JP4753852B2 - Elastic nonwoven fabric - Google Patents

Description

  The present invention relates to a stretchable nonwoven fabric.

  Various non-woven fabrics including fibers made of a polyolefin-based copolymer and having elongation are known. For example, Patent Document 1 describes a stretchable nonwoven fabric made of fibers containing a propylene / α-olefin random copolymer. This propylene / α-olefin random copolymer is polymerized by a metallocene catalyst, and the α-olefin content is 2 to 23 mol%. This nonwoven fabric exhibits stretchability by heat treatment. That is, the fiber containing the propylene / α-olefin random copolymer does not have elasticity itself. Therefore, this nonwoven fabric does not have sufficient stretch properties.

In Patent Document 2, a polyurethane non-woven fabric is arranged on one side of a melt blown non-woven fabric made of a polyolefin-based elastomer made of an ethylene / α-olefin copolymer, and a circular knitted fabric made of polyethylene terephthalate long fibers is arranged on the other side. A laminated body obtained by bonding the materials by calendering is described. The ethylene / α-olefin copolymer has a density of 0.90 g / cm ³ or more and an α-olefin content of 8 to 25 mol%. This laminate cannot be said to be sufficiently contractible after being stretched.

  As a stretchable nonwoven fabric using an ethylene / α-olefin copolymer, the present applicant has first made a hard elastic component made of crystalline polypropylene as a first component, a thermoplastic elastomer as a second component, and a first component as a first component. The sheath and the stretchable nonwoven fabric which consists of the core-sheath type elastic elastic composite fiber which makes the 2nd component a core, and the thermoplastic elastomer consists of the ethylene-alpha-olefin copolymer manufactured using the metallocene catalyst was proposed ( (See Patent Document 3). This nonwoven fabric has good stretchability and has a cloth-like texture. However, a nonwoven fabric with higher stretchability is desired.

JP 2003-49352 A JP 2003-53894 A JP-A-9-291454

  Accordingly, an object of the present invention is to provide a stretchable nonwoven fabric in which various properties including stretchability are further improved.

The present invention has an elastic fiber layer containing an elastic fiber containing a polyolefin-based elastomer mainly composed of propylene, and another elastic fiber or non-elastic fiber different from the elastic fiber,
The polyolefin elastomer achieves the object by providing a stretchable nonwoven fabric having a propylene content of 80 to 90% by weight and a density of 0.855 to 0.880 g / cm ³ .

  The stretchable nonwoven fabric of the present invention has higher stretch properties than conventional stretchable nonwoven fabrics. Also, the tensile strength is increased. Furthermore, the polyolefin-based elastomer has high fusion properties with the inelastic fiber layer. As a result, when the non-elastic fiber layer is laminated on the elastic fiber layer, the bonding between both layers becomes good and delamination hardly occurs.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The stretchable nonwoven fabric of the present invention has an elastic fiber layer. The stretchable nonwoven fabric may be composed only of an elastic fiber layer, or a substantially inelastic nonelastic fiber layer may be laminated on at least one surface thereof as shown in FIG. The elastic fiber layer includes elastic fibers. An elastic fiber layer consists only of elastic fibers, or contains elastic fibers and extensible non-elastic fibers. One type or two or more types of elastic fibers can be used. When inelastic fibers are contained in the elastic fiber layer, one type or two or more types of inelastic fibers can be used.

  At least one of the elastic fibers is an elastic fiber containing a polyolefin-based elastomer mainly composed of propylene. The elastic fiber contained in the elastic fiber layer is only the elastic fiber containing the polyolefin-based elastomer or the elastic fiber and another elastic fiber different from the elastic fiber.

  The elastic fiber containing the polyolefin-based elastomer is composed only of the polyolefin-based elastomer, or is composed of the polyolefin-based elastomer and one or more other resins.

