other with respect to the surface layer and the rearface layer and it is desirable that the difference in the hydrophili-city between the first and second fibers is large because it better reduces the liquid return.
The first fibers and the second fibers as described above can be prepared by subjecting the surface o hydrophobic fibers to a hydrophilic treatment and further controlling the durability of the hydrophilic treatment to the water content.
The second fibers may be hydrophilic only at the surface or they may be hydrophilic inside as well. The latter includes rayon fibers.
The methods of applying the surface hydrophilic treatment to the hydrophobic fibers include, for example, a method of rendering the surface of hydrophobic synthetic fibers hydrophilic, using a surface active agent. The hydrophobic synthetic fibers are, for example, polyolefin fibers, for example, of polyethylene and polypropylene; polyester fibers;
polyamide fibers; and polyacrylonitrile fibers. The surface may be rendered hydrophilic by applying a surface chemical treatment such as chemically bonding those chemical materials having hydrophilic groups such as monomers having hydrophilic groups or polymers having hydrophilic groups, or a physical surface modification such as plasms fabrication and incorporation of chemical material having hydrophilic groups by kneading. For the chemical surface modification, those chemical materials having hydrophilic groups may be chemically :~,. . . .

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bonded with the fibex suxface, QX chemical materials having hydroph.ilic groups may be bonded and crosslinked to each other to cover the surface of the fibers. Further, it is also possible to improve the water absorbing property by making the shape of the hydrophobic fibers into a profile configuration, or applying a hydrophilic treatment to the surface of them.
Since the method of surface hydrophilic treatment can .. , ~, .. .

129~

control the durability to water by adequately selecting process conditions with an agent for giving surface hydrophilic property or fabrication condltions for fibers, they may be applied to the first fibers and the second fibers. Among them, for the first fibers, a hydrophilic treatment using a surface active agent is preferred, since the durability against water can be easily controlled and is economically advantageous in view of its cost as well. For the hydrophilic surface treatment of the hydrophobic fibers, a method of giving hydrophilic property in a production step of the fibers is customary. But, according to another example~ non-woven fabrics may be prepared by using the hydrophobic synthetic fibers described above, and the hydrophilic property may be glven to a surface of the hydrophobic fibers by applylng a chemical or physical surface modificatlon or treating with a solution of a surface active agent, after fabrication of the non-woven fabrics.
For the hydrophobic fibers, polyesters to which various kinds of surface treatment can be applied and which are less expensive are preferred as both of the first fibers and the second fibers. Furthermore, for the first fibers, polyolefinic fibers to which a hydrophilic treatment with low durability can be easily applled by a surface active agent and whlch are also useful as a thermo-fusible binder are also preferred.

In accordance with the fiber composition and the layer constitution as described above, the non-woven fabrics can provide those performances of rapidly absorbing the liquid into the absorbing layer and restricting the return of liquid from the absorbing layer, which performances conflict with each other, can be achieved simultaneously.
Now, descriptions will be made specifically below of conditions to attain the foregoing properties of the non-woven fabrics most effectively.
The thickness of the non-woven fabric layer is one of ma~or factors of the return of liquid from the absorbing layer to outside of the non-woven fabric layer. That is, if the non-woven fabric layer ls too thin, the dlstance between the ~kin and the absorblng layer is extremely small when the absorbing article is wet. This increases the liquid return and significantly worsens wearer's feeling. On the other hand, if the non-woven fabric layer is made thick, the liquid return surely decreases. However, if the non-woven fabric layer is too thick, the entire absorbing article becomes thick, gives an abnormal feeling to a wearer and also increases a manufacturing cost. Further, if the surface layer is very thick, the thickness of a layer that becomes more hydrophobic once water has permeated through the non-woven fabrics is very large and water dropped next time hardly intruded to inside of the non-woven fabrics.

