JP2006043998A - Nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonwoven fabric which is excellent in water absorbency and has suppressed water permeability. <P>SOLUTION: The nonwoven fabric has a one-way arrangement nonwoven fabric in which thermoplastic resin filaments are arranged in one direction or a laminated nonwoven fabric in which two one-way arrangement nonwoven fabrics are laminated so that the filament arrangement directions of the nonwoven fabrics cross at right angles. The diameters of the filaments are 3-20 μm, the bulk density is at least 0.1 g/cm<SP>3</SP>, and the basis weight is 5-40 g/cm<SP>2</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nonwoven fabric that is excellent in water absorption but has suppressed water permeability.

  2. Description of the Related Art Conventionally, liquid absorbing parts such as diapers and sanitary products have been provided with an intermediate layer between the liquid absorber and the surface layer in order to improve liquid absorbency and improve reversal. Patent Document 1 mentions hydrolytic paper, airlaid pulp, and hydrolyzable nonwoven fabric as specific examples of the intermediate layer.

  In general, the function of the intermediate layer is to allow the liquid that has entered through the surface layer to permeate efficiently and be absorbed by the liquid absorber, and further, the liquid that has oozed out of the liquid absorber goes out through the surface material. That is, to prevent the liquid from returning. When the surface layer or the intermediate layer is composed of a nonwoven fabric, it is effective to increase the fiber diameter of the nonwoven fabric and reduce the bulk density in order to allow the liquid to permeate efficiently. In fact, such a nonwoven fabric is used for the surface layer and intermediate layer of diapers and sanitary products on the market. However, the nonwoven fabric with such a large fiber diameter and small bulk density is excellent in the ability to permeate the liquid into the liquid absorber, but also easily permeates the liquid that has oozed out of the liquid absorber. In addition, it was insufficient to suppress the liquid from returning.

Further, if the liquid intrusion into the liquid absorber is local, the liquid absorption into the liquid absorber is also local, and the liquid absorber cannot be used efficiently. Therefore, in order to improve the liquid diffusibility of the liquid absorbing portion, a conventional diaper or sanitary product has a diffusing material such as water absorbent paper disposed in front of the liquid absorber. This type of diffusion material is excellent in liquid absorbency, but the fiber direction is random and the diffusion direction cannot be controlled. Further, since the bulk density is high, the diffusion range is narrow (the diffusion distance is small). For the purpose of compensating for this drawback, Patent Document 2 discloses that a spunbonded nonwoven fabric having a basis weight of 10 to 50 g / m ² subjected to a hydrophilic treatment is further disposed before water-absorbing paper. In addition, the nonwoven fabric which devised the embossing pattern is arranged, or the nonwoven fabric with a high fabric weight is also arranged. However, disposing another nonwoven fabric in this way has the disadvantage that it is bulky and thick, and that moisture permeability and air permeability are reduced and heat retention is high, so that it is easily steamed.

  On the other hand, examples of the nonwoven fabric include a spunbond nonwoven fabric manufactured by a spunbond method and a meltblown nonwoven fabric manufactured by a meltblown method.

  A spunbonded nonwoven fabric is a random nonwoven fabric in which filaments are oriented in random directions. For this reason, the spunbonded nonwoven fabric has low strength and it is difficult to highly arrange the filaments. In order to improve this point, Patent Document 3 describes a method of inclining the conveyor with respect to the ejection direction of the filament. Further, in Patent Document 4, filaments ejected together with an air flow are deposited on a breathable conveyor, and a means for blocking the air flow is provided on the back side of the conveyor to control the air flow, whereby the filaments are arranged in the vertical direction. And a method for improving the arrangement in the vertical direction is described. Furthermore, Patent Document 5 discloses that the filaments are arranged in the lateral direction by curving a part of the conveyor in a direction perpendicular to the traveling direction and downward, or by providing a barrier immediately above the conveyor. ing.

Since the melt blown nonwoven fabric is thinned by the high-speed airflow before the filaments are solidified, very thin filaments having a diameter of 5 μm or less can be obtained.
JP 2001-190597 A JP-A-8-164159 Japanese Patent Publication No. 60-25541 Japanese Patent Laid-Open No. 7-3604 Japanese Patent No. 2612203

  However, in the conventional spunbonded nonwoven fabric, the methods disclosed in the above-mentioned documents are not sufficient for highly arranging filaments, and even if a web, which is an aggregate of filaments collected on a conveyor, is stretched. The filaments are widened and defibrated, and the filaments cannot be highly drawn.