The polyolefin-based elastomer used in the present invention is characterized by containing a specific amount of propylene and having a low density. The polyolefin elastomer is mainly composed of propylene, that is, a propylene / α-olefin copolymer. This polyolefin-based elastomer has a propylene content of 80 to 90% by weight. The polyolefin elastomer has a density of 0.855 to 0.880 g / cm ³ . The propylene content in this range is at a low level compared to the propylene content of the conventionally used polypropylene elastomer, and the density in this range is compared to the density of the polypropylene elastomer used conventionally. It is at a low level. That is, the polyolefin-based elastomer used in this embodiment is characterized by having a low propylene content and a low density. By using an elastic fiber containing a polyolefin-based elastomer having such characteristics as a constituent resin, the stretchable nonwoven fabric of the present invention has higher stretchability than that of the conventional one.

In particular, when the polyolefin-based elastomer has a low propylene content and a low density, yarn breakage hardly occurs when melt spinning an elastic fiber, and a continuous fiber having a small diameter can be easily produced. The ability to reduce the diameter of the elastic fiber greatly contributes to the improvement of stretchability. The fact that elastic fibers can be made into continuous fibers (filaments) also greatly contributes to the improvement of stretch properties. Moreover, when the polyolefin-based elastomer has a low propylene content and a low density, the handleability of the elastic fiber itself (for example, it is difficult to stick) is improved. Furthermore, fuzz on the surface of the stretchable nonwoven fabric can be suppressed. In addition, the tensile strength of the elastic fiber itself increases, and consequently the tensile strength of the stretchable nonwoven fabric also increases. Moreover, as will be described later, when the elastic fiber layer and the non-elastic fiber layer are laminated, the fusibility of both layers is increased. From these viewpoints, when the propylene content of the polyolefin-based elastomer is particularly 82 to 88% by weight, the above characteristics are further improved. Setting the density of the polyolefin-based elastomer to 0.860 to 0.870 g / cm ³ has the same effect.

The propylene content in the polyolefin elastomer is measured by the following method. A ¹³ C-NMR measurement is performed on the polyolefin-based elastomer. From the obtained NMR spectrum, the weight ratio of propylene and the other α-olefin component is calculated. And what converted the weight ratio of propylene into 100% is made into propylene content rate. The density of the polyolefin-based elastomer is measured in accordance with JIS-K7112 C method (floating method). The density measurement environment is 23 ° C. and 50% RH, and ethanol / distilled water is used as the immersion liquid.

  There is no particular limitation on the polymerization method of the polyolefin-based elastomer, but a metallocene catalyst is preferably used as the polymerization catalyst because the resulting polyolefin-based elastomer becomes homogeneous. As a polymerization method in the case of using a metallocene catalyst, a slurry method using an inert solvent, a gas phase method using no solvent, a bulk polymerization method using a monomer as a solvent, or the like can be used. Metallocene catalysts are metallocene, which is a compound having a structure in which a transition metal such as titanium, zirconium, hafnium or the like is sandwiched between unsaturated cyclic compounds containing a π-electron cyclopentadienyl group or substituted cyclopentadienyl group, and an aluminum compound. And a cocatalyst such as Examples of the metallocene include titanocene and zirconocene. Examples of the aluminum compound include alkylaluminoxane, alkylaluminum, aluminum halide, alkylaluminum halide and the like.

  Polyolefin elastomers have a melt flow rate (MFR) of 2 to 350 g / 10 min, particularly 20 to 200 g / 10 min, making it easier for yarn breakage when melt spinning an elastic fiber, and for a continuous finer diameter. This is preferable because the fiber can be easily produced. MFR is measured according to ASTM D-1238. The measurement conditions are 230 ° C. and a load of 2.16 kg.

  The polyolefin-based elastomer has a heat of fusion value A of 2 to 20 mJ / mg, preferably 4 to 18 mJ / mg, and a heat of fusion value B of 12 to 24 mJ / mg, particularly 13 to 22 mJ / mg. preferable. It is preferable for each value of heat of fusion to be in the above-mentioned range since the stretchability is improved while the tensile strength is kept moderate and the melt spinnability is improved. Each value of heat of fusion is determined by differential scanning calorimetry (DSC). The heat of fusion value A is obtained from the calorific value at the endothermic peak appearing at 160 to 165 ° C. by obtaining a DSC curve while raising the temperature at 10 ° C./min. The heat of fusion value B is obtained from the sum of the heat value at the endothermic peak appearing at 40-60 ° C. and the heat of fusion value A, while the DSC curve is obtained while raising the temperature at 10 ° C./min.