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- 12 - 65702-~64 Thus, the thickness of the non-woven fabrics should be within a most adequate range in view of the liquid-returning property, feeling upon use and production cost. The adequate range of thickness varies depending on application uses. The entire thickness is desirably from 0.3 mm to 0.8 mm under a load of 2.S
g/cm when using the non-woven fabrics for a sanitary napkin and from 0.6 to 2.5 mm when using them for a paper diaper.
In order to produce the non-woven fabrics having the thickness as descrlbed above, it is necessary to adequately select fibers for constituting the non-woven fabrics and to provide the non-woven fabrics with an appropriate weight per unit area. At first, it is necessary to use hydrophobic synthetic fibers having a surface rendered hydrophilic which show no remarkable reduction in the bulkiness upon wetting as has been described above. The size of the fibers may be wlthin a range from 1.5 to 6 denier, because lt is difficult to increase the bulkiness (i.e., volume) of the entire non-woven fabrics if the size is less than 1.5 denier, whereas the entire non-woven fabrics become rigid and worsen the feelings lf the size exceeds 6 denier. Further, although a higher weight per unit area is generally preferable for providing the non-woven fabrics with the bulkiness, lt is desired on the other hand to suppress the weight per area as low as possible when the production coæt is taken into consideration.

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Accordingly, it is preferable that the fibers have an elasticity as high as possible, which can be attained, for example, by a method of avoidinq the use of extremely fine fibers as described above or selecting hollow fibers or those fibers applied with sterical crimping.
Thus, if ease of control of the durability of surface hydrophilic treatment to water, low cost, ease of imparting a high elasticity and ease of fabrication of a non-woven fabric are required, then fibers made of polyester and polyolefin are most suitable as fibers for non-woven fabrics.
Referring to the weight per unit of the non-woven fabrics, since the thickness is small when the weight per unit àrea is low, whereas the thickness is large when the weight per unit is high as a general trend, an adequate range should be chosen depending on appllcation uses. Where the fibers as described above used, the weight per unit is desirably within the range from 10 to 30 g/m2 as a whole and from 5 to 10 g/m2 for the surface layer in the case of using them as sanitary napkins, and is from 20 to 50 g/m2 as a whole and from 7 to 15 g~m2 for the surface layer in the case of using them as paper diapers.
Referring finally to a method of stabilizing webs, any of the methods can be selected as long as they have such a nature that the surface hydrophilic property of the constltuent fibers is greater in the second fibers than in the first fibers in the situation where the non-woven fabrics are finally formed. However, C

~.297~38 - 14 - 65702-26g in the case where the hydrophilic treatment to the fiber surface undergoes damages in the course of forming the non-woven fabrics as in the entanglement by the high speed water flow, the hydrophilic property has to be provided by the after-treatment as described above, which requires much labours and brings about an extreme difficulty. Accordingly, for forming the non-woven fabrics without degrading the hydrophilic property of the starting fiber material, it is desirable to set the fibers to each other by the thermal fusion of the fibers. Further, the method of forming the non-woven fabrics stabilized by the fusion of the fibers is excellent as compared with other methods also in that C

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12~638 the fabrics have sterically stabilized skeletons and can attain the physical property (thickness, feelings) of the nGn-woven fabrics as described above efficiency ~with no remarkable increase in the weight per unit area).
The invention will now be described in more detail by way of the Examples.

Example 1 - 17 and Comparative Example 1 - 7 (Fibers and non-woven fibers) Using fibers shown in Table 1 as the first fibers and the second fibers, various kinds of non-woven fabrics shown in Tables 2 and 3 were manufactured.
The method of processing the fibers with an agent for provlding hydrophilic property (which may hereinafter be simply referred to as a hydrophilic agent) shown in Table 1 are as below:
(A) Fibers were immersed in an aqueous solution of ~2S~

a surface active agent and then dewatered and dried.
(B) The hydrophilic agent was dispersed in a solvent, into which the fibers were immersed, then dewatered and dried followed by heat treatment (140 C for 30 minutes).
(C) The hydrophilic agent was dispersed in a solvent, into which the fibers immersed, then dewatered and dried followed by heat treatment (170 C for 10 minutes).
(D) The procedures were according to Example 1 of Japanese Patent Laid-Open No. Sho 55-122074.
(E) After placing fibers in a bell jar made of glass and evacuating the inside of the bell jar to lower than 10 Torr, an exhaust valve was closed and air was supplied up to 0.1 mmHg. Then, vapors of the hydrophilic agent were supplied up to 0.5 % based on the weight of the fibers and high frequency voltage (13.56 MHz) was applied to electrodes for about 3 minutes.
(F) Commercially available fibers were used as they are.