  Further, the melt blown nonwoven fabric is easily cut when the filament is thinned, and the length of the filament is shorter than that of the spunbond nonwoven fabric. Therefore, the melt-blown nonwoven fabric cannot be highly stretched even when a web, which is an aggregate of filaments collected on a conveyor, is stretched.

  In such a state, even if the bulk density is increased by compression processing or the like in order to improve the liquid absorbency, the filaments are not highly arranged and the filaments are often overlapped. Sex cannot be obtained. In addition, the filaments are easily cut where the filaments overlap, leading to a significant decrease in strength as a nonwoven fabric.

  This invention is made | formed in view of the problem of the prior art mentioned above, and aims at providing the nonwoven fabric which was excellent in water absorption and suppressed water permeability.

In order to achieve the above object, the nonwoven fabric of the present invention is a unidirectionally arranged nonwoven fabric in which filaments spun from a thermoplastic resin are arranged in one direction, or two unidirectionally arranged nonwoven fabrics so that the arrangement direction of the filaments is orthogonal to each other. The filaments have a diameter of 3 to 20 μm and a bulk density of 0.1 g / cm ³ or more.

According to the nonwoven fabric of the present invention, since the filaments are arranged in one direction and the bulk density is 0.1 g / cm ³ or more, the air layer in the nonwoven fabric is thin and there is little overlap of the filaments. As a result, it is possible to obtain a non-woven fabric having excellent water absorption but having a water permeability according to JIS A1218 of 0.1 cm / sec or less. Further, since the filament diameter is in the above range, the filaments can be easily arranged at a high level, and the bulk density can be increased so that desired water absorption and water permeability can be obtained. Furthermore, since the nonwoven fabric of the present invention has low water permeability and the filaments are arranged in one direction, it is excellent in liquid diffusibility and controllability in the diffusion direction.

  As described above, since the nonwoven fabric of the present invention has excellent water absorption and the reversion of absorbed liquid is suppressed, the nonwoven fabric can be made suitable for use in liquid absorbing parts such as diapers and sanitary products. it can. In addition, because it has excellent liquid diffusibility and controllability of the diffusion direction, the liquid absorber can be used effectively when used in combination with the liquid absorber, thereby reducing the amount of liquid absorber used. can do. Furthermore, since the non-woven fabric of the present invention has moderate moisture permeability and air permeability and a low heat retention rate, when used in close contact with the body, the non-woven fabric has a comfortable wearing feeling. be able to.

  Next, an embodiment of the present invention will be described.

The nonwoven fabric of this embodiment is a stretched unidirectional array nonwoven fabric in which filaments (fibers) spun from a thermoplastic resin are arranged in approximately one direction and stretched in the filament arrangement direction, or configured as described above. In addition, an orthogonal laminated nonwoven fabric obtained by laminating two stretched unidirectionally arranged nonwoven fabrics so that the arrangement directions of the filaments are orthogonal to each other. The diameter of the filament constituting the stretched unidirectionally aligned nonwoven fabric needs to be 3 to 20 μm, preferably 3 to 15 μm. Further, the bulk density needs to be 0.1 g / cm ³ or more, and preferably 0.2 g / cm ³ or more. The basis weight is 5 to 40 g / cm ² .

  The non-woven fabric configured as described above is a non-woven fabric whose water permeability is suppressed to 0.1 cm / sec or less while having excellent water absorption. Moreover, the heat retention rate is 30% or less, preferably 25% or less, and such a nonwoven fabric can be particularly preferably used as a liquid absorbent for diapers and sanitary products.

  Here, the stretched unidirectionally aligned nonwoven fabric will be described.

