JP2009001930A - Nonwoven fabric for absorbent article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonwoven fabric that has an excellent touch and softness and improved liquid permeability and is useful as various kinds of members of absorbent articles including a surface material. <P>SOLUTION: The nonwoven fabric for absorbent articles includes a fiber layer. A part or all of the constituent fibers of the fiber layer is a polyacetal fiber formed of a polymer having an oxymethylene structural unit. The polymer is preferably a copolymer of the oxymethylene structural unit and a structural unit formed of a component copolymerizable with the oxymethylene structural unit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-woven fabric for absorbent articles that is suitably used for absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads.

  In general, absorbent articles such as diapers and napkins are composed of an absorber that absorbs body fluids such as urine blood and liquid, a surface material that covers the absorber and contacts the skin, and a back surface that covers the back surface of the absorber and prevents liquid leakage. It consists of materials. The surface material of the absorbent article is required to be liquid permeable in order to quickly transfer body fluids such as blood and urine to the absorbent body. The liquid return prevention property etc. which are not returned to the top are requested | required.

Conventionally, non-woven fiber sheets mainly composed of polyolefin fibers have been used as the surface material of absorbent articles (see, for example, Patent Document 1). Polyolefin fibers are excellent not only in soft properties required for surface materials but also in moldability, processability, etc., and have a good balance of various properties as a material for forming surface materials.
However, in recent years, there has been a demand for further improvement in the softness of the surface material per skin, and there have been cases where polyolefin fibers cannot sufficiently meet this demand. As a method of increasing the softness of the surface material per skin, there is a method in which the skin contact surface (surface that contacts the skin) side of the surface material is composed of fibers thinner than conventional polyolefin fibers and the structure is densified. Such a method has a problem in terms of liquid absorbability because the gap between fibers of the constituent fibers of the surface material is narrowed, and the liquid permeability tends to decrease and the liquid tends to remain.

As another method of increasing the softness per skin of the surface material, 1) a method of reducing the basis weight of the surface material to lower the fiber assembly density, or 2) made of polyethylene terephthalate (PET) resin having a large specific gravity and high rigidity. There is a method using fiber.
However, since the method 1) may cause a decrease in workability and productivity due to a reduction in basis weight, it is difficult to reduce the basis weight to an extent effective for improving the softness per skin. It is not effective as a method of increasing the softness of the material per skin.
Further, the PET resin used in the above method 2) has a high melting point and is difficult to be heat-sealed. Also, since it is harder and has a higher friction than the polyolefin resin, it is difficult to use as a main forming material for the surface material. As a method of taking advantage of the above-mentioned PET resin, there is also a method using a composite fiber of PET resin and polyolefin resin. Such a composite fiber has a fiber diameter that is important for pursuing softness per skin of a surface material. It is difficult to reduce the thickness of the skin and there is a limit to improving the softness per skin.

  Further, as a surface material that can increase the softness per skin, Patent Document 2 discloses that the skin contact surface side has a three-dimensional uneven shape, and the skin contact surface side and the non-skin contact surface side are between. Discloses a three-dimensional sheet material having a void structure. However, such a three-dimensional sheet material has a manufacturing limitation in terms of the configuration for making the above-described structure, and a problem remains in terms of versatility.

JP-A-6-70954 JP 2004-345357 A

  Accordingly, an object of the present invention is to provide a non-woven fabric that is soft to the touch, excellent in liquid permeability, and useful as various members of absorbent articles including surface materials.

The present invention provides a nonwoven fabric for absorbent articles comprising a fiber layer, wherein a part or all of the constituent fibers of the fiber layer is a polyacetal fiber containing a polymer having an oxymethylene structural unit. The above-mentioned purpose is achieved.
The present invention also provides a nonwoven fabric for absorbent articles comprising a fiber layer, wherein the fiber layer comprises a first layer mainly composed of polyacetal fibers containing a polymer having an oxymethylene structural unit, and the first layer on the first layer. And a second layer mainly composed of fibers having a lower elongation recovery rate than the polyacetal fiber, and a concavo-convex shape is formed on the surface of the second layer. The above object is achieved by providing a non-woven fabric.

Moreover, this invention is the surface material of the absorbent article which covers the absorber which absorbs a bodily fluid, Comprising: The said objective is achieved by providing the surface material of the absorbent article which consists of the said nonwoven fabric.
Moreover, this invention is an exterior material of the absorbent article which covers the non-skin contact surface side of the absorptive main body which comprises the absorber which absorbs a bodily fluid, Comprising: It provides the exterior material of the absorbent article which consists of the said nonwoven fabric The above-mentioned purpose is achieved.

The nonwoven fabric for absorbent articles of the present invention has a good touch and is soft, has excellent liquid permeability, and is useful as various members of absorbent articles including surface materials.
Further, the surface material of the absorbent article of the present invention is soft and soft to the touch, excellent in liquid permeability, liquid remaining (a phenomenon that remains on the surface without liquid permeation) and liquid return (once absorbed by the absorber) The phenomenon that the liquid returns to the skin contact surface side) can be effectively suppressed.
Further, the exterior material of the absorbent article of the present invention is good in terms of touch, strength, wear resistance, heat sealability and the like.

Hereinafter, the nonwoven fabric for absorbent articles of this invention is demonstrated first.
The nonwoven fabric of the present invention is a polyacetal fiber comprising a fiber layer, and part or all of the constituent fibers of the fiber layer includes a polymer (oxymethylene polymer) having an oxymethylene structural unit (—OCH ₂ —). .

Oxymethylene polymer (polyacetal) has an amorphous part and a crystalline part, so it has excellent strength, elastic modulus, impact resistance, sliding characteristics, etc. Used for engineering plastics. The polyacetal fiber comprised including the oxymethylene polymer which has such a characteristic has the following features (a) to (f).
(A) Since the density is high and the strength is equal to or higher than that of polyester fibers and polypropylene fibers that are widely used as constituent fibers of this type of nonwoven fabric, when used as constituent fibers of the nonwoven fabric, it is bulky. Thus, the inter-fiber voids (openings) of the constituent fibers can be formed large. Nonwoven fabrics having large interfiber spaces have high liquid permeability and are suitable as surface materials for absorbent articles.
(B) Since the friction property is low (the fiber surface is smooth and slippery), when used as a constituent fiber of a nonwoven fabric, a skin-friendly nonwoven fabric is obtained.
(C) Since polyacetal has a relatively high official moisture content (higher than polyolefin), it is easy to perform hydrophilization treatment and has effects such as improving the durability of hydrophilicity. (D) Polyacetal has a solubility parameter (SP value). ) Is relatively high and is more compatible with water than polyolefins and polyesters. For this reason, when it is used as a synthetic fiber, it is easy to perform a hydrophilization treatment as in the case of (C), and the effect of improving hydrophilic durability and stability over time is obtained.
(E) Polyacetal has a relatively low melting point (equivalent to polypropylene and lower than polyethylene terephthalate), and is easy to process such as heat sealing and heat sealing, so it is easy to use as a surface material or exterior material for absorbent articles. .
(F) Since the stretch recovery property is good, it is difficult to be distorted, and when used as a constituent fiber of a nonwoven fabric, it is difficult to cause wrinkles and twist.