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(G) Commercially available fibers were used as they are.
(H) Commercially available fibers were used as they are.
(I) Commercially available polyethylene - polypropylene composite fibers were washed with warmed water, dewatered and then dried.
In Examples 1 - 16 and Comparative Examples 1 - 6, non-woven fabrics were manufactured by way of heat bonding method (passing a hot blow at 140 C to a card web and setting ES fibers to other ribers through fusing by using polyethylene - polypropylene composite fibers)(ES fibers) or low melting polyester - polyester composite fibers (Melt~) as binder fibers. In Example 17, fibers of the web were entangled under a high pressure water flow (spray pressure at 55 kg/cm2, average amount Or water stream supplied in the lateral direction : 250 cc/cm.min) to r^r~
non-woven rabrics. Then, after applying the same hydrophilic processing as in (B) above, the hydrophilic agent described in (A) above was sprayed from the side of the rirst layer and then dried. In Comparative Example 7, the riber webs were subjected to the high pressure water flow processing under the same conditions as described above into non-woven fabrics, which were not applied with the hydrophilic treatment by the after treatment.
(Specimens for Measurement) Commercially available sanitary napkins (trade mark;
Lorie, manuractured by Kao Co) and disposable pape~ diapers - ~2~

- 1~ - 5702-264 (trade mar~ Merries, manuractured by Kao Co.) were used while removing non-woven fabrics therefrom and, instead, placing non-woven fabrics shown in Tables 2 and 3 thereover respectively as the specimens to be measured as absorbing articles assuming the sanitary napkins and disposable paper diapers. Examples 1 - 7, Examples 9 - 17 and Compara-tive Examples 1 - 7 were used for the sanitary napkins, while Example 8 was used for the disposable paper diapers.
(Test Method) (1) Surface liquid flow :
Test solution was dropped from above 1 cm of the surface of the specimen inclined by 45 and the flowing distance along the surface of the non-woven fabrics from the point of dropping to the point where the solution was absorbed to the inside of the specimen was measured, which was defined as the surface liquid flow for the first time.
Then, one minute after the dropping of the test solutiont the test solution was again dropped to a portion where the solution had been dropped previously and the flowing dis-tance along the surface of the non-woven fabrics from the point of dropping to the point where the solution was absorbed to the inside of the specimen was measured, which was defined as the surface liquid flow for the second time. Those showing short surface liquid flow for the first time and the surface liquid flow for the second time showing no considerable change indicate tbat there was no , ...... .

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- l9 - 5702-264 remarkable lateral lea~. The dropping condition was 0.1 g/sec for the specimen assuming the sanitary napkins and 0.5 g/cm for the specimen assuming the paper diapers.
(2) Returning amount :
The test solution was caused to be absorbed by 10 cc in the specimens assuming the sanitary napkin and by 150 cc in the specimens assuming the paper diaper, pressure was applied after a predetermined of time and the amount of the test solution returned from the inside through the non-woven fabrics was measured. As the returning amount is smaller, surface stickiness is reduced, the feeling upon use is better and wiping e~fect is more excellent.
(3) Water absorption amount :
Using the apparatus as shown in Figure 1, in which fiber webs 1 were packed at a density of 0.13 g~cm3 into a glass tube 2 of 14 mm inner diameter, ion exchanged water 5 was caused to be absorbed through a glass filter 4 by the fiber webs under a constant hydraulic pressure (atmospheric pressure) in a head portion 3 and the water absorption amount (ml) after one minute was measured. The water absorption amount in the dry state is defined as Hd, while the water absorption amount after passing 600 cc of the ion exchanged water through the fiber webs and then dried was defined as Hw. Greater Hw means higher sur~ace hydro-philic property after wetting.