  Examples of the α-olefin copolymerized with propylene include α-olefins having 2 or 4 to 20 carbon atoms. For example, ethylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene and the like. These α-olefins can be used alone or in combination of two or more. Of these α-olefins, ethylene and 1-butene are particularly preferably used. In particular, those obtained by polymerizing α-olefin at positions other than both terminal blocks (terminal block molecular weight of 5000 or more) are preferable.

  The polyolefin-based elastomer preferably has a weight average molecular weight of 140,000 to 280,000, particularly 150,000 to 240,000.

  As described above, the elastic fiber containing the polyolefin-based elastomer may be composed of only the polyolefin-based elastomer as a resin component, or the polyolefin-based elastomer and one or more other resins. It may contain and may be comprised. In any case, the elastic fiber may be in the form of a short fiber or in the form of a long fiber. When the elastic fiber contains the polyolefin-based elastomer and other resins, the content of the polyolefin-based elastomer in the elastic fiber is preferably 10 to 99% by weight, particularly 50 to 80% by weight.

  When the elastic fiber contains the polyolefin elastomer and other resins, examples of the other resins include rubber, styrene elastomers such as SBS, SIS, SEBS, and SEPS, polyester elastomers, polyurethane elastomers, and the like. It is possible to use a resin made of a thermoplastic elastomer or the like. These can also be used in combination of two or more.

  When the elastic fiber contains the polyolefin elastomer and other resin, the fiber form of the elastic fiber includes (a) a single fiber composed of a blend polymer of the polyolefin elastomer and another resin, and (b) The form of the composite fiber containing this polyolefin-type elastomer and other resin is mentioned. Examples of the composite fiber include a core-sheath composite fiber, a side-by-side composite fiber, and a split fiber.

  Since the polyolefin-based elastomer has the propylene content and density described above, the spinnability is very good even if it is melt-spun alone. Therefore, it is not necessary to improve spinnability by using other resins in combination. When other resins are used in combination, the inherent elasticity of the polyolefin-based elastomer may be impaired. That is, it is particularly preferable that the elastic fiber is composed only of the polyolefin-based elastomer as a resin component.

  As described above, the elastic fiber layer may contain other elastic fibers different from the elastic fibers in addition to the elastic fibers containing the polyolefin-based elastomer. The other elastic fiber is not particularly limited as long as it can form a nonwoven fabric together with the elastic fiber containing the polyolefin-based elastomer. Examples of other elastic fibers include elastic fibers containing thermoplastic elastomers such as styrene elastomers, polyester elastomers, and polyurethane elastomers. The blending ratio of the other elastic fiber with respect to the weight of the entire elastic fiber is preferably 5 to 80% by weight, particularly 5 to 50% by weight.

  The elastic fiber layer includes non-elastic fibers having extensibility in addition to the elastic fibers containing the polyolefin elastomer or in addition to the elastic fibers and other elastic fibers different from the elastic fibers. It may be. Examples of the inelastic fiber include fibers made of polyethylene (PE), polypropylene (PP), polyester (PET or PBT), polyamide, and the like. Inelastic fibers may be short fibers or long fibers, and may be hydrophilic or water repellent. Moreover, a core-sheath type or side-by-side type composite fiber, a split fiber, a modified cross-section fiber, a crimped fiber, a heat-shrinkable fiber, or the like can also be used. These fibers can be used alone or in combination of two or more. When the elastic fiber layer is configured to include an elastic fiber and a non-elastic fiber, the weight ratio of the former / the latter is 20/80 to 80/20, particularly 30/70 to 70/30. It is preferable from the viewpoints of having excellent stretch properties, realizing high strength, good touch, and improved texture.

  As described above, the stretchable nonwoven fabric of the present invention may be composed of only an elastic fiber layer, or a substantially inelastic nonelastic fiber layer may be laminated on at least one surface thereof. . FIG. 1 shows a schematic diagram of a cross-sectional structure in a preferred embodiment of the stretchable nonwoven fabric of the present invention. The stretchable nonwoven fabric 10 of this embodiment is configured by laminating the same or different substantially inelastic non-elastic fiber layers 2 and 3 on both surfaces of the elastic fiber layer 1.