As the oxymethylene polymer, a homopolymer obtained by polymerizing only formaldehyde can be used. However, in consideration of spinnability, spinnability, stretchability, etc., the oxymethylene structural unit (—OCH ₂ —) and the oxymethylene structure are used. It is preferable to use a copolymer (oxymethylene copolymer) with a structural unit comprising a component copolymerizable to the unit.

The oxymethylene copolymer used in the present invention contains an oxymethylene structural unit as a main repeating unit and includes other repeating units (other structural units) made of a comonomer component copolymerizable therewith. In the present invention, an oxymethylene copolymer containing an oxyalkylene structural unit represented by the general formula (1): — [— (CR ₁ R ₂ ) _n —O—] _m — is used as the other structural unit. It is preferable. In the above formula, R _1, R ₂ is hydrogen, an alkyl group having 1 to 8 carbon atoms, an organic group, a phenyl group having an alkyl group of 1 to 8 carbon atoms, selected from an organic group having a phenyl group, R ₁ , R ₂ may be the same or different. m shows the integer of 2-6.

As the oxymethylene copolymer used in the present invention, the oxymethylene structural unit (—OCH ₂ —) is preferably 85 to 99 mol%, more preferably 90 to 98 mol%, based on the total structural unit of the polymer. Furthermore, the oxyalkylene structural unit represented by the general formula (1) is preferably contained in an amount of 1 to 15 mol%, more preferably 2 to 10 mol%, based on all structural units. When the introduction ratio of the oxyalkylene structural unit is too small, the crystallization rate of the oxymethylene copolymer is increased, the occurrence of yarn breakage during spinning is increased, and the stretchability may be lowered. An excessive amount of oxyalkylene structural units to be introduced is not preferable because the crystallization rate is lowered and high strength fibers cannot be obtained.

  The production method of the oxymethylene copolymer used in the present invention is not particularly limited, but generally a method of bulk polymerization of trioxane and a cyclic ether compound, which is a comonomer, mainly using a cationic polymerization catalyst is used. Is done. As the polymerization apparatus, any known apparatus such as a batch system and a continuous system can be used. Cyclic ether compounds used as comonomers include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis (chloromethyl) oxetane, tetrahydrofuran, trioxepane, 1,3 -Dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, among which ethylene oxide, 1,3 -Dioxolane, diethylene glycol formal and 1,4-butanediol formal are preferred. The amount of these cyclic ether compounds to be used is appropriately adjusted in consideration of the introduction ratio of the preferred oxyalkylene structural units described above. Post-treatment and stabilization of the oxymethylene copolymer obtained by polymerization, such as deactivation of the catalyst, removal of unreacted monomers, washing of the polymer, drying, stabilization of unstable ends, and various other stability What is necessary is just to perform the stabilization process by the mixing | blending of an agent by a well-known method.

  The oxymethylene polymer used in the present invention (including an oxymethylene copolymer, hereinafter the same unless otherwise specified) has a melt index (MI) of preferably 2.5 to 90 g / 10 min. More preferably, it is 5-80 g / 10min. MI is a value measured under a load of 190 ° C. and 2160 g in accordance with ASTM D-1238. An oxymethylene polymer having MI in such a range can provide industrially stable fibers by melt spinning or the like. MI can be adjusted with the addition amount of the chain transfer agent (for example, methylal etc.) used at the time of superposition | polymerization.

The polyacetal fiber used in the present invention may be composed only of the above-described oxymethylene polymer as a resin component, or contains an oxymethylene polymer and one or more other resins other than the oxymethylene polymer. It may be configured as. The content of the oxymethylene polymer in the polyacetal fiber is preferably 30 to 100% by weight, more preferably 40 to 70% by weight, based on the fiber weight.
The fiber layer may contain only polyacetal fibers composed only of oxymethylene polymers as polyacetal fibers, or only polyacetal fibers containing oxymethylene polymers and other resins. It may be included, or both of these fibers may be included.

  As said other resin used together with an oxymethylene polymer, thermoplastic elastomers, such as rubber | gum, a polyolefin-type elastomer, a polyester-type elastomer, a polyurethane-type elastomer, etc. can be used, for example. Further, a resin other than the thermoplastic elastomer, for example, a thermoplastic resin such as polyethylene (PE), polypropylene (PP), polyester, and polyamide can be used. These can also be used in combination of two or more.

When the polyacetal fiber used in the present invention contains another resin in addition to the oxymethylene polymer as described above, the fiber form of the polyacetal fiber (resin-containing form) includes the oxymethylene polymer and other resins. Examples thereof include a single fiber made of a blend polymer with a resin, or a composite fiber containing an oxymethylene polymer and another resin without being mixed. The composite fiber here is a fiber obtained by compounding two or more kinds of resins having different components with a spinneret and simultaneously spinning them, and a plurality of components are each continuous in the length direction of the fiber in a single fiber. Those that are bonded together. Examples of the composite fiber include a parallel type composite fiber and a core-sheath type composite fiber.
In the fiber layer, as a polyacetal fiber containing an oxymethylene polymer and another resin, only the single fiber may be included, or only the composite fiber may be included, Or these both fibers may be contained.

  In the present invention, as the polyacetal fiber, it is easy to form the nonwoven fabric, the bulkiness of the nonwoven fabric, and the heat resistance against heat sealing by using a polyacetal fiber in the form of the composite fiber (hereinafter also referred to as a composite polyacetal fiber). From the viewpoint of sex. Examples of the fiber form of the composite polyacetal fiber used in the present invention include a parallel type (side-by-side type) and a sheath-core type (sheath-core type). The sheath core type includes a concentric circle type and an eccentric type. These composite fibers can be produced by a known spinning method. In the present invention, in particular, a sheath-core type composite polyacetal fiber is preferable in that the above-described effects can be reliably achieved.

