Background Art A spun bond nonwoven fabric, a typical example of the filament nonwoven fabric is manufactured by introducing a group of filaments discharged from a melt spinning spinneret into an air sucker to draw the group of filaments, distributing the group of filaments to integrate it on a collecting conveyor to obtain a filament web, and then entangling or thermally melting and adhering the filaments by a suitable method. Therefore, the spun bond nonwoven fabric comprises filaments, that is continuous fibers, so that it is superior in mechanical properties such as tensile strength to staple fiber nonwoven fabrics comprising staple fibers. Also, the filaments obtained by melt spinning are directly distributed and integrated to obtain a nonwoven fabric, and therefore the spun bond nonwoven fabrics can be produced more efficiently than the nonwoven fabrics obtained by distributing and integrating staple fibers by a dry or wet method, resulting in high productivity. Recently, the yield of the spun bond nonwoven fabrics has increased greatly.

In particular, a conjugated filament nonwoven fabric using a polymer containing an ethylene-vinyl acetate copolymer or a saponified material thereof as a first component and using a crystalline thermoplastic polymer as a second component has an excellent thermal melting and adhering property in addition to the above advantages of the filament nonwoven fabrics. Therefore, said conjugated filament nonwoven fabric has good processability. In addition, said conjugated filament nonwoven fabric has a more excellent thermal melting and adhering property with other materials than the conjugated filament nonwoven fabric using an olefin type low melting point copolymer, in which two or more types of olefin are copolymerized, as the first component, and therefore the former does not require a binder. If said nonwoven fabric has good quality in total, its application field will be wide since it can be laminated with other materials by adhesion, and therefore a significant increase in demand is expected.

Containing an ethylene-vinyl acetate copolymer or a saponified material thereof, the conjugated filament nonwoven fabric has a low crystalline property, and a lower melting point or a lower softening point.

Also, the value of the frictional resistance between the filaments or between the filament and the surface of a machine made of metal is relatively high, though the value depends on the copolymer containing an ethylene-vinyl acetate copolymer or a saponified material thereof. Therefore, when the filaments discharged from spinning nozzle holes are drawn by an air sucker made of metal, due to the friction between the filament and the surface of the air sucker or between the filaments, unevenness in the filament fineness occurs, and the filaments form a bundle so that they are not easily distributed.

Also, when using such a polymer having low crystalline property, it takes long time significantly for the filaments of the polymer discharged from the spinning nozzle holes in a melting state to crystallize and solidify.

Therefore, due to the friction, the filaments form a bundle so that the filament which include the copolymer having a low melting point or a low softening point contacts in a melted state before it solidifies. Therefore, so-called filament breakage occurs, degrading its operation performance.

Publication of Japanese Unexamined Patent Application No. 5- 5261 discloses a nonwoven fabric comprising conjugated filaments of an ethylene-propylene random copolymer and isotactic polypropylene.

However, this publication does not particularly describe a way to solve the above problems. Also, this publication does not propose a method for solving the above problems in a filament nonwoven fabric comprising conjugated filaments containing an ethylene-vinyl acetate copolymer having properties different from those of the copolymer containing an ethylene-propylene random copolymer or a saponified material thereof as one component.

In order to solve the above problems, the present invention seeks to provide a filament nonwoven fabric comprising conjugated filaments containing a copolymer containing an ethylene-vinyl acetate copolymer or a saponified material thereof as one component, in which a highly adhesive property and low temperature adhesive property are good, in which the flexibility, the feeling such as touch feeling, and the uniformity of the obtained filament nonwoven fabric are excellent, and in which operation performance such as spinning performance is good.

As a result of close examination, we have found that by at least adding an inorganic substance powder to the first component that is a low melting point or low softening point component, the inorganic substance powder is exposed on the surface of the filament to provide fine roughness to the surface of the filament, reducing the contact point between the filaments, so that the filaments can be prevented from sticking to each other during spinning. Therefore, the filament breakage is reduced, providing good operation performance. Also, the crystallization temperature of the polymer of the first component increases little even with the addition of the inorganic substance powder, and an increase in crystallinity is significantly small . Thus, a filament nonwoven fabric is obtained in which the characteristics of the copolymer containing a low melting point or low softening point ethylene-vinyl acetate copolymer or a saponified material thereof, such as flexibility, highly adhesive property, and low temperature adhesive property are not degraded, in which flexibility and feeling such as touch feeling are good, and in which the adhesive property with other members is excellent, leading to the present invention.

Disclosure of Invention In order to solve the above problems, the filament nonwoven fabric of the present invention comprises thermal melting and adhering conjugated filaments comprising a first component containing an ethylene-vinyl acetate copolymer or a saponified material thereof that forms at least a part of a surface of the filament in a direction of a length of the filament and a second component comprising a crystalline thermoplastic polymer having a higher melting point than the first component, wherein at least the first component contains an inorganic substance powder, a content of the inorganic substance powder being at a concentration of 500 to 50,000 weight ppm in the filament.

In the filament nonwoven fabric of the present invention, it is preferred that the ratio of vinyl acetate or a saponified material thereof in the ethylene-vinyl acetate copolymer is 5 to 40 wt. %.

In the filament nonwoven fabric of the present invention, it is preferred that the percentage content of the ethylene-vinyl acetate copolymer or the saponified material thereof in the polymer component of the first component is 5 wt. % or more.

In the filament nonwoven fabric of the present invention, it is preferred that a polymer mixed with the ethylene-vinyl acetate copolymer or the saponified material thereof in the first component is polyethylene.

In the filament nonwoven fabric of the present invention, it is preferred that a weight average particle size of the inorganic substance powder is 0.04 to 2 m.

In the filament nonwoven fabric of the present invention, it is preferred that the inorganic substance powder is at least one type of inorganic powder selected from the group consisting of titanium dioxide, silica, alum, calcium carbonate, calcium oxide, magnesium oxide, and talc.

In the filament nonwoven fabric of the present invention, it is preferred that the crystalline thermoplastic polymer of the second component is polypropylene.

In the filament nonwoven fabric of the present invention, it is preferred that the crystalline thermoplastic polymer of the second component is polyethylene terephthalate.

In the filament nonwoven fabric of the present invention, it is preferred that the filament nonwoven fabric is obtained by a spun bond method.