  As described above, the stretched unidirectionally aligned nonwoven fabric is obtained by stretching filaments in the aligned direction, and in the spinning stage, a filament having the same thickness as that of a normal nonwoven fabric is spun. The filament diameter is set to 3 to 20 μm by stretching the film to 10 to 10 times. In this case, the filaments are unoriented at the spinning stage, and the accumulated filaments are arranged in a certain direction. Will improve. However, since the filament arrangement at the spinning stage is not complete, the stretched unidirectionally aligned nonwoven fabric is slightly mixed with unstretched filaments and unoriented filaments. The unstretched filament has a low melting point and melts in the subsequent laminating process, so that it functions as an adhesive between the filaments of the stretched unidirectionally aligned nonwoven fabric.

  Filaments constituting the stretched unidirectionally arranged nonwoven fabric are long fiber filaments. The long fiber filament referred to here may be a substantially long fiber and has an average length exceeding 100 mm. The length and diameter of the filament are measured by a micrograph.

  The stretched unidirectionally aligned nonwoven fabric includes a longitudinally stretched nonwoven fabric and a laterally stretched nonwoven fabric depending on the production method. In the present embodiment, any of these can be used, and the combination is also free. The longitudinally stretched nonwoven fabric is a nonwoven fabric in which filaments are arranged and stretched in the longitudinal direction, which is the feed direction when producing the nonwoven fabric, and the transversely stretched nonwoven fabric is a direction perpendicular to the feed direction when producing the nonwoven fabric. A nonwoven fabric in which filaments are arranged and stretched in the transverse direction.

  The longitudinally stretched nonwoven fabric and the laterally stretched nonwoven fabric will be described in detail.

  The longitudinally stretched non-woven fabric gives draft tension to the spun filament to reduce the filament diameter, and then accumulates on the conveyor by using the movement of the conveyor to form a web in which the filaments are arranged in the longitudinal direction. This is obtained by stretching in the longitudinal direction.

  Examples of a method for giving draft tension to the filament include a melt blow method (MB method) and a narrowly defined spunbond method (SB method). In any method, hot air is sprayed onto the filament in order to minimize molecular orientation when reducing the diameter of the filament. In addition, in order to improve the arrangement of the filaments on the conveyor, the filament is spun while being inclined with respect to the conveyor conveying surface, or a rod member is arranged in the hot air flow area, and the rod member is rotated or moved. It is preferable to vibrate the filament in the longitudinal direction using the Coanda effect generated by the above.

  The web accumulated on the conveyor is stretched in the longitudinal direction to form a longitudinally stretched nonwoven fabric. This stretching further improves the alignment of the filaments.

  Although the web may be fully stretched in one stage, multistage stretching is mainly used. In multistage stretching, the first stage of stretching is performed as preliminary stretching immediately after spinning, and the second and subsequent stages of stretching are performed as main stretching.

  As a web stretching method, a proximity stretching method is preferably used. When the proximity stretching method is used in the multistage stretching, the proximity stretching is used for the first stage stretching. The proximity stretching method is a method of stretching while maintaining a short distance between stretches (distance from the starting point of stretching to the end point) in a method of stretching the web by the difference in surface speed between two adjacent sets of rolls, It is desirable that the distance between stretching is 100 mm or less. Thus, individual filaments can be effectively stretched by stretching the web by the proximity stretching method. In particular, when the filaments are arranged in the longitudinal direction as a whole but are bent to some extent, keeping the distance between the draws as short as possible is important for effectively drawing the individual filaments.

  In a general melt blown nonwoven fabric, filaments are randomly arranged, and even if the filaments are stretched by the proximity stretching method, the probability that individual filaments are stretched is low only by increasing the spacing between the filaments. However, in the present invention, since the webs are already arranged in one direction at a high degree, according to the proximity drawing method, individual filaments can be drawn more reliably.

  Next, the transversely stretched nonwoven fabric will be described. In order to produce a transversely stretched nonwoven fabric, first, a web in which filaments are arranged in the transverse direction is formed. The web in which the filaments are arranged in the horizontal direction is obtained by shaking the filaments spun from the spinning nozzles in the horizontal direction by directly ejecting air from the air ejection holes arranged around the spinning nozzles and collecting them on the conveyor. Can be formed. As another method, there is a method in which the filaments are vibrated in the lateral direction using the Coanda effect described above and accumulated on a conveyor. In this way, the filaments are accumulated on the conveyor in a state where there are many arrangement components in the lateral direction.