  In the composite polyacetal fiber, as the other resin used in combination with the oxymethylene polymer, a thermoplastic resin having a higher melting point than the oxymethylene polymer (a high melting point thermoplastic resin) is preferably used. That is, the composite fiber polyacetal fiber of the oxymethylene polymer and the high melting point thermoplastic resin has high strength mainly by the action of the oxymethylene polymer and has excellent heat resistance mainly by the action of the high melting point thermoplastic resin. Therefore, the nonwoven fabric using the composite polyacetal fiber is stable against heat seal fusion and high temperature sealing. In general, a high-melting point thermoplastic resin has high properties such as the strength and Young's modulus of the resin. Therefore, when a composite polyacetal fiber containing a high-melting point thermoplastic resin is used, the high-melting point thermoplastic resin Due to the synergistic effect of such characteristics and the strength and elasticity of the oxymethylene polymer, a bulky, excellent cushioning property, a large inter-fiber gap between constituent fibers and excellent liquid permeability can be obtained. Further, by using a composite polyacetal fiber containing a high melting point thermoplastic resin, there is an advantage that a nonwoven fabric having such excellent characteristics can be obtained without using a special resin or a production method.

  In the composite type fiber polyacetal fiber of the oxymethylene polymer and the high melting point thermoplastic resin, the difference in melting point between the oxymethylene polymer and the high melting point thermoplastic resin is preferably 30 ° C. or more, more preferably 60 to 110 ° C. is there. The melting point of the oxymethylene polymer is usually 160 to 180 ° C. Examples of such high melting point thermoplastic resins include polymethylpentene, polyamides such as nylon 6 and nylon 66; polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate; polyphenylene sulfides; polyether ether ketones, and the like. Polyester is particularly preferable. The content of the high melting point thermoplastic resin in the polyacetal fiber is preferably 30 to 70% by weight, more preferably 40 to 60% by weight.

  On the other hand, when the composite polyacetal fiber is used in the present invention, as the other resin used in combination with the oxymethylene polymer, a thermoplastic resin having a melting point lower than that of the oxymethylene polymer (low melting thermoplastic resin) can also be used. . The composite polyacetal fiber of oxymethylene polymer and low-melting point thermoplastic resin is a non-woven fabric although it is inferior in heat resistance and bulkiness compared to the above-mentioned composite type polyacetal fiber of oxymethylene polymer and high-melting point thermoplastic resin. Low temperature processing is possible in formation, which is preferable in terms of ease of production and bulkiness of the nonwoven fabric. The difference in melting point between the oxymethylene polymer and the low melting point thermoplastic resin is preferably 20 ° C. or higher, more preferably 30 to 60 ° C. Examples of such a low-melting point thermoplastic resin include polyethylene, a copolymer of ethylene and α-olefin, a copolymer of polypropylene and ethylene, and the like. Particularly, polyethylene has low temperature processability and strength. Is preferable.

When the composite type polyacetal fiber of oxymethylene polymer and high melting point thermoplastic resin is a sheath core type (eccentric type) composite fiber, the oxymethylene polymer is the sheath and the high melting point thermoplastic resin is the core Is preferred. The high-melting point thermoplastic resin constituting the sheath-core type composite fiber may be appropriately selected from the above-mentioned ones according to the use of the nonwoven fabric, and is not particularly limited. From the viewpoint, polyester is particularly preferable.
Further, when the composite polyacetal fiber of the oxymethylene polymer and the low-melting thermoplastic resin is a sheath-core (eccentric) composite fiber, the oxymethylene polymer is the core and the low-melting thermoplastic resin is the sheath. Preferably there is. The low-melting point thermoplastic resin constituting the sheath-core type composite fiber may be appropriately selected from the above-mentioned ones according to the use of the nonwoven fabric, and is not particularly limited. However, heat melting characteristics (low temperature melting), processability From the viewpoint of versatility and texture, polyethylene is particularly preferable.

The polyacetal fiber used in the present invention may be in any form of long fiber and short fiber. The long fiber means a fiber having a length of 100 mm or more, and includes continuous fibers. The short fiber means one having a length of less than 100 mm.
The average fineness of the polyacetal fiber used in the present invention is appropriately selected depending on the use of the nonwoven fabric and is not particularly limited, but is preferably 2 dtex or less, more preferably 0.1 to 1. 7 dtex. In particular, when the nonwoven fabric of the present invention is used as a surface material of an absorbent article, it is preferable that the average fineness of the polyacetal fiber is in the above range.

  In addition to the resin component such as oxymethylene polymer, the polyacetal fiber used in the present invention has various additives as necessary, for example, coloring agents such as dyes and pigments, lubricants, nucleating agents, releasing agents, and antistatic agents. One or more agents such as an agent, a surfactant, an organic polymer material, an inorganic or organic fibrous, plate-like, or granular filler may be added within a range that does not impair the object of the present invention. it can.

  Among these additives, in particular, the lubricant imparts low friction to the surface of the polyacetal fiber to make it smooth, and as a result, a non-woven fabric having a low touch on the skin and a good touch can be obtained. Preferably used. Examples of the lubricant include hydrocarbons such as liquid paraffin and polyethylene wax, and fatty acids such as stearic acid amide and oleic acid amide. The content of the lubricant is preferably 0.01 to 1.5% by weight, more preferably 0.1 to 0.5% by weight, based on the total weight of the resin component contained in the polyacetal fiber.

  The polyacetal fiber used in the present invention can be produced by a known spinning method. For example, a melt blown method in which a molten resin is extruded through a nozzle hole and the extruded molten resin is stretched with hot air to thin the fibers, or a semi-molten resin is stretched with cold air or a mechanical draw ratio. It can be manufactured by a bond method. Polyacetal fibers can also be produced by a spinning blow method, which is a type of melt spinning method.

  The fiber layer constituting the nonwoven fabric of the present invention may contain only the above-mentioned polyacetal fibers as constituent fibers (all of the constituent fibers are polyacetal fibers), or may contain polyacetal fibers and / or other fibers. Good (part of the constituent fibers are polyacetal fibers). 1 type, or 2 or more types can be used for another fiber.

  Examples of other fibers that can be included in the fiber layer according to the present invention include fibers made of one or more resins selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, and nylon; these resins. In the case of two or more resins, a single fiber or a composite fiber may be used. When the fiber layer is configured to include polyacetal fibers and other fibers, the content weight ratio between them is preferably (polyacetal fibers) :( other fibers) = 20: 80 to 90:10. . Further, when the fiber layer includes, as other fibers, fibers made of a resin having a melting point lower than that of polyacetal (low melting point resin fibers), the content weight ratio of the polyacetal fibers to the low melting point resin fibers is ( Polyacetal fiber): (low melting point resin fiber) = 30: 70 to 70:30 is particularly preferable from the viewpoint of the workability of the low temperature heat seal. Moreover, when the fiber layer contains a fiber that does not melt at the melting point of polyacetal as another fiber, the content weight ratio of the polyacetal fiber to the fiber is adjusted to 30:70 to 70:30, The advantage of improved heat resistance is obtained.