In the filament nonwoven fabric of the present invention, it is preferred that a volume ratio of the first component to the second component is in the range of 10:90 to 90:10. More preferable range is 30:70 to 70:30.

Next, the absorbent article of the present invention uses the filament nonwoven fabric of the present invention in at least a part of the article.

According to the filament nonwoven fabric of the present invention, the disadvantages in the conventional filament nonwoven fabrics are improved so that a filament nonwoven fabric comprising conjugated filaments can be provided in which a highly adhesive property and low temperature adhesive property are good, in which the flexibility, the feeling such as touch feeling, and the uniformity of the obtained filament nonwoven fabric are excellent, and in which operation performance such as spinning performance is good.

Therefore, its industrial value is very great. In other words, by at least adding an inorganic substance powder to the first component that is a low melting point or low softening point component, fine roughness is provided to the surface of the filament, preventing the filaments from sticking to each other during spinning. Therefore, the filament breakage is reduced, providing good operation performance. Also, the inorganic substance powder provides relatively small nucleating action, the crystallization temperature of the polymer component containing an ethylene-vinyl acetate copolymer or a saponified material thereof increases little, and the increase in crystallinity is significantly small Thus, a filament nonwoven fabric can be provided in which the characteristics of the copolymer having a low melting point or low softening point, such as flexibility, highly adhesive property, and low temperature adhesive property are not degraded, in which flexibility and feeling such as touch feeling are good, and in which the adhesive property with other members are excellent.

In the filament nonwoven fabric of the present invention, a preferred mode in which a ratio of a vinyl acetate or a saponified material thereof is 5 to 40 wt. % in its ethylene-vinyl acetate copolymer or its saponified material thereof. The melting point of said copolymer is not too low, thermal stability is good, and melt spinning can be performed without change in quality, heat degradation or the like.

Also, the thermal adhesive property with other different types of materials is excellent. In addition, the softness specific to copolymers can be provided well. Furthermore, the inorganic substance powder is exposed on the surface of the filament to provide fine roughness to the surface, so that the conjugated filaments do not form a bundle easily, unevenness in the filament fineness is minor, distributability is excellent, and filament breakage does not occur easily. Therefore, spinning performance can be improved.

In the filament nonwoven fabric of the present invention, according to a preferred mode in which a percentage content of the ethylene-vinyl acetate copolymer or the saponified material thereof in the polymer component of the first component is 5 wt. % or more, low temperature adhesive property and the thermal adhesive property with other different types of materials can be provided stably. Also, the softness specific to copolymers can be provided well, and a filament nonwoven fabric providing an excellent feeling can be provided.

In the filament nonwoven fabric of the present invention, according to a preferred mode in which a weight average particle size of the inorganic substance powder is 0.04 to 2 ij m, the inorganic substance powder having a weight average particle size of this range provides a lesser increase in cost than that having a smaller particle size, does not cause secondary aggregation, clogging of the filter or the spinning nozzle, or filament breakage, and therefore does not degrade the operation performance. Also, such an inorganic substance powder, compared with that having a larger particle size, does not cause degradation in the dispersion property of the inorganic substance powder, clogging of the filter or the spinning nozzle, or filament breakage, and therefore does not degrade the operation performance.

Thus, the above effects can be fully achieved.

In the filament nonwoven fabric of the present invention according to a preferred mode in which the inorganic substance powder is at least one type of inorganic powder selected from the group consisting of titanium dioxide, silica, alum, calcium carbonate, calcium oxide, magnesium oxide, and talc, these inorganic substance powders provide relatively small nucleating action, the crystallization temperature of the polymer of the first component containing an ethylene-vinyl acetate copolymer or a saponified material thereof increases little, and the increase in crystallinity is very small. Thus, a filament nonwoven fabric can be obtained in which the characteristics of the polymer having a low melting point or low softening point, i.e.

the first component, such as flexibility, highly adhesive property, and low temperature adhesive property are not easily degraded, flexibility and feeling such as touch feeling are good, and the adhesive property with other members is excellent.

In the filament nonwoven fabric of the present invention, according to a preferred mode in which the crystalline thermoplastic polymer of the second component is polypropylene, a relatively flexible filament nonwoven fabric can be obtained.

In the filament nonwoven fabric of the present invention according to a preferred mode in which the crystalline thermoplastic polymer of the second component is polyethylene terephthalate, a filament nonwoven fabric can be obtained in which tenacity is higher and elasticity (cushion property) in crimping is more excellent.

In the filament nonwoven fabric of the present invention, according to a preferred mode in which the filament nonwoven fabric is obtained by a spun bond method, a nonwoven fabric having excellent mechanical properties such as tensile strength can be easily obtained.

Also, the filaments obtained by melt spinning are directly distributed and collected to obtain a nonwoven fabric. Therefore, the productivity is very high. In addition, the above action and effect are effectively provided particularly by the spun bond method. Therefore, the conventional disadvantages in the conjugated filament nonwoven fabrics obtained by the spun bond method can be effectively improved.

Brief Description of Drawings Fig. 1 shows a plan view of an example of a disposable diaper partially using the filament nonwoven fabric of the present invention in unwrapped form, as seen from the skin side; Fig. 2 shows a schematic cross-section end view taken on line I-I of Fig. 1; Fig. 3 shows a schematic cross-section end view taken on line II-II of Fig. 1; Fig. 4 shows a plan view of an example of a sanitary napkin partially using the filament nonwoven fabric of the present invention in unwrapped form, as seen from the skin side; and Fig. 5 shows a schematic cross-section end view taken on line 111-111 of Fig. 4.

Best Mode for Carrying Out the Invention The filament nonwoven fabric of the present invention comprises thermal melting and adhering conjugated filaments comprising a first component containing an ethylene-vinyl acetate copolymer or a saponified material thereof that forms at least a part of a surface of the filament in the direction of the length of the filament and a second component comprising a crystalline thermoplastic polymer having a higher melting point than the first component, wherein at least the first component contains an inorganic substance powder, the content of the inorganic substance powder being at a concentration of 500 to 50,000 weight ppm in the filament. Here, it is preferred that the area of the first component forming at least a part of a surface of the filament is continuous over the entire length.