  By stretching the web thus obtained in the filament arrangement direction, that is, in the transverse direction, a transversely stretched nonwoven fabric is obtained. This stretching further improves the alignment of the filaments.

  Examples of the method of stretching the web in the transverse direction include a tenter method and a pulley method. The tenter method is generally used as a method for widening a film or the like, but requires a large floor area for installation of equipment, and it is difficult to change the product width and the magnification ratio. The stretch ratio of the nonwoven fabric must be changed according to the application. Therefore, it is preferable to use a pulley system in which these changes can be easily performed even during operation. In any of the stretching methods, the stretching in the lateral direction is performed with both ends of the web being held. Since the filaments are already arranged in the web in a state where there are many arrangement components in the transverse direction, individual filaments can be effectively drawn in these drawing methods.

  A typical method for producing a stretched unidirectionally aligned nonwoven fabric has been described by taking a longitudinally stretched nonwoven fabric and a laterally stretched nonwoven fabric as examples. However, the method for producing a stretched unidirectionally aligned nonwoven fabric is not limited to the method described above, and a filament Any method can be used as long as the filaments are arranged in substantially one direction and the arranged filaments can be stretched in the arrangement direction.

  As described above, the orthogonal laminated nonwoven fabric is obtained by laminating two stretched unidirectionally arranged nonwoven fabrics so that the arrangement direction of the filaments is perpendicular to each other. Each of the transversely stretched nonwoven fabrics can be used as it is. As a result, two stretched unidirectionally aligned nonwoven fabrics can be continuously drawn out and overlapped to obtain a continuous and uniform orthogonal laminated nonwoven fabric. In addition, a vertically stretched nonwoven fabric is prepared in advance, and at the production stage of the laterally stretched nonwoven fabric, the vertically stretched nonwoven fabric is drawn out and stacked on the laterally stretched nonwoven fabric in the course of transporting the laterally stretched nonwoven fabric, and these are laminated to form an orthogonally laminated nonwoven fabric. Can be manufactured more efficiently.

  Two stretched unidirectionally aligned nonwoven fabrics can be laminated by, for example, a hot embossing method. The embossing conditions vary depending on the type of resin used for the stretched unidirectionally aligned nonwoven fabric, but are preferably set to a temperature 30 to 80 ° C. lower than the melting point. Moreover, when high surface smoothness is requested | required of an orthogonal lamination nonwoven fabric, lamination | stacking of two extending | stretching one-way arrangement | sequence nonwoven fabrics can also be performed by a thermal calendar process.

As described above, the diameter of the filament constituting the nonwoven fabric needs to be in the range of 3 to 20 μm. If the diameter of the filament is less than 3 μm, it becomes difficult to arrange the filaments in one direction due to insufficient strength of the filament and shortening of the filament as in the case of the meltblown nonwoven fabric. Furthermore, when the filament diameter is less than 3 μm, it becomes difficult to arrange the filaments at a high level, so the overlap of the filaments increases and the bulk density cannot be reduced, so that the desired water absorption and heat retention rate can be obtained. Becomes difficult. The target water absorption is 10 minutes or less, preferably 8 minutes or less, according to the test method shown in the examples described later. The target heat retention rate is a heat retention rate measured according to JIS L1096A method of 30% or less, preferably 25% or less. On the other hand, when the filament diameter exceeds 20 μm, even if the filaments are highly arranged and the bulk density is 0.1 g / cm ³ or more, the distance between the filaments becomes large and it is difficult to obtain the desired water permeability. become. The target water permeability is such that the water permeability measured according to JIS A1218 is 0.1 cm / sec or less, preferably 0.05 cm / sec or less.

The bulk density of the nonwoven fabric needs to be 0.1 g / cm ³ or more. When the bulk density is less than 0.1 g / cm ³ , it becomes difficult to achieve the above-described water absorption, water permeability, and heat retention.

  Further, in the stretched unidirectionally arranged nonwoven fabric, the filaments are arranged in almost one direction, and the bulk density is effective for checking the degree of arrangement of the filaments. That is, as the number of overlapping filaments increases, the thickness increases and the bulk density decreases. On the other hand, if the filaments are arranged in one direction, the overlapping of the filaments is small, thereby reducing the thickness and increasing the bulk density.