  The average fineness of the other fibers is preferably less than 12 dtex, more preferably 1 to 8 dtex, from the viewpoint of the processability of the nonwoven fabric, the touch, and the uniformity of the nonwoven fabric. Further, the other fibers may be in any form of long fibers and short fibers.

  The constituent fibers (polyacetal fiber, other fibers) of the fiber layer according to the present invention may be treated with a hydrophilic oil agent. When the constituent fibers are treated with a hydrophilic oil agent, the liquid absorption rate of the fiber layer is increased. In particular, when a nonwoven fabric (fiber layer) is used as a surface material of an absorbent article, or as a second sheet (sublayer sheet) disposed between the absorbent body and the surface material in the absorbent article. In this case, it is effective in terms of preventing leakage that the constituent fibers of the fiber layer are treated with a hydrophilic oil agent. Among the constituent fibers of the fiber layer, when the polyacetal fiber is treated with a hydrophilic oil agent, it is effective in terms of liquid absorption speed and prevention of leakage. Examples of hydrophilic oil agents include sulfate ester bases, C8-C30 alkyl phosphate ester bases, anionic surfactants including sulfonate groups, betaine activators, polyoxyethylene alkyl ethers, polyoxyethylene sorbitan monooleates, and sorbitans. Monooleate, polyoxyalkylene modified organosiloxane, blend of alkylolamide type compound and polyoxyalkylene modified organosiloxane, blend of polyglycerin fatty acid ester or polyoxyalkylene modified organosiloxane, polyether polyester block A polymer or a blend thereof and a polyoxyalkylene-modified organosiloxane, a surfactant having a hydrocarbon group having 28 or more carbon atoms as a hydrophobic group, and a polyoxyalkylene-modified organosiloxane It can be used a blend or the like. The fiber treatment with the hydrophilic oil agent is performed by, for example, immersing the fiber in an oil bath containing the hydrophilic oil agent, coating the hydrophilic oil agent with a kiss roll, spraying with a spray, etc. This can be done by squeezing.

  Moreover, the constituent fiber (polyacetal fiber, other fiber) of the fiber layer according to the present invention may be a crimped fiber having crimps. By using the crimped fibers, the effect of increasing the voids of the nonwoven fabric, improving the cushioning property against the load, making it difficult to be crushed, and improving the texture is obtained. In particular, it is effective that the polyacetal fiber is a crimped fiber. The ratio of the crimped fibers contained in the fiber layer is preferably 30 to 100% by weight, more preferably 50 to 100% by weight, based on all the constituent fibers of the fiber layer.

  In the present invention, the crimped fiber is a mechanically crimped fiber having a two-dimensional crimp, a three-dimensional crimped fiber having a three-dimensional crimp, or a three-dimensionally crimped coil by application of heat. A fiber to be crimped (latently crimped fiber) or the like can be used. In general, the size of the crimp in each of the mechanically crimped fiber and the three-dimensionally crimped fiber is larger than the size of the crimp when the latent crimped fiber comes to have crimps by application of heat. . Therefore, from the viewpoint of easily obtaining a bulky nonwoven fabric, it is preferable to use mechanical crimped fibers or three-dimensional crimped fibers as the crimped fibers, not latent crimped fibers.

In particular, as the polyacetal fiber, a parallel type or eccentric type composite fiber (composite type polyacetal fiber) that expresses a three-dimensional manifested crimp can make a larger fiber occupation volume, so that the voids of the nonwoven fabric, It is preferable in terms of cushioning properties. Here, the “composite polyacetal fiber expressing three-dimensional crimps” may be the above-mentioned three-dimensional crimp fiber having three-dimensional crimps from the beginning, and imparting heat. The latent crimped fiber may be crimped three-dimensionally for the first time, but the three-dimensional crimped fiber is preferable from the viewpoint of developing a larger three-dimensional crimp.
Such three-dimensional crimps are manifested by the physical properties, thermal properties, etc. of the resin, as well as by the composite shape of the fibers. In particular, the oxymethylene polymer has a resin property of high stretch recovery, so when forming a composite fiber with another resin, it is easy to express a three-dimensional crimp by performing a tension treatment. Synergistic effects with the properties provide high fiber recovery and elasticity, and show remarkable effects in the formation of voids in the nonwoven fabric, cushioning characteristics when subjected to a load, and recovery.

The nonwoven fabric of this invention is obtained by manufacturing the said fiber layer using a well-known nonwoven fabric manufacturing method.
The fiber layer according to the present invention may be (A) a form in which constituent fibers are fused together, or (B) a form in which constituent fibers are intertwined. What is necessary is just to select any form of (A) or (B) according to the use of a nonwoven fabric. The fiber layer in the form of (A) maintains the form of the fiber layer by the intersection of the constituent fibers being fused by the application of heat. The fiber layer in the form (B) maintains the form of the fiber layer by entanglement of the constituent fibers, and the intersection of the fibers is not fused.

  In the production process of the fiber layer in the form (A), the fiber web which is the precursor of the fiber layer (the object before becoming the fiber layer) is heated to fuse the constituent fibers of the fiber web. Is formed. When the fiber layer of the form (A) is used, the constituent fiber is a polyacetal in the form of a sheath-core type composite fiber in which the oxymethylene polymer is the core and the low-melting point thermoplastic resin (preferably polyethylene) is the sheath. The use of fibers is preferable in terms of ease of production and bulkiness of the nonwoven fabric because it can be processed at low temperatures in forming the nonwoven fabric. The fiber web is a spunbonding method in which fibers directly spun from a spinning nozzle are stretched by an ejector or the like and deposited on a conveyor belt, or a spinning method, a card method in which stretched staple fibers are formed using a card machine, spinning, and stretching. It can be formed by an airlaid method or the like in which fibers are short cut and the fibers are passed through a screen by air force and accumulated. Examples of means for heating the fiber web include a method of passing hot air (air-through method), a method of steam heating, a method of passing between heat rolls, and a method of radiant heat such as far infrared rays. In particular, the air-through method is suitable for producing a fiber layer (nonwoven fabric) that is bulky and has a large interfiber gap. Moreover, since the oxymethylene polymer which is the main component of the polyacetal fiber has a relatively high melting point, short-time heat treatment by steam heating is preferably used in the present invention. The fiber layer (nonwoven fabric) in the form of (A) is, among others, a fiber layer heated by a fiber web by the air-through method, because it is bulky, has a high void structure and high resilience (cushioning). It is particularly suitable for applications in which such characteristics are required as constituent members of absorbent articles, for example, surface materials, diffusion sheets (sublayer sheets), cushion materials, fastener materials, and the like.