Suitable examples of the conjugated filaments comprising a polymer containing an ethylene-vinyl acetate copolymer or a saponified material thereof that forms at least a part of a surface of the filament in the direction of the length of the filament as a first component and a crystalline thermoplastic polymer as a second component include sheath-core type conjugated filaments comprising a sheath component as a first component and a core component as a second component, eccentric sheath-core type conjugated filaments in which the position of the core component in the cross-section of the sheath-core type filament is eccentric, and parallel type conjugated filaments (side-by-side type conjugated filaments) in which the first and second components are laminated. In particular, with the eccentric sheath-core type conjugated filaments and the parallel type conjugated filaments, crimped filaments can be easily obtained, so that a filament nonwoven fabric that is bulky and provides good feeling can be obtained. The ratio of the first component to the second component (combination ratio) in the cross-section of the parallel type conjugated filament may be 1 : 1, or one component may have a larger cross-sectional area in the cross-section of the filament than the other component.

The volume ratio of the first component to the second component of the conjugated filament (corresponding to the area ratio of the cross-section when comprising the cross-section of the filament, that is, the combination ratio) is generally 10:90 to 90:10, preferably 30:70 to 70:30.

In the present invention, a polymer containing an ethylene- vinyl acetate copolymer or a saponified material thereof is used as the first component.

Ethylene-vinyl acetate copolymers in which the ratio of a vinyl acetate or a saponified material thereof (that is, the copolymerization proportion of the vinyl acetate component) is about 5 to 40 wt. % are preferably used as a first component in the present invention. In particular, ethylene-vinyl acetate binary copolymers are more preferably used. However, a minor amount of another component may be copolymerized without defeating the object of the present invention.

The ethylene-vinyl acetate copolymers in which the ratio of a vinyl acetate or a saponified material thereof is about 5 to 40 wt. % do not have an excessively low melting point or stickiness, satisfying the properties required for the material disposed to the surface of the filament. Also, such ethylene-vinyl acetate copolymers have relatively high thermal stability, and therefore the problems of pyrolysis and change in quality are few in melt spinning. In addition, such ethylene-vinyl acetate copolymers are excellent in thermal adhesive property with other different types of materials, which is a characteristic of ethylene-vinyl acetate copolymers. The same is true of the saponified material thereof.

The above ethylene-vinyl acetate copolymers used in the present invention can be used without saponification, or a saponified material thereof can be used. The saponification degree may be any up to 100 %. In other words, a partly saponified material may be used.

The saponified materials require a somewhat higher cost, but it provides good feeling. When using the saponified material of an ethylene-vinyl acetate copolymer, the ratio of a vinyl acetate or a saponified material thereof in the ethylene-vinyl acetate copolymer is preferably in the range of 5 to 40 wt. % in total for the above reasons.

For example, when the saponification degree is 0 %, "5 to 40 wt. %" indicates the copolymerization proportion of the vinyl acetate. When the saponification degree is 100 %, "5 to 40 wt. %" indicates the copolymerization proportion of the component of the saponified vinyl acetate material.

Also, the polymer component of the first component preferably contains 5 wt. % or more of the ethylene-vinyl acetate copolymer or the saponified material thereof based on the total weight of the polymer component in the first component for maintaining a good low temperature adhesive property and a good adhesive property with other different types of materials. The ethylene-vinyl acetate copolymer or the saponified material thereof can be used in the ratio up to 100 wt. % based on the total weight of the polymer component in the first component. Also, it can be mixed with a polymer having a relatively low melting point or softening point in a possible range for melt spinning as required.

Among the polymers having a relatively low melting point or softening point mixed with the ethylene-vinyl acetate copolymer or the saponified material thereof in the first component, polyethylene is preferred to ensure compatibility and a low melting point temperature.

Various polyethylenes can be used, and in particular, low density polyethylene is more preferred. By using polyethylene, the friction with metal such as an air sucker as described above can be further reduced during melt spinning, and the adhesion between the filaments can be more suitably prevented.

The first component containing the ethylene-vinyl acetate copolymer or the saponified material thereof used in the present invention may be any component that can thermally melt or soften at a temperature lower than that of the crystalline thermoplastic polymer of the second component to provide the thermal melting and adhering property, and preferably it can thermally melt or soften at a temperature 5"C or more lower than the temperature at which the crystalline thermoplastic polymer of the second component thermally melts or softens, more preferably, 30 "C or more lower. Such components do not cause damage, such as degradation in physical property due to heat, to the second component when the obtained filament fleece is thermally melted and adhered.

A crystalline thermoplastic polymer that has a higher melting point or softening point than the component containing the ethylene- vinyl acetate copolymer or the saponified material thereof in the first component and can be used for conjugated filament spinning with the first component is used as the crystalline thermoplastic polymer of the second component in the present invention. Preferably, polypropylene or polyethylene terephthalate is used. When using polypropylene as the second component, a relatively flexible filament nonwoven fabric can be obtained. When using polyethylene terephthalate as the second component, a filament nonwoven fabric having a higher tenacity and a higher elasticity (cushion property) in crimping can be obtained.

The MFR (melt flow rate) of the polymer used need not be limited to a specific value. However, the first and second components both (provided that an olefin polymer is used as the second component) generally have a MFR of 10 to 100 g/10 min.

The inorganic substance powder used in the present invention may be any inorganic substance powder as long as it can provide roughness on the surface of the filament and prevent the stickiness between the filaments.

The weight average particle size of the inorganic substance powder is preferably 0.04 to 2 u m, more preferably 0.04 to 1 g m. If the particle size of the inorganic substance powder is too small, the cost will be high, and secondary aggregation, clogging of the filter or the spinning nozzle, and filament breakage will easily occur, degrading the operation performance. If the particle size of the inorganic substance powder is too large, the dispersion property of the inorganic substance powder will deteriorate, clogging of the filter or the spinning nozzle and filament breakage will easily occur, degrading the operation performance. Therefore, the above range is more preferred. The particle size of the inorganic substance powder can be measured by observation with an electron microscope. For the measurement of the particle size of the inorganic substance powder contained in the conjugated filament, for example, the inorganic substance powder can be measured by observation with the electron microscope after separating the polymer and the inorganic substance powder of the conjugated filament by heating the conjugated filament under vacuum.

For the particle size of a particle having a shape other than a spherical shape, the particle size of a sphere having the same volume as the particle is calculated.