  Although the nonwoven fabric of this embodiment has high water absorption, the principle which water absorption becomes high here is considered as follows. In the water absorption test method described in this specification, since the nonwoven fabric is immersed in water, both surfaces of the nonwoven fabric are in contact with water. When the nonwoven fabric is viewed microscopically, a filament having a certain thickness is located at a certain distance, so water between the filaments depends on the interfacial tension and the pressure relationship between the water and the air in the nonwoven fabric. It is in a fixed state. In order for water to penetrate into the nonwoven fabric, it is necessary for the water soaked from both sides to come into contact with each other. However, in a nonwoven fabric having a low bulk density, the air layer in the nonwoven fabric is thick and the water soaked from both sides is unlikely to come into contact. On the other hand, the nonwoven fabric of this embodiment has a high bulk density and a small amount of filament overlap, so the air layer in the nonwoven fabric is thin, and water soaked from both sides when immersed in water easily comes into contact with water. To absorb. Further, when a material having high water absorption (high absorbent material) such as a polymer absorber or water absorbent paper is closely attached to one side and liquid is present on the opposite side, the same applies to this embodiment. The water absorption of the nonwoven fabric (in this case, the liquid permeability to the high-absorbent material on one side) is increased.

  Furthermore, for the reversal of the liquid absorbed in the superabsorbent, the nonwoven fabric of this embodiment has low water permeability, so that water disintegration paper, airlaid pulp, water disintegrating nonwoven fabric used in commercially available diapers and sanitary products, It can be remarkably improved as compared with a hydrophilic nonwoven fabric or the like.

  Moreover, the nonwoven fabric of this embodiment is excellent in control of the direction which diffuses the diffusibility of a liquid. This is because of the low water permeability, the permeation of the liquid dripping on the surface of the nonwoven fabric is suppressed, and the gap between the highly arranged filaments causes capillary action, and the liquid is diffused along the filament arrangement direction. This is probably because of this. Thereby, the nonwoven fabric of the present embodiment exhibits excellent liquid diffusibility and regulates the arrangement direction of the filaments, or by adjusting the amount of filaments in the longitudinal direction and the transverse direction in the orthogonal laminated nonwoven fabric, The direction in which the liquid diffuses can be controlled.

The basis weight of the nonwoven fabric is 5 to 40 g / cm ² . When the basis weight is less than 5 g / cm ² , it becomes difficult to obtain a desired water permeability. On the other hand, when the basis weight exceeds 40 g / cm ² , it becomes difficult to obtain desired water absorption and heat retention.

  Regarding the air permeability, the air permeability of the nonwoven fabric of this embodiment is lower than that of a spunbonded nonwoven fabric having the same basis weight. Therefore, when trying to obtain the same air permeability, it is necessary to make the basis weight lower than that of the spunbonded nonwoven fabric. Moreover, about the moisture permeability, the nonwoven fabric of this embodiment can obtain the moisture permeability equivalent to a spunbond nonwoven fabric with the same basis weight.

  The raw material of the nonwoven fabric is not particularly limited. For example, a polyester resin, a polyamide resin, a polypropylene resin, a polyethylene resin, or the like can be used, and a mixture of two or more kinds of resins may be used. If necessary, additives such as antioxidants, weathering agents, lubricants, antiblocking agents, flame retardants, nucleating agents, antistatic agents, pigments, and inorganic fillers can be added to these resins.

  You may give a secondary process to the nonwoven fabric in the range which does not impair the characteristic. Examples of secondary processing include hydrophilic processing, embossing, and composite (bonding) with other materials. Examples of other materials combined with the nonwoven fabric include spunbond nonwoven fabric, melt blown nonwoven fabric, and spunlace nonwoven fabric. In addition, as a lamination method at the time of compounding, a nonwoven fabric such as a thermocompression bonding method, an extrusion lamination method, a dry lamination method, adhesion by an adhesive, a method of applying a low melting point resin and thermocompression bonding, a method of physically tangling a filament, etc. Various methods generally used for laminating can be applied.