  The fiber layer having the form (B) is formed by entanglement between the constituent fibers of the fiber web, which is a precursor of the fiber layer, in the manufacturing process. In the case of the fiber layer having the form (B), it is preferable to use a fiber having a single structure of an oxymethylene polymer as the constituent fiber from the viewpoint of low friction characteristics and texture. Use of polyacetal fibers in the form of split composite fibers composed of coalescence and the above-mentioned low-melting thermoplastic resin (preferably polyethylene) increases the strength of the nonwoven fabric, lower friction characteristics, improved texture / feel, low temperature sealing process This is preferable. The fiber web can be formed in the same manner as in the above (A). A known water knee drink method (hydroentanglement method) may be used as the means for intertwining the fiber web. The fiber layer (nonwoven fabric) in the form of (B) is particularly rich in flexibility and softness, and uses where such characteristics are required as a constituent member of an absorbent article, for example, a surface material or an exterior material, It is particularly suitable for individual packaging materials.

The basis weight of the fiber layer constituting the nonwoven fabric of the present invention is preferably 25 g / m ² or less, still more preferably 10~18g / m ^2. When the nonwoven fabric of this invention consists of a laminated body of two or more fiber layers, it is preferable that the basic weight of each fiber layer exists in the said range.
In particular, in the present invention, it is preferable that the average fineness of the polyacetal fibers constituting the fiber layer is 2 dtex or less as described above, and the basis weight of the fiber layer is 25 g / m ² or less. By satisfying these conditions, the nonwoven fabric becomes bulky and the inter-fiber voids become large, so that better liquid permeability and texture can be obtained, and it is particularly suitable as a surface material for absorbent articles.

The thickness of the fiber layer according to the present invention is preferably 0.3 to 4 mm, more preferably 0.5 to 3 mm. When the nonwoven fabric of this invention consists of a laminated body of two or more fiber layers, it is preferable that the thickness of each fiber layer exists in the said range. The thickness is measured by either the following method 1 or method 2 after leaving the fiber layer in an environment of 20 ± 2 ° C. and 65 ± 2% RH for 2 days or more with no load.
Method 1: A fiber layer (measurement sample) is sandwiched between flat plates with a load of 0.5 cN / cm ² . Under the state, the cross section of the fiber layer is observed with a microscope at a magnification of 50 to 200 times, and the average thickness is obtained for each field of view. Let the average value of the thickness of 3 visual fields be the thickness of a fiber layer.
Method 2: A laser displacement meter sensor is fixed on a surface plate so that displacement can be measured in the vertical direction. Next, a white and smooth plate-like material that is not easily deformed is prepared, cut into a size such that the measurement pressure becomes a load of 0.5 cN / cm ² , and used as a measurement load plate. Place the measurement load plate on the surface plate and calibrate and set the displacement sensor so that it becomes 0 when the laser spot of the displacement sensor is applied to the load plate. A fiber layer (measurement sample) is placed on the surface plate in the vicinity of the portion where the laser spot hits, and then a measurement load plate is gently placed on the fiber layer hit by the laser spot, and the amount of displacement is read. This is repeated three times, and the average value is taken as the thickness of the fiber layer.

  The nonwoven fabric of the present invention may have a single-layer structure composed of only one fiber layer or a multilayer structure composed of a laminate of two or more fiber layers. In the latter case, a laminate of fiber layers having the same composition and physical properties may be used, or a laminate of two or more types of fiber layers having different compositions and physical properties may be used. These forms are appropriately selected according to the use of the nonwoven fabric.

As a preferable form in case the nonwoven fabric of this invention consists of a laminated body of two or more fiber layers, the following are mentioned, for example.
That is, a non-woven fabric for absorbent articles comprising a fiber layer, wherein the fiber layer is laminated on the first layer and partially with the first layer. A second layer mainly composed of fibers bonded and having a lower recovery rate than the polyacetal fiber, and the surface of the second layer (the surface opposite to the surface facing the first layer) has an uneven shape. It is the formed nonwoven fabric (uneven nonwoven fabric). This uneven nonwoven fabric has an uneven shape formed on the surface of the second layer that functions as a skin contact surface, so that the surface contact area with the skin is low, and has excellent cushioning properties due to the unevenness. Therefore, it is gentle to the skin and is suitable as a surface material for absorbent articles. In addition, the uneven nonwoven fabric is also excellent in the effect of reducing liquid residue and liquid return, and can prevent skin roughness and further keep the skin.

The content of polyacetal fiber in the first layer is preferably 70% by weight or more, more preferably 100% by weight.
As the fiber used in the second layer, which has a lower elongation recovery rate than the polyacetal fiber (low elongation recovery rate fiber), a fiber having an elongation recovery rate of 70% or less at 20% elongation is preferably used. The elongation recovery rate at 20% elongation of the polyacetal fiber is usually 70 to 85%. Specific examples of low elongation recovery rate fibers include fibers made of polyester, polypropylene, and polyethylene resins, copolymer fibers thereof, and composite fibers made of combinations of these resins. Species or two or more can be used. The content of the low elongation recovery rate fiber in the second layer is preferably 60% by weight or more, and more preferably 100% by weight.

The basis weight of the first layer, from the viewpoint of elongation recovery expression, preferably 5 to 50 g / m ^2, more preferably a 7~25g / m ^2.
The basis weight of the second layer, skin, cushioning property, in view of the liquid return, preferably 5 to 40 g / m ^2, more preferably a 7~25g / m ^2.

  The uneven nonwoven fabric is formed by laminating a first layer precursor mainly composed of the polyacetal fiber and a second layer precursor mainly composed of a fiber having a lower elongation recovery rate than the polyacetal fiber, and a portion between these precursors is partially laminated. It is obtained by removing the tensile load after applying a tensile load to the laminated sheet bonded to the substrate and extending the laminated sheet in the plane direction. That is, the uneven shape on the surface of the second layer described above is formed by utilizing the difference in elongation recovery rate between the first layer precursor and the second layer precursor (the first layer has a higher elongation recovery rate). Has been. After applying the tensile load to the laminated sheet and extending the laminated sheet in the plane direction, when the tensile load is removed, the first layer precursor having a relatively high elongation recovery rate is almost free from wrinkles and irregularities. The second layer precursor, which does not occur and recovers to the same state as before stretching, has a relatively low elongation recovery rate, but the distortion caused by stretching is not completely removed, and an uneven shape is formed on the surface. It is done.