Concrete examples of the inorganic substance powders used in the present invention include various stable and inactive inorganic substance powders such as titanium dioxide, silica, alum, calcium carbonate, calcium oxide, magnesium oxide, and talc. These inorganic substance powders can provide fine roughness to the surface of the conjugated filament. Therefore, the stickiness between the filaments is prevented during spinning. Also, the unevenness in the filament fineness and the distributability is good, and the filament breakage is improved, resulting in good operation performance as described above in conjugated filament nonwoven fabrics such as spun bond nonwoven fabrics. In addition, these inorganic substance powders have a relatively small nucleating action. Therefore, the filament nonwoven fabric can be obtained in which the characteristics of the first component, the polymer component containing an ethylene-vinyl acetate copolymer or a saponified material thereof having a low melting point or highly adhesive property, such as flexibility, highly adhesive property, and low temperature adhesive property are not degraded, and in which flexibility and feeling such as touch feeling are good, and in which the adhesive property with other members is excellent. In particular, titanium dioxide, silica, alum, calcium carbonate, calcium oxide, magnesium oxide, and talc are preferable because they have a smaller nucleating action. These inorganic powders may be used as pure powders. However, the cost will be high from the industrial point of view. Therefore, these inorganic substance powders containing impurities may be used as long as they do not defeat the object of the present invention. Either rutile type titanium dioxide or anatase type titanium dioxide can be used. However, the rutile type titanium dioxide is preferred because of its good weather resistance and heat resistance. Also, the inorganic substance powder should be added at least to the first component. The powder may be added to both the first and second components.

The inorganic substance powder may be introduced in the side feeder of an extruder to be melt extruded and added with kneading.

Also, the inorganic substance powder may be added in the form of a compound or a master batch in which the powder and the first component are previously kneaded, for example. In kneading this inorganic substance powder, a suitable dispersing agent for improving the dispersibility is usually used. Examples of the dispersing agents for the inorganic substance powder include surfactants.

The inorganic substance powder should be contained in the filament at a concentration of 500 to 50,000 weight ppm. If the amount of the added inorganic substance powder is far less than this amount, the effect of preventing the filaments from sticking to each other during spinning, the effect caused by providing fine roughness to the surface of the filament, will not be fully provided, so that the filaments will form a bundle due to friction, causing unevenness in the filament fineness, distributing failure, or filament breakage, and therefore degrading the operation performance. If the amount of the added inorganic substance powder is far greater than the above amount, clogging of the filter or the spinning nozzle or filament breakage will occur, degrading the operation performance. When using the filament nonwoven fabric of the present invention especially for sanitary napkins, the inorganic substance powder is preferably added at a concentration of 12,000 weight ppm or less in the total amount of the polymer component.

For conjugated filaments, the concentration of the added inorganic substance powder in the filament refers to the concentration in the entire filament. Therefore, even if the inorganic substance powder is added only to the first component, the concentration indicates the average concentration in the entire conjugated filament comprising the first and second components.

In the present invention, the fineness of the conjugated filament of the nonwoven fabric need not be limited to a specific value.

A conjugated filament having suitable fineness may be used according to the types and applications of the material polymers used.

Preferably, the fineness is about 1 to 8 d/f. The fineness is preferably 1 to 5 d/f for sanitary materials such as paper diapers, sanitary napkins, incontinent pads, surgical garments, surgical drapes, and base clothes for a hap agent.

The basis weight of the filament nonwoven fabric of the present invention need not be limited to a specific value. A nonwoven fabric having a suitable basis weight may be used according to the types and applications of the material polymers used. Preferably, the basis weight is about 10 to 50 g/m2. The basis weight is preferably about 10 to 30 g/m2 especially for sanitary materials.

The filament nonwoven fabric according to the present invention can be obtained by using the polymer compositions of the first and second components as described above for melt spinning to obtain a conjugated filament from the spinneret. Such a filament nonwoven fabric can be easily manufactured by a well-known spun bond method.

The detailed explanation of the spun bond method is omitted because the method is already well known. For example, a mixture of low melting point polymer component containing an ethylene-vinyl acetate copolymer or a saponified material thereof and an inorganic substance powder is prepared as the first component, and a crystalline thermoplastic polymer (a crystalline thermoplastic polymer with which the inorganic substance powder is mixed may be used as required) is prepared as the second component. These polymer compositions are put into individual extruders and melt spun using the conjugated filament spinneret. A group of non-drawn filaments discharged from the spinneret is introduced into the air sucker to be drawn to obtain a group of drawn filaments. Then, the group of the drawn filaments discharged from the air sucker is charged with a suitable charging apparatus such as a corona discharge apparatus, and then distributed by passing the group of filaments between a pair of vibrating blade-like members (flaps) or by colliding the group with a suitable plate. The group of the distributed filaments is collected as a filament fleece on an endless net-like conveyor with a suction apparatus provided on its back surface. The collected filament fleece is conveyed on the endless conveyor, and introduced between the pressed rolls of a point bond machine comprising heated embossing and smooth rolls, where the first component of the filament fleece melts or softens in the area corresponding to the convex portion of the embossing roll so that the filaments thermally melt and adhere to each other to obtain a filament nonwoven fabric. The basis weight of the filament nonwoven fabric is controlled by controlling the spinning discharge speed (discharge weight per hour) or the travelling speed of the endless conveyor, for example. The method for turning a filament fleece into a nonwoven fabric (entangling or thermally melting and adhering) need not be limited to the point bond method. Other methods such as a hot air heating method, a high pressure water stream method, a needle punching method, and an ultrasonic heating method may be used. Also, these methods can be combined.

The filament nonwoven fabric of the present invention need not be limited to that manufactured by the above methods. However, the spun bond method is preferred because nonwoven fabrics having high mechanical properties such as tensile strength can be easily obtained, and because the filaments obtained by melt spinning can be directly distributed and collected to obtain a nonwoven fabric, resulting in very high productivity and low cost for manufacturing.

The thus obtained filament nonwoven fabric of the present invention has a highly adhesive property, a low temperature adhesive property, and a good adhesive property with different types of materials.

The obtained filament nonwoven fabric has high flexibility, excellent feeling such as touch feeling, and high uniformity. Also, the filament nonwoven fabric comprises conjugated filaments providing good operation performance such as spinning performance. Therefore, the filament nonwoven fabric can be used for various applications.