  The elastic fiber layer 1 is an aggregate including elastic fibers. The elastic fiber layer 1 has a property that it can be stretched and contracts when released from the stretched force. The elastic fiber layer 1 preferably has a residual strain of 20% or less, particularly 10% or less when contracted after 100% elongation in at least one direction parallel to the surface. This value is preferably satisfied in at least one of the MD direction and the CD direction, and more preferably satisfied in both directions.

  The elastic fiber contained in the elastic fiber layer 1 is formed by, for example, a melt blown method in which a molten resin is extruded from a nozzle hole, and the extruded molten resin is elongated by hot air to thin the fiber, or a semi-molten resin is used. Manufactured by a spunbond method of drawing with cold air or a mechanical draw machine. Elastic fibers can also be produced by a spinning blow method, which is a special method of the melt blow method, which is a combination of the melt blow method and the spun bond method.

  The elastic fiber layer 1 may be in the form of a web or elastic fabric containing elastic fibers. For example, it may be a web or a nonwoven fabric formed by a spinning blow method, a spun bond method, a melt blow method, or the like. Particularly preferred is a web obtained by the spinning blow method.

  In the spinning blown method, a pair of hot air discharge portions are disposed opposite to each other around the nozzle, and a pair of cold air discharge portions are disposed opposite to each other downstream from the nozzle. Use a spinning die. According to the spinning blow method, the stretch of the molten fiber by hot air and the cold stretch by cold air are continuously performed, so that there is an advantage that the stretchable fiber can be easily formed. Further, since the fibers do not become too dense and elastic fibers having a thickness similar to short fibers can be formed, there is an advantage that a nonwoven fabric with high air permeability can be obtained. Further, according to the spinning blow method, a continuous filament web can be obtained. The continuous filament web is very advantageous in the present embodiment because it is less likely to break at the time of high elongation than the short fiber web and easily develops elasticity.

  As the spinning die used in the spinning blow method, for example, the one shown in FIG. 2 of JP-A-3-174008 or the one shown in FIGS. 1 to 4 of Japanese Patent No. 3335949 can be used.

  Inelastic fiber layers 2 and 3 have extensibility, but are substantially inelastic. The stretchability here refers to the case where the constituent fibers themselves are stretched, and even if the constituent fibers themselves are not stretched, the two fibers that have been heat-sealed at the intersection of the fibers are separated from each other, or the fibers are thermally fused. The three-dimensional structure formed by a plurality of fibers may be structurally changed due to wearing or the like, and the constituent fibers may be broken, and the whole fiber layer may be elongated.

  As the fibers constituting the non-elastic fiber layers 2 and 3, the same fibers as those described above as the stretchable non-elastic fibers that can be included in the elastic fiber layer 1 can be used. The inelastic fiber layers 2, 3 can be continuous filaments or short fiber webs or nonwovens. In particular, a short fiber web is preferable because thick and bulky inelastic fiber layers 2 and 3 can be formed. The two inelastic fiber layers 2 and 3 may be the same or different with respect to the material, basis weight, thickness, and the like of the constituent fibers. In the case of a core-sheath type composite fiber, the core is preferably PET or PP, and the sheath is preferably a low melting point PET, PP or PE. In particular, the use of these composite fibers is preferable in that the heat fusion with the constituent fibers of the elastic fiber layer becomes strong and the delamination hardly occurs.

  At least one of the two non-elastic fiber layers 2 and 3 is preferably 1.2 to 20 times, particularly 1.5 to 5 times as thick as the elastic fiber layer 1. On the other hand, regarding the basis weight, it is preferable that the basis weight of the elastic fiber layer is higher than the basis weight of at least one of the two inelastic fiber layers 2 and 3. In other words, the non-elastic fiber layer is preferably thicker and has a smaller basis weight than the elastic fiber layer. By having such a relationship between the thickness and the basis weight, the inelastic fiber layer becomes thicker and bulkier than the elastic fiber layer. As a result, the stretchable nonwoven fabric 10 is soft and has a good texture.