The first layer precursor and the second layer precursor can be respectively produced by the same method as the method for producing the fiber layer of (A) or (B) described above.
As a means for partially joining the first layer precursor and the second layer precursor to form the laminated sheet, various joining means such as heat embossing, ultrasonic embossing, and adhesion with an adhesive can be used. . In addition, the shape of the joint portion in the laminated sheet may be a circle, an ellipse, a triangle, a rectangle, a diamond, a heart shape, or a combination thereof, or a continuous shape, for example, a linear shape such as a straight line or a curve, or a lattice shape. it can. Further, the tensile load applied to the laminated sheet is adjusted so that the laminated sheet is stretched by 20% in the plane direction.

  The nonwoven fabric of the present invention is suitable as a constituent member of an absorbent article, for example, a surface material (surface sheet) of an absorbent article such as a sanitary napkin or a disposable diaper, and between the absorbent body and the surface material in the absorbent article. It is suitably used as a second sheet (sub-layer sheet) disposed on the outer surface, an exterior material covering the non-skin contact surface side of the absorber, and the like. Since the nonwoven fabric of the present invention is configured to include the polyacetal fibers having the above-described features (a) to (f), for example, when used as a surface material of an absorbent article, the touch is good and soft, It is bulky, hardly wrinkles or twists, has excellent liquid permeability, and can effectively reduce liquid residue and liquid return. When used as an exterior material for absorbent articles, good results are obtained in terms of touch, strength, wear resistance, heat sealability, and the like.

The nonwoven fabric of the present invention preferably comprises at least one of the following (1) to (9). There is no restriction | limiting in the combination of following (1)-(9). The details of the following (1) to (9) are as described above.
(1) The constituent fibers (polyacetal fiber, other fibers) of the fiber layer are treated with a hydrophilic oil.
(2) The constituent fibers (polyacetal fiber, other fibers) of the fiber layer are crimped fibers.
(3) The constituent fibers of the fiber layer are fused together (having the fiber layer in the form of (A)).
(4) The fiber layer is subjected to known embossing treatment such as heat embossing treatment.
(5) The constituent fibers of the fiber layer are entangled (having the fiber layer in the form of (B)).
(6) The polyacetal fiber contained in the fiber layer is a parallel or sheath-core (eccentric) composite fiber (composite-type polyacetal fiber) of an oxymethylene polymer and a resin other than the oxymethylene polymer. ) And three-dimensional manifested crimps.
(7) The polyacetal fiber contained in the fiber layer is composed of an oxymethylene polymer and a thermoplastic resin having a melting point higher than that of the polymer (high melting point thermoplastic resin).
(8) A lubricant is added to the constituent fibers (polyacetal fiber, other fibers) of the fiber layer.
(9) The average fineness of the fibers constituting the fiber layer is 2 dtex or less, and the basis weight is 25 g / m ² or less.

  In particular, when the nonwoven fabric of the present invention is used as a surface material of an absorbent article, the nonwoven fabric as the surface material preferably includes at least one of the above (1) to (4). It is more preferable that all of (4) to (4) are provided.

Moreover, when using the nonwoven fabric of this invention as a second sheet | seat of an absorbent article, it is preferable that this nonwoven fabric as a second sheet is equipped with at least any one of said (1), (6), (7). . In the nonwoven fabric of the present invention as the second sheet, particularly preferable combinations include, for example, the combinations of (1), (3), and (6); (1), (2), (3), (6), Combination of (7); Combinations of (1), (2), (4) and (6) are mentioned.
As described above, the second sheet is a sheet disposed between the absorbent body and the surface material in the absorbent article. The second sheet efficiently moves the liquid to the absorbent body, and the liquid once absorbed by the absorbent body. It plays a role of preventing so-called liquid return returning to the surface material side. The nonwoven fabric of this invention provided with the said combination can fully take such a role.

Moreover, when using the nonwoven fabric of this invention as an exterior material of an absorbent article, this nonwoven fabric as an exterior material is any one of said (3), (4), (5), (8), (9). It is preferable to have one. In the nonwoven fabric of the present invention as the exterior material, particularly preferable combinations include, for example, combinations of (3), (8), and (9); combinations of (4), (8), and (9). .
The exterior material is a sheet material that covers the non-skin contact surface side of the absorbent body together with the back surface material in the absorbent article, and the exterior material has air permeability, good feel when touched, wear resistance It is required to be excellent in heat resistance and to be heat-sealable. On the other hand, since the oxymethylene polymer has a smooth and smooth feel and is resistant to abrasion, the nonwoven fabric of the present invention using the oxymethylene polymer can satisfy the required characteristics as an exterior material. Especially, the nonwoven fabric of this invention provided with the said combination is suitable as an exterior material.

  Examples of the nonwoven fabric of the present invention suitable as the surface material include the following nonwoven fabrics A, B, and C.

Nonwoven fabric A: polyacetal fiber (fineness: 2 dtex, fiber length) consisting only of an oxymethylene polymer (including oxymethylene copolymer; the same shall apply hereinafter) treated with a hydrophilic oil and having a three-dimensional crimp (steric crimp) A non-woven fabric having a basis weight of 25 g / m ² obtained by forming a fiber web by the card method using only 51 mm) and subjecting the fiber web to a heat embossing treatment with an embossing rate of 20%.

Non-woven fabric B: A composite fiber (composite polyacetal fiber, fineness 2 dtex) of an oxymethylene polymer and PET (other resin) treated with a hydrophilic oil and having a three-dimensional crimp (steric crimp) , An oxymethylene polymer and PET (others) having a first layer (basis weight of 15 g / m ² ) consisting of only a fiber length of 51 mm, a two-dimensional crimp (mechanical crimp) treated with a hydrophilic oil agent And a second layer (basis weight 10 g / m ² ) consisting only of a sheath-core type composite fiber (composite type polyacetal fiber, fineness 1.9 dtex, fiber length 51 mm) and A two-layer air-through nonwoven fabric having a basis weight of 25 g / m ² , which is formed by fusing one layer and the second layer. The hydrophilic oil agent in the first layer is preferably less hydrophilic than the hydrophilic oil agent in the second layer.