Especially, the nonwoven fabric can be thermally adhered easily when bonded or adhered to other materials or combined with other materials for forming a composite material, and therefore the nonwoven fabric can be effectively used for manufacturing such a composite material.

Furthermore, the filament nonwoven fabric of the present invention can be used for a part of absorbent articles such as sanitary napkins and disposable diapers.

In order to absorb body fluid such as urine or blood and prevent the body fluid from leaking, the absorbent articles including disposable diapers such as paper diapers and sanitary napkins at least comprises a liquid absorbent layer for absorbing and holding body fluid such as urine or blood, a liquid permeable front cover of a nonwoven fabric or the like located on the surface side of the liquid absorbent layer (the side to contact skin), and a liquid impermeable back sheet located on the back side for preventing the absorbed body fluid from leaking outside, though the elements somewhat differ according to the specific aspects of the absorbent articles. Also, such absorbent articles usually comprise water repellent side sheets of a nonwoven fabric or the like provided on both sides of the absorbent article in addition to the back sheet in order to prevent the liquid such as the absorbed body fluid from leaking when the position of the absorbent article is displaced from a predetermined position for wear by the movement of the body or when the wearer lies on his side (In disposable diapers or the like, the side sheet is often gathered, and therefore it is called side gathers or a leg cuff. In disposable diapers, the side sheets are provided in such a position that they surround and hold the groin or the thighs when the disposable diaper is worn). Also, in disposable diapers, a water repellent round sheet of a nonwoven fabric or the like is further provided on the skin sides of the portion covering the abdominal region and the portion covering the upper hips on the opposite side so as to prevent the liquid such as the absorbed body fluid from leaking outside the absorbent article on the abdominal region or the upper hips as the wearer moves, for example, falls down, lies down, or turns his body. Furthermore, in some disposable diapers, band-like waist gathers or the like are provided on the waist position skin side, and these also comprises a water repellent sheet of a nonwoven fabric or the like.

Also, a suitable liquid absorbent layer is formed by mixing an aggregate of fibers comprising cellulose fibers such as a fluff pulp, and synthetic fibers as required, with a highly absorbent polymer, and hardening the mixture by compressing. This liquid absorbent layer is usually wrapped in tissue paper or the like. Also, a thermoplastic film is usually used for the back sheet. The thermoplastic film generally has innumerable micropores to provide air permeability in order to prevent the inside of the absorbent article from becoming stuffy when it is worn. Also, a thermoplastic film combined with a nonwoven fabric is used in the viewpoint of improving the feel and appearance of the plastic specific to films and improving the tenacity. In addition, a multi-layered thermoplastic film with other sheets further inserted for providing other various functions is used.

The above filament nonwoven fabric of the present invention can be used for the front cover, the side sheet, the round sheet, part of the back sheet (laminated with a liquid impermeable sheet, or the like), the liquid absorbent layer and the like of these absorbent articles according to their purposes. For the liquid absorbent layer, the filament nonwoven fabric is inserted in the middle of the liquid absorbent layer and thermally adhered, for example. Therefore, the filament nonwoven fabric can provide the reinforcing action of preventing the liquid absorbent layer from breaking due to the stress caused by the body movement with the body weight during wearing, without inhibiting the absorbent property of the liquid absorbent layer much. These members are suitably thermally adhered and fixed where required.

Also, partial point adhesion that can perform a number of point adhesions is preferably used as heat pressing or thermo-compression bonding depending on the parts.

Where the filament nonwoven fabric according to the present invention is used in absorbent articles will be described below by illustrating typical examples with reference to the drawings. However, the structures of the absorbent articles shown are only examples, and the structures of absorbent articles need not be limited to the structures shown.

Fig. 1 shows a plan view of an example of a disposable diaper seen from the skin side; Fig. 2 shows a schematic cross-section end view taken on line I-I of the example; and Fig. 3 shows the schematic cross- section end view taken on line II-II of the example.

In Figs. 1-3, 1 and 1' denote liquid absorbent layers for absorbing and holding body fluid. The liquid absorbent layer is not limited to a specific layer, and is formed by mixing an aggregate of fibers comprising cellulose fibers such as a fluff pulp, and synthetic fibers as required, with a highly absorbent polymer, and hardening the mixture by compressing. The liquid absorbent layers 1 and 1' are wrapped in tissue paper or the like (not shown). In this manner of the present invention, a reinforcement layer 6 of the filament nonwoven fabric of the present invention is inserted between the liquid absorbent layers 1 and 1' to thermally adhere between the liquid absorbent layers 1 and 1' to serve as reinforcement so that the liquid absorbent layers do not break due to the body weight or the movement of the body. 2 denotes a liquid permeable front cover located on the surface side of the liquid absorbent layer (the side to contact the skin). The filament nonwoven fabric of the present invention also can be used for this front cover 2. 3 denotes a back sheet requiring liquid impermeability. The filament nonwoven fabric of the present invention is laminated on the back side of this back sheet 3 as a back sheet laminate 8. By laminating the filament nonwoven fabric on the back sheet of such an absorbent article, the cold feel of the plastic film and the appearance specific to the plastic can be improved to provide the warm feel and appearance like cloth, and the back sheet can be reinforced.

A round sheet 4 is not always necessary. In Figs. 2-3, the round sheet 4 is provided between the liquid absorbent layer 1' and the back sheet 3. The filament nonwoven fabric of the present invention also can be used as the round sheet 4. 5 and 5' denote water repellent side sheets provided on both sides of the absorbent article in order to prevent liquid such as absorbed body fluid from leaking when the position of the absorbent article is displaced from a predetermined position for wear by the movement of the body or when the wearer lies on his side as mentioned above (In disposable diapers or the like, the side sheet is often gathered, and therefore it is called side gathers or a leg cuff. In disposable diapers, the side sheets are provided in such a position that they surround and hold the groin or the thighs.). The filament nonwoven fabric of the present invention also can be used for this side sheet. Band-like waist gathers may be provided on the waist position skin side as denoted by 7 in Fig. 1, though they are not shown in Figs. 2 and 3. The filament nonwoven fabric of the present invention also can be used for the waist gathers. Suitable parts of these members are thermally adhered so that they do not drop, though such description is omitted in the drawings. If the filament nonwoven fabric of the present invention is used as the member to be thermally adhered, the member can be thermally adhered without hot melt adhesives. Since a specific straight-chain high fatty acid and/or a metal salt thereof is added to the filament material of the filament nonwoven fabric of the present invention as described above, sliminess is reduced, and therefore an absorbent article providing good feeling can be obtained.