  Regarding the thickness of the non-elastic fiber layers 2 and 3, it is preferably 0.05 to 5 mm, particularly preferably 0.1 to 0.5 mm. On the other hand, the thickness of the elastic fiber layer 1 is preferably smaller than the thickness of the non-elastic fiber layers 2 and 3, specifically 0.01 to 2 mm, particularly 0.1 to 0.2 mm. preferable. The thickness can be measured by observing a cross section of the stretchable nonwoven fabric with a microscope at a magnification of 50 to 200 times, obtaining an average thickness in each visual field, and obtaining an average value of the thicknesses of three visual fields.

For the basis weight itself of the non-elastic fibrous layers 2 and 3, from the viewpoints of and residual strain which covers the surface of the elastic fiber layer uniform, respectively 1~60g / m ^2, to be particularly 5 to 15 g / m ² preferable. On the other hand, the basis weight itself of the elastic fiber layer 1 is preferably larger than the basis weight of the non-elastic fiber layers 2 and 3 from the viewpoint of stretch characteristics and residual strain. Specifically, it is preferably 5 to 80 g / m ² , particularly 10 to 40 g / m ² .

  Regarding the fiber diameter of the constituent fibers, the fiber diameter of the constituent fibers of the elastic fiber layer 1 is 1.2 to 5 times the fiber diameter of the constituent fibers of at least one of the non-elastic fiber layers 2 and 3, particularly 1.2 to 2.. It is preferably 5 times. In addition to this, the constituent fiber of the elastic fiber layer 1 has a fiber diameter of 5 μm or more, particularly 10 μm or more, preferably 100 μm or less, particularly 40 μm or less, from the viewpoint of air permeability and stretchability. On the other hand, the constituent fibers of the inelastic fiber layers 2 and 3 preferably have a fiber diameter of 1 to 30 μm, particularly 10 to 20 μm. That is, as the constituent fibers of the non-elastic fiber layers 2 and 3, it is preferable to use those that are thinner than the constituent fibers of the elastic fiber layer 1. Thereby, the fusion point of the constituent fibers of the non-elastic fiber layers 2 and 3 located on the surface layer is increased. The increase in the fusion point is effective in preventing the occurrence of fuzz in the stretchable nonwoven fabric 10. Furthermore, the stretchable nonwoven fabric 10 having a good touch can be obtained by using thin fibers.

  As shown in FIG. 1, the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 are bonded to the entire surface by thermal fusion of fiber intersections in a state where the constituent fibers of the elastic fiber layer 1 maintain the fiber form. It is preferable. That is, it is preferable that the joining state differs from the conventional stretchable nonwoven fabric that is partially joined. In the stretchable nonwoven fabric of this embodiment, when the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 are entirely bonded, the interface between the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 and In the vicinity thereof, the intersections of the constituent fibers of the elastic fiber layer 1 and the constituent fibers of the non-elastic fiber layers 2 and 3 are heat-sealed, and are joined substantially uniformly over the entire surface. By being bonded over the entire surface, it is possible to prevent the floating between the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3, that is, the formation of a space by separating both layers. When floating occurs between the two layers, there is no sense of unity between the elastic fiber layer and the non-elastic fiber layer, and the texture of the stretchable nonwoven fabric 10 tends to decrease. According to a preferred embodiment of the present invention in which the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 are bonded to each other, a stretchable nonwoven fabric having a multi-layer structure with a sense of unity, such as a single nonwoven fabric, is provided.

  “The state in which the constituent fibers of the elastic fiber layer 1 maintain the fiber form” means that even if most of the constituent fibers of the elastic fiber layer 1 are given heat, pressure, or the like, a film or film- A state in which the fiber structure is not deformed. There exists an advantage that sufficient breathability is provided to the elastic nonwoven fabric 10 of this embodiment because the constituent fiber of the elastic fiber layer 1 is in the state of maintaining the fiber form.

  In the elastic fiber layer 1, the intersections of the constituent fibers are thermally fused in the layer. Similarly, in the inelastic fiber layers 2 and 3, the intersections of the constituent fibers are heat-sealed in the layers.