Non-woven fabric C: first non-woven fabric C composed of only polyacetal fibers (fineness 1.5 dtex, fiber length 51 mm) made of oxymethylene polymer, treated with a hydrophilic oil and having two-dimensional crimps (mechanical crimps) And a second card web layer composed only of PP / PE composite fibers (parallel type composite fibers, fineness of 1.5 dtex, fiber length of 51 mm) treated with a hydrophilic oil on the card web layer. The laminate is subjected to heat embossing at an embossing rate of 16% with a dot area of 1.5 mm ² to obtain a preliminary nonwoven fabric having a basis weight of 27 g / m ² . A non-woven fabric that is shear-processed to the extent that the preliminary non-woven fabric is not destroyed by passing between male and female rolls. The nonwoven fabric C is an example of the uneven nonwoven fabric, and an uneven shape (a fine convex bulge) is formed on the surface of the second card web layer.

  The non-woven fabric A is bulky because the elasticity of the constituent fibers (polyacetal fibers) is high, and is smooth and gentle to the skin because the constituent fibers are low in friction equal to or higher than that of polyolefin. Moreover, since the oxymethylene polymer has good compatibility with the hydrophilic oil agent, when the non-woven fabric A is used as the surface material of the absorbent article, the surface material is repeatedly highly absorbent and hardly leaks.

  Nonwoven fabric B is bulky because of the high elasticity of the constituent fibers, and smooth and gentle to the skin because the oxymethylene polymer has a low friction equal to or higher than that of olefin. When the nonwoven fabric B is used as the surface material of the absorbent article, the gap between fibers is large, so the absorption time is short, and the oxymethylene polymer has good compatibility with the hydrophilic oil agent, and the hydrophilic level of the hydrophilic oil agent Since it is easy to control, it is easy to create a hydrophilic gradient between the first layer and the second layer, which makes it highly repetitive, excellent in suppressing liquid residue and liquid return, and further maintaining the skin, etc. Produce the effect.

  When the non-woven fabric C is used as a surface material so that the second card web layer is on the skin contact surface side, the second card web layer has a very soft tactile sensation and the convex structure enhances air permeability. Reduces skin stuffiness. Further, in the nonwoven fabric C, at a temperature that is equal to or higher than the melting point of PE used in the second card web layer and lower than the melting point of the oxymethylene polymer used in the first card web layer (for example, 132 ° C.), When heat-sealing treatment is performed with an air-through dryer, fluffing on the surface is suppressed, and the shape retention of the convex structure is further enhanced, so that cushioning can be further improved, thereby further improving liquid return. Can be suppressed.

  Examples of the nonwoven fabric of the present invention suitable as the second sheet include the following nonwoven fabric D.

  Non-woven fabric D: Only three-dimensional crimps (steric crimps) and parallel type composite fibers of oxymethylene polymer and PE (other resin) (composite type polyacetal fiber, fineness 4 dtex, fiber length 51 mm) An air-through nonwoven fabric obtained by forming a fiber web by the card method and heat-treating the fiber web with a dryer.

  Since the nonwoven fabric D is bulky, when it is used as a second sheet of an absorbent article, the nonwoven fabric D is excellent in absorbability such as loose stool and highly viscous menstrual blood / origin. Further, since the elasticity of the constituent fibers is high, the cushioning property is high, and when used for the second sheet, it is effective in preventing twisting and breaking. In particular, as another resin, for example, an elastomer resin such as a low density polyethylene having a density of 0.9 or less using a single site catalyst has a higher effect of preventing twisting and bending.

  Examples of the nonwoven fabric of the present invention suitable as an exterior material include the following nonwoven fabrics E, F, and G.

Non-woven fabric E: Polyacetal fiber (fineness: 1.5 dtex) made only of an oxymethylene polymer is melt-spun and directly deposited on a conveyor belt (ie, by a spunbond method) to form a fiber web, and the fiber web is embossed A nonwoven fabric having a basis weight of 15 g / m ² , which is subjected to heat embossing at a rate of 20%. In the nonwoven fabric E, the constituent fibers (polyacetal fibers) are not treated with an oil agent.

Nonwoven fabric F: Hydroentanglement treatment is applied to a card web layer composed only of polyacetal fibers (fineness 1.5 dtex, fiber length 51 mm) having only two-dimensional crimps (mechanical crimps) and consisting of oxymethylene polymers. A spunlace nonwoven fabric having a basis weight of 35 g / m ² , which is applied and dried.

Non-woven fabric G: A card web layer composed only of parallel type composite fibers (complex type polyacetal fiber, fineness 2 dtex, fiber length 51 mm) of oxymethylene polymer and PE (other resin) has a dot area of 1. Heat embossing is performed at an embossing rate of 20% at 5 mm ² to obtain a preliminary nonwoven fabric having a basis weight of 18 g / m ² , and the preliminary nonwoven fabric is passed between a pair of blade-groove male and female rolls so that the preliminary nonwoven fabric is not broken. Nonwoven fabric that has been shear processed to a certain extent. In this nonwoven fabric G, peeling occurs between each resin (oxymethylene polymer, PE) constituting the composite fiber by shear processing.

  Nonwoven fabric E is smooth and soft to the touch, has high nonwoven fabric strength derived from fiber strength, and is not easily torn. In addition, since the specific gravity of the oxymethylene polymer is large, the non-woven fabric E has a small diameter of the non-woven fabric because the non-woven fabric E has the same fineness, but the fine diameter of the non-woven fabric is large. Excellent.

  Nonwoven fabric F is smooth and has very high drape. In addition, because the constituent fibers are highly elastic, but the surface friction is low, the fiber entanglement does not proceed too much, and the bulky features, plumpness, and touch are good compared to the spunlace nonwoven fabric that does not normally bulk. .

  The nonwoven fabric G has a very good texture because the constituent fibers are at least partially exfoliated and made very fine.

Next, the surface material of the absorbent article of this invention is demonstrated based on the preferable embodiment, referring drawings. FIG. 1 is a perspective view showing a skin contact surface side of an absorbent article (a sanitary napkin) having a surface material according to an embodiment of the present invention, with a part cut away.
The surface material 1 of the absorbent article of the present embodiment is a surface material of the napkin 10 that covers the absorbent body 2 that absorbs body fluid, and is made of the above-described nonwoven fabric of the present invention.