The filament nonwoven fabric of the present invention need not be used for all the members described above. The filament nonwoven fabric may be used for one or more of the members.

Fig. 4 shows a plan view of an example of a sanitary napkin seen from the skin side; and Fig. 5 shows a schematic cross-section end view taken on line III-III of the example. 1 and 1' denote liquid absorbent layers wrapped in tissue paper (not shown). 2 denotes a liquid permeable front cover located on the surface side of the liquid absorbent layer (the side to contact the skin). 3 denotes a back sheet requiring liquid impermeability. 5 and 5' denote side sheets. In this manner of the present invention, a reinforcement layer 6 of the filament nonwoven fabric of the present invention is inserted between the liquid absorbent layers 1 and 1' to thermally adhere between the liquid absorbent layers 1 and 1' to serve as reinforcement so that the liquid absorbent layers do not break due to the body weight or the movement of the body. Also, the filament nonwoven fabric of the present invention is laminated on the back side of the back sheet 3 as a back sheet laminate. The filament nonwoven fabric of the present invention also is used for the side sheets 5 and 5'.

Suitable parts of these members are thermally adhered so that they do not drop, though such description is omitted in the drawings.

If the filament nonwoven fabric of the present invention is used for the member requiring the thermal adhesion, the member can be thermally adhered without hot melt adhesives. In the filament nonwoven fabric of the present invention, sliminess is reduced as described above, and an absorbent article providing good feeling can be obtained.

The filament nonwoven fabric of the present invention need not be used for all the members as described above. The filament nonwoven fabric may be used for one or more of the members as described above for the above example.

In the filament nonwoven fabric of the present invention, sliminess is reduced, and therefore an absorbent article providing good feeling can be obtained. If the filament nonwoven fabric of the present invention is used for the member requiring bonding, the member can be thermally adhered easily without hot melt adhesives. Therefore, an absorbent article can be obtained at low cost with little weight increase.

[Examples] The present invention will be more specifically described below by way of Examples and Comparative Examples. However, the present invention need not be limited to these Examples.

Examples 1-11 and Comparative Examples 1-3 A mixed polymer containing an ethylene-vinyl acetate binary copolymer or a saponified material thereof (a polymer mixed with the above polymer is low density polyethylene and is abbreviated as LDPE in Table 1) and an inorganic substance powder shown in Table 1 were prepared as the first component.

A crystalline thermoplastic polymer shown in Table 1 was prepared as the second component.

These polymer compositions were put in individual extruders having a diameter of 60 mm. The first component was extruded from the extruder at an extrusion temperature of 220"C. For the second component, polypropylene was extruded from the extruder at an extrusion temperature of 250"C, and polyethylene terephthalate was extruded at an extrusion temperature of 280"C.

The first and second components were extruded according to their combination ratio so that the total amount was 2200 cc/min. (For example, if the combination ratio A/B of the first component (A) to the second component (B) was in a volume ratio of 50/50, the amount of the extruded first component was 1100 cc/min., and that of the extruded second component was 1100 cc/min) The components were melt spun by using a parallel type, sheath-core type, or eccentric sheath-core type spinneret as shown in the column of combination manner in Table 1.

The spinneret that holds 550 by 5 columns of round spinning pores, having a pore size of 0.35 mm, in the longitudinal direction of the spinneret was used. A group of filaments discharged from this spinneret was introduced into an air sucker, and drawn to obtain a group of drawn filaments. Then, the group of the filaments discharged from the air sucker was charged with a corona discharge apparatus, and passed between a pair of vibrating blade-like members to be distributed.

The group of the distributed filaments was collected as a filament fleece on an endless conveyor with a suction apparatus provided on its back surface. The drawing speed of the air sucker was suitably adjusted according to the types of the filaments so that the fineness of the filament was 2.2 d/f. The concentration of the inorganic substance powder in the filament was as shown in Table 1. The collected filament fleece was carried on the endless conveyor, and introduced between the pressed rolls of a point bond machine comprising heated embossing and smooth rolls, where the first component of the introduced filament fleece melted or softened in the area corresponding to the convex portion of the embossing roll so that the filaments thermally melted and adhered to each other to obtain a filament nonwoven fabric. The travelling speed of the endless conveyor was adjusted around a standard of 50 m/min. according to the types of the filaments so as to keep the basis weight of the filament nonwoven fabric being 28 g/m2. The peripheral velocity of the embossing roll was equal to the travelling speed of the endless conveyor. The linear load between the rolls and the roll temperature were suitably set so as to keep the average value of the bending resistances of the filament nonwoven fabric in the vertical and horizontal directions being around 35 mm.

While the nonwoven fabrics were all manufactured by a point bond method in the Examples, other methods such as a hot air heating method, a high pressure water stream method, a needle punching method, and an ultrasonic heating method may be used. Also, these methods may be combined.

When using polyethylene terephthalate as the second component, its [ n ] (limiting viscosity) value was 0.64. The [ n ] value was measured with a solvent of a mixture of phenol and ethane tetrachloride of the same weight at 20"C For the weight average particle sizes of the inorganic substance <BR> <BR> <BR> <BR> <BR> powders shown in Table 1, silica was 0.04,u m, TiO2 was 0.20 L m, alum was 0.95 u m, CaCO3 was 0.08 ,u m, CaO was 0.35,u m, MgO was 0.17 u and talc was 0.40 u m. Also, a rutile type titanium dioxide was used as TiO2 In Table 1, LDPE of the mixed polymer of the first component means low density polyethylene as described above, PP of the second component means polypropylene, and PET means polyethylene terephthalate. In the volume ratio A/B in the column of the combination ratio, A indicates the value of the first component, B indicates the value of the second component, and the value of the entire conjugated filament is 100.

The evaluation results of the thus obtained filament nonwoven fabrics are shown in Table 2.