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(Effect of the Invention) As can be seen from Examples, the surfa~e liquid flow in the absorbing articles according to this invention is low both at the first and the second times and the liquid return from the inside to the surface is also low.
In Comparative Examples 1 - 7, absorbing articles were manufactured and the surface liquid flow and the liquid return thereof were measured by using the non-woven fabrics out of the range according to this invention and by the same procedures as in Examples. Since fibers having no substantial hydrophilic property were used for the surface layers in Comparative Example 1, 3 and 4, the surface liquid flow is high and leakage is liable to be caused. In Comparative Example 2 is constituted up to 100 Z
with fibers which are hydrophilic at the surface and the inside and the returning amount is remarkable and sticki-ness is liable to occur although the surface liquid flow is preferable.
In Examples 2 - 17 and Comparative Examples 5 and 6, the fabrics are constituted with fibers having a hydro-philic surface and a hydrophobic inside and show lower returning amount as compared with Example 1 comprising fibers having hydrophilic surface and inside. However, Comparative Example 5, among them, has a lower mixing ratio of the second fibers in the rearface layer than that defined in this invention and the sur~ace liquid ~low at , .. . .

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the second time is increased. Further, in Comparative Example 6, the m.ixing ratio of the second fibers in the surrace layer is greater than the range as defined in this invention and, accordingly, the returning amount is increased.
In Comparative Example 7, the surface hydrophilic treatment undergoes damage by the high speed water rlow to remarkably reduce the hydrophilic property and, as a result, the surrace liquid flow is increased.

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Claims

1. An absorbent article comprising:
a non-woven fabric layer which is to be in contact with skin when the absorbent article is in use; and an absorbent material behind the non-woven fabric layer, wherein the non-woven fabric layer comprises:
(1) a surface layer comprising 60 to 100 percent by weight of first fibers having a hydrophilic surface portion and a hydrophobic inside portion and from 40 to zero percent by weight of second fibers which are hydrophilic at least at the surface thereof, and (2) a back layer containing at least one layer comprising from zero to 50 percent by weight of said first fibers and from 100 to 50 percent by weight of said second fibers, said second fibers being more hydrophilic at the surface than said first fibers after getting wet.

2. The absorbent article as claimed in Claim 1, in which the surface layer solely consists of the first fibers.

3. The absorbent article as claimed in Claim 1, in which said first fibers have been formed by making the surface of hydrophobic fibers hydrophilic and the second fibers are hydrophilic fibers themselves or have been formed by making the surface of hydrophobic fibers hydrophilic.

4. The absorbent article as claimed in Claim 1, 2 or 3, in which the first fibers, when first wetted and then dried have a surface hydrophilicity of not more than 0.5 ml and the second fibers, when first wetted and then dried, have a surface hydrophilicity of 1 to 2 ml, wherein the surface hydrophilicity is defined by the amount of water (in ml) absorbed by the fibers through a glass filter placed at the bottom thereof when the fibers packed at a density of 0.13 g/cm3 in an uprightly standing glass tube having an inner diameter of 14 mm are left under atmospheric water pressure at the bottom for one minute.

5.. An absorbent article as claimed in Claim 1, 2 or 3, which is a sanitary napkin or a disposable diaper, and further comprises a leak-proof material layer such that the absorbent material is between the non-woven fabric layer and the leak-proof material layer.

6. A sanitary napkin or disposable diaper comprising:
a leak-proof material layer;
a non-woven fabric layer which comes into contact with the skin of a wearer when the napkin or diaper is in use;
and an absorbent material layer between the leak-proof layer and the non-woven fabric layer;
wherein the non-woven fabric layer comprises:

(1) a surface layer of first fibers, said first fibers being synthetic and having a hydrophilic surface portion and a hydrophobic inside portion, and (2) a back layer of second fibers, said second fibers being regenerated or synthetic and having a hydrophilic surface portion and either a hydrophilic or hydrophobic inside portion, said second fibers being more hydrophilic at the surface than said first fibers after being wetted.