  The nonwoven fabric of the present invention thus obtained and the processed product thereof can be used for various applications. Uses include diapers, sanitary napkins, incontinence pads, skin care wipers, kitchen wipers, cleaning wipers, poultice bases, bandages, gauze, medical supporters, disposable towels, sweat pads, face masks, filters, training pants Paper diapers, medical drape gowns and drapes, interlining, underwear, disposable underwear and apparel, tape base fabrics, percutaneous absorbent base materials, and the like, but are not limited thereto.

  As described above, the nonwoven fabric of the present invention is excellent in water absorption and water permeability is suppressed, so that it can be particularly preferably used for liquid absorbing parts such as diapers and sanitary products. When the non-woven fabric of the present invention is used for such a liquid absorbing portion, it exhibits excellent liquid absorbability, and the reversal of the liquid once absorbed is significantly improved as compared with currently marketed products. Furthermore, since the current commercial product has insufficient liquid diffusibility, the liquid absorber is not sufficiently functioned and utilized, and as a result, the amount of liquid absorber used increases. This not only wastes material, but also significantly reduces the wear between the users. On the other hand, the non-woven fabric of the present invention can control the diffusibility of the liquid by the arrangement of the filaments, so that the liquid can be diffused entirely without concentrating only on a part of the liquid absorber. Therefore, the usage amount of the liquid absorber can be reduced.

  Further, when the nonwoven fabric of the present invention is used for the outermost layer (back sheet) of a diaper or sanitary product, it has moisture permeability and air permeability, but has low heat retention properties, so that there is an effect that the inside becomes difficult to be muggy.

  The above-described properties of the nonwoven fabric of the present invention not only make the diaper and sanitary product users comfortable, but can also reduce the materials used, greatly contributing to resource and energy savings.

  Hereinafter, specific examples of the present invention will be described together with comparative examples.

<Example 1>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction was prepared with a basis weight of 5 g / cm ² , a filament diameter of about 10 μm, and a bulk density of 0.23 g / cm ³ .

<Example 2>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction with a basis weight of 10 g / cm ² , a filament diameter of about 10 μm, and a bulk density of 0.25 g / cm ³ was produced.

<Example 3>
Laminating a longitudinally stretched nonwoven fabric in which filaments are arranged in the longitudinal direction and a transversely stretched nonwoven fabric in which filaments are arranged in the transverse direction with a basis weight of 10 g / cm ² , a filament diameter of about 7 to 14 μm, and a bulk density of 0.3 g / cm ³ An orthogonal laminated nonwoven fabric was produced. The longitudinally stretched nonwoven fabric and the laterally stretched nonwoven fabric were substantially the same except for the arrangement direction of the filaments.

<Example 4>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction was prepared with a basis weight of 10 g / cm ² , a filament diameter of about 10 μm, and a bulk density of 0.26 g / cm ^3. Further, embossing was performed on the longitudinally stretched nonwoven fabric.

<Example 5>
A laminate of a longitudinally stretched nonwoven fabric in which filaments are arranged in the longitudinal direction and a transversely stretched nonwoven fabric in which filaments are arranged in the transverse direction with a basis weight of 10 g / cm ² , a filament diameter of about 7 to 14 μm, and a bulk density of 0.31 g / cm ³ The orthogonal laminated nonwoven fabric was produced, and further, the produced orthogonal laminated nonwoven fabric was embossed. The longitudinally stretched nonwoven fabric and the laterally stretched nonwoven fabric were substantially the same except for the arrangement direction of the filaments.

<Example 6>
A laminate of a longitudinally stretched nonwoven fabric in which filaments are arranged in the longitudinal direction and a transversely stretched nonwoven fabric in which filaments are arranged in the transverse direction with a basis weight of 20 g / cm ² , a filament diameter of about 7 to 14 μm, and a bulk density of 0.35 g / cm ³ An orthogonal laminated nonwoven fabric was produced. The longitudinally stretched nonwoven fabric and the laterally stretched nonwoven fabric were substantially the same except for the arrangement direction of the filaments.

<Example 7>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction was prepared with a basis weight of 40 g / cm ² , a filament diameter of about 7 to 14 μm, and a bulk density of 0.45 g / cm ³ .