(1) The filament nonwoven fabric obtained in Example 1 was used as the front cover 2 of a disposable diaper. In order to provide liquid permeability, a hydrophilic oil comprising 50 % of polyethylene glycol dimethyl laurate (molecular weight: 400) and 50 % of polyethylene glycol monolaurate (molecular weight: 500) was applied to the nonwoven fabric in an amount of 0.5 wt. %. The front cover was heat sealed to the back sheet comprising a film made of straight-chain low density polyethylene and the tissue paper wrapping the liquid absorbent layer. The thus obtained disposable diaper was tested for wear. As a result, a good absorbent article that provides good feeling and does not cause liquid leakage or displacement of the liquid absorbent layer was obtained.

The above disposable diaper comprises the above front cover, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, side sheets of a filament nonwoven fabric made of polypropylene, a round sheet of a filament nonwoven fabric made of polypropylene, and a back sheet of a film made of straight-chain low density polyethylene.

(2) The filament nonwoven fabric obtained in Example 2 was used as the side sheets of a disposable diaper. The side sheets were heat sealed to the front cover of a staple fiber nonwoven fabric made of polypropylene and the round sheet of a filament nonwoven fabric made of polypropylene. The thus obtained disposable diaper was tested for wear. As a result, a good absorbent article that provides good feeling and does not cause liquid leakage was obtained.

The above disposable diaper comprises a front cover of a staple fiber nonwoven fabric made of polypropylene, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, the above side gathers, a round sheet of a filament nonwoven fabric made of polypropylene, and a back sheet of a film made of straight-chain low density polyethylene.

(3) The filament nonwoven fabric obtained in Example 3 was used as the round sheet of a disposable diaper. The round sheet was heat sealed to the front cover of a staple fiber nonwoven fabric made of polypropylene. The thus obtained disposable diaper was tested for wear. As a result, a good absorbent article that provides good feeling and does not cause liquid leakage was obtained.

The above disposable diaper comprises a front cover of a staple fiber nonwoven fabric made of polypropylene, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, side sheets of a filament nonwoven fabric made of polypropylene, the above round sheet, and a back sheet of a film made of straight-chain low density polyethylene.

(4) The filament nonwoven fabric obtained in Example 4 was used as the back sheet laminate of a disposable diaper. The back sheet laminate was heat sealed to the film made of straight-chain low density polyethylene. The thus obtained disposable diaper was tested for wear.

As a result, an absorbent article that provides good feeling and good appearance was obtained.

The above disposable diaper comprises the front cover of the staple fiber nonwoven fabric made of polypropylene, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, side sheets of a filament nonwoven fabric made of polypropylene, a round sheet of a filament nonwoven fabric made of polypropylene, a back sheet of a film made of straight-chain low density polyethylene, and the above back sheet laminate.

(5) The filament nonwoven fabric obtained in Example 5 was used as the waist gathers of a disposable diaper. The waist gathers were heat sealed to the round sheet of a filament nonwoven fabric made of polypropylene. The thus obtained disposable diaper was tested for wear. As a result, a good absorbent article that provides good feeling and does not cause liquid leakage was obtained.

The above disposable diaper comprises a front cover of a staple fiber nonwoven fabric made of polypropylene, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, side sheets of a filament nonwoven fabric made of polypropylene, a round sheet of a filament nonwoven fabric made of polypropylene, a back sheet of a film made of straight-chain low density polyethylene, and the above waist gathers.

(6) The filament nonwoven fabrics obtained in Examples 6 and 7 were used as part of the liquid absorbent layer of a disposable diaper.

In the liquid absorbent layer, the filament nonwoven fabric of the present invention was inserted between the liquid absorbent layers 1 and 1' comprising a fluff pulp and a highly absorbent polymer, and heat sealed. The thus obtained disposable diaper was tested for wear. As a result, a good absorbent article that does not cause breakage of the liquid absorption layer or liquid leakage was obtained.

The above disposable diaper comprises a front cover of a staple fiber nonwoven fabric made of polypropylene, the above liquid absorbent layers, side sheets of a filament nonwoven fabric made of polypropylene, a round sheet of a filament nonwoven fabric made of polypropylene, a back sheet of a film made of straight-chain low density polyethylene.

(7) The filament nonwoven fabric obtained in Example 8 was used as the front cover 2 of a sanitary napkin. In order to provide liquid permeability, a hydrophilic oil comprising 50 % of polyethylene glycol dimethyl laurate (molecular weight: 400) and 50 % of polyethylene glycol monolaurate (molecular weight: 500) was applied to the nonwoven fabric in an amount of 0.5 wt. %. The front cover was heat sealed to the back sheet of a film made of straight-chain low density polyethylene and the tissue paper wrapping the liquid absorbent layer. The thus obtained sanitary napkin was tested for wear. As a result, a good absorbent article that provides good feeling and does not cause liquid leakage or the displacement of the liquid absorbent layer was obtained.

The above sanitary napkin comprises the above front cover, a liquid absorbent layer a fluff pulp and a highly absorbent polymer wrapped in tissue paper, side sheets of a filament nonwoven fabric made of polypropylene, and a back sheet of a film made of straight- chain low density polyethylene.

(8) The filament nonwoven fabric obtained in Example 9 was used as the side sheets of a sanitary napkin. The side sheets are heat sealed to the front cover of the staple fiber nonwoven fabric made of polypropylene. The thus obtained sanitary napkin was tested for wear.

As a result, a good absorbent article that provides good feeling and does not cause liquid leakage was obtained.

The above sanitary napkin comprises a front cover of a staple fiber nonwoven fabric made of polypropylene, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, the above side sheets, and a back sheet of a film made of straight-chain low density polyethylene.

(9) The filament nonwoven fabric obtained in Example 10 was used as the back sheet laminate of a sanitary napkin. The back sheet laminate was heat sealed to the film made of straight-chain low density polyethylene. The thus obtained sanitary napkin was tested for wear.

As a result, an absorbent article that provides good feeling and good appearance was obtained.

The above disposable diaper comprises the front cover of the staple fiber nonwoven fabric made of polypropylene, a liquid absorbent layer comprising a fluff pulp and a highly absorbent polymer wrapped in tissue paper, a side sheet of filament nonwoven fabric made of polypropylene, a back sheet of the film made of straight-chain low density polyethylene, and the above back sheet laminate.

(10) The filament nonwoven fabric obtained in Example 11 was used as part of the liquid absorbent layer of a sanitary napkin. In the liquid absorbent layer, the filament nonwoven fabric of the present invention was inserted between the liquid absorbent layers 1 and 1' comprising a fluff pulp and a highly absorbent polymer as shown in Fig.