  In at least one of the two non-elastic fiber layers 2 and 3, a part of the constituent fibers are in the elastic fiber layer 1, and / or a part of the constituent fibers of the elastic fiber layer is at least one of the two. The inelastic fiber layers 2 and 3 are in a state of entering. By being in such a state, integration of the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 is promoted, and it is more effectively prevented that floating occurs between both layers. As a result, the layers are combined with each other following the surface of each layer. Part of the constituent fibers of the non-elastic fiber layer enters the elastic fiber layer 1 and remains there, or penetrates through the elastic fiber layer 1 and reaches the other non-elastic fiber layer. When the surface connecting the surface fibers in each layer is assumed macroscopically, a part of the constituent fibers of the other layer enters the cross-sectional thickness direction of the layer from this surface into the fiber space formed inside the layer. It is out. When the constituent fibers of the non-elastic fiber layer enter the elastic fiber layer 1 and remain there, it is preferable that the constituent fibers are further entangled with the constituent fibers of the elastic fiber layer 1. Similarly, when the constituent fiber of the non-elastic fiber layer penetrates through the elastic fiber layer 1 and reaches the other non-elastic fiber layer, the constituent fiber is the same as the constituent fiber of the other non-elastic fiber layer. Preferably they are entangled. This is confirmed by the fact that no space is substantially formed between the layers when the cross section in the thickness direction of the stretchable nonwoven fabric is observed with an SEM or a microscope. The term “entanglement” as used herein means a state in which fibers are sufficiently intertwined, and a state in which the fiber layers are simply overlapped is not included in the intertwining. Whether or not they are entangled, for example, after applying the air-through method without overlapping the fiber layer and heat fusion, the force required to peel the fiber layer from the state where the fiber layer is simply overlapped In comparison with the force to peel off the fiber layer, if there is a substantial difference between them, it can be determined that they are entangled.

  In order to allow the constituent fibers of the non-elastic fiber layer to enter the elastic fiber layer and / or to allow the constituent fibers of the elastic fiber layer to enter the non-elastic fiber layer, the constituent fibers of the non-elastic fiber layer and the configuration of the elastic fiber layer It is preferable that at least one of the non-elastic fiber and the elastic fiber is in a web state (a state where the fiber is not heat-sealed) before the process of thermally fusing the fiber. From the viewpoint of allowing the constituent fibers to enter other layers, the fiber layer in the web state is preferable because the short fibers have a higher degree of freedom than the long fibers.

  Further, it is preferable to use the air-through method in order to allow the constituent fibers of the non-elastic fiber layer to enter the elastic fiber layer 1 and / or to allow the constituent fibers of the elastic fiber layer to enter the non-elastic fiber layer. By using the air-through method, the constituent fibers can be made to enter the opposing fiber layer, and the constituent fibers can be easily made to enter from the opposing fiber layer. In addition, by using the air-through method, it becomes easy to allow the constituent fibers of the inelastic fiber layer to enter the elastic fiber layer 1 while maintaining the bulkiness of the inelastic fiber layer. In the case where the constituent fibers of the non-elastic fiber layer are allowed to penetrate the elastic fiber layer 1 and reach the other non-elastic fiber layer, it is preferable to use the air-through method in the same manner. In particular, it is preferable to laminate an inelastic fiber layer in a web state with the elastic fiber layer and use the air-through method. In this case, the constituent fibers of the elastic fiber layer may be heat-sealed. Furthermore, as will be described later in the production method, by performing the air-through method under specific conditions, and to improve the flow of hot air, the breathability of the stretchable nonwoven fabric, particularly the breathability of the elastic fiber layer is high. By doing, a fiber can be made to penetrate more uniformly. A method other than the air-through method, for example, a method of spraying steam can also be used. It is also possible to use a spunlace method, a needle punch method, etc., but in that case, the bulkiness of the inelastic fiber layer is impaired, or the constituent fibers of the elastic fiber layer appear on the surface. The texture of the resulting stretchable nonwoven fabric tends to decrease.

  In particular, when the constituent fibers of the non-elastic fiber layer are entangled with the constituent fibers of the elastic fiber layer 1, it is preferable that the non-elastic fiber layer is entangled only by the air-through method.