  The napkin 10 has a vertically long shape including a liquid-permeable surface material 1, a liquid-retaining absorbent body 2, and a liquid-impermeable or water-repellent back material 3. The outer surface of the surface material 1 is a skin contact surface that contacts the skin when the napkin 10 is worn. The absorbent body 2 has a structure formed by wrapping a fiber stack containing fluff pulp and a superabsorbent polymer with absorbent paper such as tissue paper, but is not limited thereto. The outer surface of the back material 3 is a clothing contact surface (non-skin contact surface) on which the napkin 10 contacts the clothing. An adhesive layer (not shown) for fixing the napkin 10 to the undergarment is provided on the outer surface of the back material 3. The pressure-sensitive adhesive layer is formed, for example, in a rectangular shape, and is arranged on the outer surface of the back material 3 with its longitudinal direction coinciding with the longitudinal direction of the napkin 10, and before the napkin 10 is used, the pressure-sensitive adhesive layer Is covered with a release sheet (not shown) for protecting the film, or covered with a release-processed packaging sheet (not shown). The configuration of such a napkin 10 is the same as that conventionally known. As the absorber 2, the back sheet 3, and the pressure-sensitive adhesive layer, the same materials as those usually used in the technical field can be used. As long as the absorber 32 has a liquid retaining property, a material usually used for this type of article can be used without particular limitation.

  According to the napkin 10 of this example, since the surface material 1 is formed from the above-described nonwoven fabric of the present invention, the touch is good and soft, it is difficult to cause wrinkles and kinks, the liquid permeability is excellent, the liquid residue and Does not cause liquid return.

Next, the exterior material of the absorbent article of this invention is demonstrated based on the preferable embodiment, referring drawings. The top view which shows the skin contact surface side (surface sheet side) in the expansion | deployment state of the absorbent article (underpants type disposable diaper) which comprised the exterior | packing material concerning the Example of this invention is shown by FIG.
The packaging material 23 of the absorbent article of the present embodiment is a packaging material for the pants-type diaper 20 that covers the non-skin contact surface side of the absorbent main body 26 including the absorbent body 25 that absorbs bodily fluids. It consists of the nonwoven fabric of the invention.

  The diaper 20 is a liquid-permeable member that is attached to the base material sheet 21 with elastic members 22a, 22b, and 22c in an expanded state, and the inner side (skin contact surface side) of the outer material 23. The sheet is composed of a top sheet 24, a liquid-impermeable back sheet (not shown), and a vertically long absorbent main body 26 including a liquid-retaining absorbent 25 interposed between these sheets. The diaper 20 is formed into a pants shape by folding the exterior material 23 together with the absorbent main body 26 so that the abdomen A and the back B are overlapped and sealing the side seal part 27. Will be. The configuration itself of such a diaper 20 is the same as that conventionally known. As the elastic members 22a, 22b, and 22c, the top sheet 24, and the absorber 25, the same ones that are normally used in the technical field can be used.

The base material sheet 21 constituting the exterior material 23 is formed from the above-described nonwoven fabric of the present invention. The exterior material 23 is a structural member for holding firmly the discharge | exhaustion etc. from a body, without making it leak.
According to the diaper 20 of the present example, the exterior material 23 (base material sheet 21) is formed from the above-described nonwoven fabric of the present invention, so that it is smooth and feels good. Moreover, since the strength of the nonwoven fabric is high, it is difficult to break.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment.
For example, in the above embodiment, the sanitary napkin is given as one example of application of the surface material of the absorbent article of the present invention, but the surface material of the present invention can be applied to other absorbent articles as well. For example, the surface material of the present invention can be applied to disposable diapers, panty liners, incontinence liners, incontinence pads, and the like.
Moreover, in the said embodiment, although the underpants-type disposable diaper was mentioned as one of the application examples of the exterior material of the absorbent article of this invention, the exterior material of this invention is other absorbent articles which have an exterior material. Is also applicable.

It is the perspective view which notched and showed the skin contact surface side of the absorbent article (sanitary napkin) provided with the surface material in connection with the Example of this invention. It is a top view which shows the skin contact surface side (surface sheet side) in the expansion | deployment state of the absorbent article (pants type disposable diaper) which comprised the exterior | packing material concerning the Example of this invention.

Explanation of symbols

1 Surface material (nonwoven fabric)
2 Absorbent body 3 Back material 10 Sanitary napkin 20 Pants-type disposable diaper 21 Base sheet (nonwoven fabric)
22a, 22b, 22c Elastic member 23 Exterior material 24 Top sheet 25 Absorber 26 Absorbent body 27 Side seal part 27
A Ventral side B Back side

Claims (12)

  A nonwoven fabric for absorbent articles comprising a fiber layer, wherein some or all of the constituent fibers of the fiber layer are polyacetal fibers containing a polymer having an oxymethylene structural unit.   The nonwoven fabric according to claim 1, wherein the polymer is a copolymer of the oxymethylene structural unit and a structural unit composed of a component copolymerizable with the oxymethylene structural unit.   The nonwoven fabric according to claim 1 or 2, wherein a part or all of the polyacetal fiber contained in the fiber layer is a composite fiber of the polymer and a resin other than the polymer.   The nonwoven fabric according to claim 3, wherein the composite fiber is a parallel type or eccentric type composite fiber and expresses a three-dimensional manifested crimp.   The nonwoven fabric according to claim 3 or 4, wherein the other resin is a thermoplastic resin having a melting point higher than that of the polymer.   The nonwoven fabric according to claim 3 or 4, wherein the other resin is a thermoplastic resin having a melting point lower than that of the polymer. The polyacetal average fineness of the fibers is not more than 2 dtex, the nonwoven fabric according to any one of claims 1 to 6 basis weight of the fiber layer is 25 g / m ² or less.   The nonwoven fabric according to any one of claims 1 to 7, wherein the fiber layer is formed by heating a fiber web which is a precursor of the fiber layer and fusing constituent fibers of the fiber web.   The nonwoven fabric according to any one of claims 1 to 7, wherein the fiber layer is formed by entanglement of constituent fibers of a fiber web that is a precursor of the fiber layer.   A nonwoven fabric for absorbent articles comprising a fiber layer, wherein the fiber layer is laminated on the first layer, the first layer mainly comprising polyacetal fibers containing a polymer having an oxymethylene structural unit, and A non-woven fabric having a second layer mainly composed of fibers partially joined to the first layer and having a lower elongation recovery rate than the polyacetal fiber, and having an uneven shape on the surface of the second layer.   It is a surface material of the absorbent article which covers the absorber which absorbs a bodily fluid, Comprising: The surface material of the absorbent article which consists of a nonwoven fabric in any one of Claims 1-10.   It is the exterior material of the absorbent article which covers the non-skin contact surface side of the absorptive main body which comprises the absorber which absorbs a bodily fluid, Comprising: The exterior of the absorbent article which consists of a nonwoven fabric in any one of Claims 1-10 Wood.

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