4, and heat sealed. The outside of the obtained liquid absorbent layers were wrapped in tissue paper. The thus obtained sanitary napkin was tested for wear. As a result, a good absorbent article that does not cause the breakage of the liquid absorbent layers or liquid leakage was obtained.

The above sanitary napkin comprises a front cover of a staple fiber nonwoven fabric made of polypropylene, the above liquid absorbent layers, side sheets of a filament nonwoven fabric made of polypropylene, and a back sheet of a film made of straight-chain low density polyethylene.

The measurement method and evaluation standard of each evaluation item will be described below.

(Tensile strength) According to JIS L 1096, a tensile test by Tension tensile tester was performed to measure the tensile force in the vertical and horizontal directions. This tensile force was divided by the basis weight and the width of the sample to obtain the tensile strength in the vertical and horizontal directions. This was substituted in the formula (the tensile strength in the vertical direction x the tensile strength in the horizontal direction) x 1/2 to calculate the tensile strength. Here, the vertical direction refers to a machine direction in which the filament is carried on the endless conveyor, and the horizontal direction refers to the direction perpendicular to the machine direction. The unit is expressed by kg/cm(g/m2). (g/m2) means the value is calculated per the unit basis weight of the nonwoven fabric.

(Uniformity index of filament nonwoven fabrics) Five samples, each 5 cm by 5 cm, were taken from a nonwoven fabric in the horizontal direction at equal intervals. Each sample was cut into pieces 1 cm by 1 cm to be weighed. For each of the five samples, ((the maximum) - (the minimum)) X 100/(the average value) was calculated to find the average value of these. The value was used as the scale for distributing unevenness and unevenness in the filament fineness. As the value was smaller, the uniformity was higher. If the value was 80 or less, the uniformity was good.

(Feeling) Ten monitors performed sensory analysis by touching the surface of the filament nonwoven fabric by hand, and they each added one point if they felt the touch feeling was good.

(Spinning performance) Melt spinning was performed for three hours, and the number of occurrence of filament breakage was measured. If the number of occurrence of filament breakage was three or less, the spinning performance was good.

(Heat seal property (peeling strength)) The sample (the filament nonwoven fabric) obtained in each Example and Comparative Example and a polypropylene filament nonwoven fabric (the basis weight: 20g/m2) were cut into pieces 10 cm by 2.5 cm. These samples were overlapped so that their four corners align. An elongated heat seal was applied in the direction of the short side of the overlapped samples, that is, the width direction. The position where the heat seal was applied was 1 to 2 cm inside of one short side of the overlapped samples in the longitudinal direction. In other words, a space portion having a width of 1 cm without a heat seal was provided in parallel to one short side of the samples, and a heat seal having a width of 1 cm was applied adjacent to the space portion and in parallel to the short side. The heat seal was applied under the condition of a temperature of 1200C (for both upper and lower portions), 3 kg/cm2, and 3 seconds, using "HEAT SEAL TESTER TP-701" (made by TESTER SANGYO) as the heat seal apparatus.

The sample for a tensile test obtained by the above operation was opened from the other short side, the side where the heat seal was not applied, and each end was fixed to the chuck of a Tensilon tensile tester ("RDM-100" made by ORIENTEC) set at a 10 cm interval so as not to twist. The peeling strength was measured at a tensile speed of 100 mm/min., and the method for calculating the peeling strength conformed to JIS L 1086 (1983).

Table 1 First Component Inorganic substance **** Combi- Combi- (A) nation nation ratio manner * Mixed Volume ** *** poly- Com- Amount Parti- ratio mer ponent cle size Unit Wt. Wt. Weight µm m A/B % % ppm Example 1 20 30 LDPE Silica 1000 0.04 PP 50/50 ***** Example 2 20 30 LDPE TiO 10000 0.20 PP 40/60 ***** Example 3 20 30 LDPE Alum 15000 0.95 PP 40/60 ***** Example 4 20 30 LDPE CaCO, 35000 0.08 PP 50/50 ****** Example 5 20 30 LDPE CaO 500 0.35 PP 50/50 ******* Example 6 20 30 LDPE MgO 8000 0.17 PP 50/50 ****** Example 7 20 30 LDPE Talc 5000 0.40 PP 50/50 ****** Example 8 20 30 LDPE TiO 5000 0.20 PP 60/40 ******* Example 9 20 30 LDPE TiO2 5000 0.20 PET 50/50 Example 10 28 10 LDPE Silica 1000 0.04 PP 60/40 ****** Example 11 28 10 LDPE Silica 1000 0.04 PP 60/40 ****** Comparative 28 30 LDPE - - PP 50/50 k**** Example 1 Comparative 28 30 LDPE TiO2 100 0.20 PP 50/50 ****** Example 2 Comparative 80 30 LDPE TiO2 70000 0.20 PP 50/50 ****** Example 3 *Ethylene-vinyl acetate binary copolymer **Proportion of vinyl acetate ***Percentage content ****Second component (B) polymer *****Eccentric sheath-core type ******Parallel type *******Sheath-core type Note: The ethylene-vinyl acetate copolymer of Example 11 is saponified. The saponification degree is 80 %. The proportion of vinyl acetate includes the saponified portion.

Table 2 Spinning Nonwoven fabric ** performance Tensile Nonuniformity Feeling strength index Unit Number k /cm /m Point k /2.5cm Example 1 0 0.030 75 8 0.35 Example 2 1 0.029 74 9 0.30 Example 3 0 0.028 80 9 0.31 Example 4 0 0.028 69 10 0.41 Example 5 0 0.030 65 10 0.45 Example 6 0 0.029 75 9 0.42 Example 7 1 0.029 71 8 0.44 Example 8 0 0.027 65 8 0.41 Example 9 0 0.027 68 9 0.41 Example 10 0 0.028 64 9 0.38 Example 11 0 0.28 64 10 0.35 Comparative 11 0.020 130 3 example 1 Comparative 8 0.020 120 3 example 2 Comparative 15 0.018 150 2 example 3 *The number of occurrence of filament breakage **Heat seal property against polypropylene filament nonwoven fabric Note: The ethylene-vinyl acetate copolymer of Example 11 is saponified. The saponification degree is 80 %. The proportion of vinyl acetate includes the saponified portion.