  In order to entangle the fibers by the air-through method, the gas blowing pressure, the blowing speed, the basis weight and thickness of the fiber layer, the conveying speed of the fiber layer, and the like may be appropriately adjusted. By simply adopting the conditions for producing a normal air-through nonwoven fabric, the constituent fibers of the inelastic fiber layer and the constituent fibers of the elastic fiber layer 1 cannot be entangled. As will be described later in the production method, the stretchable nonwoven fabric intended in the present invention is obtained by performing the air-through method under specific conditions.

  In the air-through method, generally, a gas heated to a predetermined temperature is penetrated in the thickness direction of the fiber layer. In that case, fiber entanglement and fiber intersection fusion occur simultaneously. However, in this embodiment, it is not essential to fuse the fiber intersections between the constituent fibers in each layer by the air-through method. In other words, in the air-through method, the constituent fibers of the non-elastic fiber layer are allowed to enter the elastic fiber layer 1 or the constituent fibers are entangled with the constituent fibers of the elastic fiber layer 1 and the non-elastic fiber layer This operation is necessary for heat-sealing the constituent fibers of the elastic fiber layer and the constituent fibers of the elastic fiber layer. The direction in which the fibers enter varies depending on the passing direction of the heated gas and the positional relationship between the inelastic fiber layer and the elastic fiber layer. The inelastic fiber layer is preferably an air-through nonwoven fabric in which fiber intersections are fused in the constituent fibers by an air-through method.

  As is apparent from the above description, in the preferred form of the stretchable nonwoven fabric of the present embodiment, the elastic fiber in a state in which the constituent fibers maintain the fiber form inside the thickness direction of the substantially inelastic inelastic air-through nonwoven fabric. Layer 1 is included, and a part of the constituent fibers of the air-through nonwoven fabric enters the elastic fiber layer 1 and / or a part of the constituent fibers of the elastic fiber layer enters the inelastic fiber layer. It has become. In a more preferred form, some of the constituent fibers of the air-through nonwoven fabric are entangled only with the constituent fibers of the elastic fiber layer 1 by the air-through method. Since the elastic fiber layer 1 is included in the air-through nonwoven fabric, the constituent fibers of the elastic fiber layer 1 are not substantially present on the surface of the stretchable nonwoven fabric. This is preferable from the point that the stickiness peculiar to an elastic fiber does not arise.

  In the stretchable nonwoven fabric 10 of this embodiment, as shown in FIG. 1, minute recesses are formed in the inelastic fiber layers 2 and 3. Thereby, the cross section of the stretchable nonwoven fabric 10 has a waveform shape microscopically. This waveform shape is generated by stretching 10 stretchable nonwoven fabrics, as will be described later in the manufacturing method. This corrugated shape is generated as a result of imparting stretchability to the stretchable nonwoven fabric 10 and does not significantly affect the texture of the nonwoven fabric 10 itself.

  Although not shown in FIG. 1, the stretchable nonwoven fabric 10 of the present embodiment may be embossed. Embossing is performed for the purpose of further increasing the bonding strength between the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3. Therefore, if the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 can be sufficiently joined by the air-through method, there is no need to perform embossing. In the embossing, the constituent fibers are joined to each other. However, unlike the air-through method, the constituent fibers are not entangled depending on the embossing.

  The stretchable nonwoven fabric 10 of this embodiment has stretchability in at least one direction in the in-plane direction. It may have elasticity in all directions in the plane. In that case, it is not hindered that the degree of elasticity varies depending on the direction. With respect to the direction of expansion and contraction, the degree of elasticity is preferably 20 to 500 cN / 25 mm, particularly 40 to 150 cN / 25 mm, at 100% elongation. Further, the residual strain when contracted from the 100% stretched state is preferably 15% or less, particularly preferably 10% or less.