7. The napkin or diaper as claimed in Claim 6, in which said first fibers have been formed by making the surface of hydrophobic fibers hydrophilic and the second fibers are hydrophilic fibers themselves or have been formed by making the surface of hydrophobic fibers hydrophilic.

8. The napkin or diaper as claimed in Claim 7, in which the first fibers, when first wetted and then dried, have a surface hydrophilicity of not more than 0.5 ml and the second fibers, when first wetted and then dried, have a surface hydrophilicity of 1 to 2 ml, wherein the surface hydrophilicity is defined by the amount of water (in ml) absorbed by the fibers through a glass filter placed at the bottom thereof when the fibers packed at a density of 0.13 g/cm3 in an uprightly standing glass tube having an inner diameter of 14 mm are left under atmospheric water pressure at the bottom for one minute.

9. The napkin or diaper as claimed in Claim 7, in which the first fibers are synthetic hydrophobic fibers whose surface has been rendered hydrophilic; and the synthetic fibers are selected from the group consisting of polyethylene, polypropylene, polyester, polyamide and polyacrylonitrile, and the second fibers are rayon or synthetic hydrophobic fibers whose surface has been rendered hydrophilic; and the synthetic hydrophobic fibers are selected from the group consisting of polyester, polyamide and polyacrylonitrile.

10. The napkin or diaper as claimed in Claim 7, 8 or 9, wherein the surface of the first fibers has been rendered hydrophilic by treating the surface with a surface active agent.

11. A disposable diaper comprising:
a leak-proof material layer;
a non-woven fabric layer which comes into contact with skin of a wearer when the diaper is in use; and an absorbent material layer between the leak-proof layer and the non-woven fabric layer, wherein the non-woven fabric layer has a thickness of about 0.6 to 2.5 mm and comprises:
(1) a surface layer comprising 60 to 100 percent by weight;
first synthetic hydrophobic fibers of a size of about 1.5 to 6 denier having a surface rendered hydrophilic and not showing remarkable reduction of bulkiness upon wetting, and 40 to zero percent by weight of second fibers which are rayon or second hydrophobic synthetic fibers of a size of about 1.5 to 6 denier having a surface rendered hydrophilic and not showing remarkable reduction of bulkiness upon wetting, and (2) a back layer comprising zero to 60 percent by weight of said first synthetic hydrophobic fibers and 100 to 50 percent by weight of rayon or said second hydrophobic synthetic fibers, the surface of said rayon or second hydrophobic synthetic fibers being more hydrophilic than the surface of said first synthetic fibers after getting wet.

12. The disposable diaper as claimed in Claim 11, in which said first hydrophobic fibers are polyethylene, polypropylene, polyester, polyamide, polyacrylonitrile or a mixture thereof.

13. The disposable diaper as claimed in Claim 12, in which said back layer comprises zero to 50 percent by weight of said first synthetic fibers and 100 to 50 percent by weight of rayon or said second hydrophobic synthetic fibers which are polyester, polyamide, polyacrylonitrile or a mixture thereof.

14. The disposable diaper as claimed in Claim 13, in which said first hydrophobic fibers are a polyolefin selected from the group consisting of polyethylene, polypropylene and polyethylene-polypropylene composite;

15. The disposable diaper as claimed in Claim 14, in which the surface of said first hydrophobic fibers has been rendered hydrophilic by treating with a surfactant, a polyalkylene group-containing polyester oligomer, polyvinyl alcohol or a hydrophilic copolymer type epoxy modified silicone.

16. The disposable diaper as claimed in Claim 12, 13 or 14, in which the first fibers, when first wetted and then dried, have a surface hydrophilicity of not more than 0.5 ml and the rayon or second fibers, when first wetted and then dried, have a surface hydrophilicity of 1 to 2 ml, wherein the surface hydrophilicity is defined by the amount of water (in ml) absorbed by the fibers through a glass filter placed at the bottom thereof when the fibers packed at a density of 0.13 g/cm3 in an uprightly standing glass tube having an inner diameter of 14 mm are left under atmospheric water pressure at the bottom for one minute.