<Example 8>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction with a basis weight of 10 g / cm ² , a filament diameter of about 7 to 14 μm, and a bulk density of 0.28 g / cm ³ was produced.

<Example 9>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction was prepared with a basis weight of 15 g / cm ² , a filament diameter of about 14 to 18 μm, and a bulk density of 0.28 g / cm ³ .

<Comparative example 1>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction with a basis weight of 3 g / cm ² , a filament diameter of about 10 μm, and a bulk density of 0.18 g / cm ³ was produced.

<Comparative example 2>
A longitudinally stretched nonwoven fabric in which filaments were arranged in the longitudinal direction with a basis weight of 50 g / cm ² , a filament diameter of about 10 μm, and a bulk density of 0.55 g / cm ³ was produced.

<Comparative Example 3>
A longitudinally stretched nonwoven fabric having a basis weight of 10 g / cm ² , a filament diameter of about 30 μm, a bulk density of 0.28 g / cm ³ and filaments arranged in the longitudinal direction was prepared, and the prepared longitudinally stretched nonwoven fabric was embossed.

<Comparative example 4>
A spunbonded nonwoven fabric having a basis weight of 20 g / cm ² , a filament diameter of about 15 μm, a bulk density of 0.08 g / cm ³ and a random filament arrangement was produced.

<Comparative Example 5>
A melt-blown nonwoven fabric having a basis weight of 15 g / cm ² , a filament diameter of about 2 μm, a bulk density of 0.13 g / cm ³ and a random filament arrangement was produced.

<Evaluation>
The following characteristics were evaluated for Examples 1 to 9 and Comparative Examples 1 to 5.

<Water absorption>
Immerse the test piece cut into 10cm x 15cm in water,
(Weight after water absorption-weight before water absorption) × 100 / Time until the water absorption rate (%) calculated by weight before water absorption reaches 50% or more is measured, and the time is used as an index indicating water absorption. did.

<Water permeability>
According to JIS A1218, the test was conducted with a water permeable area of 1 cm ² , a water level of 10 cm, and a water permeable time of 60 sec.

<Heat retention rate>
In accordance with the JIS L1096A method, an ASTM type moisture retention tester was used, and the test plate area was 225 cm ² , the test plate temperature was 36 ± 0.3 ° C., the outside air temperature was about 20 ° C., and the test time was 120 minutes.

<Liquid diffusibility>
The maximum diffusion distance of spread when a drop of physiological saline colored with water-soluble red ink was dropped on the test piece, and the vertical and horizontal diffusion ratios were estimated. Since the liquid did not penetrate due to the surface tension, water was previously contained in the test piece.

<Reversibility of liquid>
This evaluation was performed in comparison with a commercially available sanitary napkin (manufactured by Kao Corporation, sanitary napkin “Laurier (registered trademark) Super Slim Guard”). The test sample was produced as follows. The nonwoven fabric between the surface nonwoven fabric of the sanitary napkin and the liquid absorbent was peeled off, and replaced with Examples 1 to 9 and Comparative Examples 1 to 5, respectively. Immediately after absorbing 5 ml of physiological saline colored with water-soluble red ink from the surface layer on the test sample thus prepared, a tissue paper was placed on the surface layer, and a load of 200 g was further applied thereon. Then, the degree of physiological saline adhering to the tissue paper was judged visually. The evaluation was performed in five stages according to the following criteria based on the reversal state with a commercially available sanitary napkin.
Level 1: worse than commercial products.
Level 2: Equivalent to a commercial product.
Level 3: Less adhesion than commercial products.
Level 4: Significantly less adhesion than commercial products.
Level 5: No adhesion.

  In Table 1, the evaluation result about Examples 1-9 and Comparative Examples 1-5 is shown.

Claims (2)

A unidirectionally arranged nonwoven fabric in which filaments spun from a thermoplastic resin are arranged in one direction, or a laminated nonwoven fabric in which two unidirectionally arranged nonwoven fabrics are laminated so that the arrangement direction of the filaments is orthogonal,
A nonwoven fabric in which the filament has a diameter of 3 to 20 μm, a bulk density of 0.1 g / cm ³ or more, and a basis weight of 5 to 40 g / cm ² . The nonwoven fabric according to claim 1, wherein the heat retention is 30% or less.