The stretchable nonwoven fabric 10 of this embodiment can be used for various uses such as surgical clothes and cleaning sheets from the viewpoint of its good texture, fuzz prevention, stretchability, and breathability. In particular, it is preferably used as a constituent material of absorbent articles such as sanitary napkins and disposable diapers. For example, it can be used as a sheet for providing elastic stretchability to a sheet constituting the outer surface of a disposable diaper, a waistline part, a waist part, a leg periphery part, or the like. Moreover, it can be used as a sheet or the like for forming a stretchable wing of a napkin. Moreover, even if it is another site | part, it can be used for the site | part etc. which want to provide a stretching property. The basis weight and thickness of the stretchable nonwoven fabric can be appropriately adjusted according to the specific application. For example, when used as a constituent material of an absorbent article, it is desirable that the basis weight is about ²⁰ to 160 g / m ² and the thickness is about 0.1 to 5 mm. In addition, the stretchable nonwoven fabric of the present invention is flexible and has high air permeability because the constituent fibers of the elastic fiber layer maintain the fiber form. Regarding the bending stiffness which is a measure of flexibility, the stretchable nonwoven fabric of the present invention preferably has a bending stiffness value as low as 10 g / 30 mm or less. Regarding the air permeability, the air permeability is preferably 16 m / (kPa · s) or more. The elongation is preferably 100% or more.

  The bending stiffness is measured in accordance with JIS L-1096, and is obtained as an average value when bent in the flow direction and in a direction perpendicular to the flow direction, respectively, under the conditions of an indentation amount of 8 mm by a handle ohmmeter and a slit width of 10 mm. The air permeability is obtained as the reciprocal of the air resistance measured by AUTOMATIC AIR-PERMEABILITY TESTER KES-F8-AP1 manufactured by Kato Tech.

  Next, the preferable manufacturing method of the elastic nonwoven fabric 10 of this embodiment is demonstrated, referring FIG. FIG. 2 schematically shows a preferable manufacturing apparatus used in the method for manufacturing the stretchable nonwoven fabric 10 of the present embodiment. The apparatus shown in FIG. 2 includes a web forming unit 100, a hot air processing unit 200, and a stretching unit 300 in this order from the upstream side to the downstream side of the manufacturing process.

  The web forming unit 100 includes a first web forming device 21, a second web forming device 22, and a third web forming device 23. A card machine is used as the first web forming device 21 and the third web forming device 23. As the card machine, the same card machines as those normally used in the technical field can be used without particular limitation. On the other hand, a spinning blown spinning device is used as the second web forming device 22. In the spinning blown spinning apparatus, a pair of hot air discharge portions are arranged opposite to each other around the nozzle near the tip of the molten polymer discharge nozzle, and a pair of cold air discharge portions downstream of the nozzle are centered on the nozzle. Opposing spinning dies are provided. As the spinning die used in the spinning blow method, for example, the one shown in FIG. 2 of JP-A-3-174008 or the one shown in FIGS. 1 to 4 of Japanese Patent No. 3335949 can be used.

  The hot air processing unit 200 includes a hot air furnace 24. In the hot stove 24, heated gas heated to a predetermined temperature, particularly heated air is blown out. When three layers of webs that are superimposed on each other are introduced into the hot stove, the heated gas is forced to penetrate from the top to the bottom of the web, in the opposite direction, or in both directions.

  The stretching unit 300 includes a weak joining device 25 and a stretching device 30. The weak joining device 25 includes a pair of embossing rolls 26 and 27. The weak joining device 25 is for ensuring the joining of the web of each layer in the fiber sheet formed by the hot air processing unit 200. A stretching device 30 is disposed downstream of the weak joining device 25 and adjacent thereto. The stretching device 30 includes a pair of concave and convex rolls 33 and 34 in which large-diameter portions 31 and 32 and small-diameter portions (not shown) are alternately formed in the axial direction and can be engaged with each other. . When the fiber sheet is caught between both the uneven rolls 33 and 34, the fiber sheet is stretched in the axial direction of the roll (that is, the width direction of the sheet).

  When the manufacturing method of the elastic nonwoven fabric using the apparatus which has the above structure is demonstrated, first, a pair of web which consists of the same or different inelastic fiber will be distribute | arranged to each surface of the web which consists of elastic fiber. The “web made of elastic fibers” means not only a web made only of elastic fibers but also an elastic fiber layer (layer indicated by reference numeral 1 in FIG. 1) formed from the web in a range that does not impair the elastic elasticity. Webs containing a small amount of inelastic fibers in addition to the fibers are also included.

  As shown in FIG. 2, in the web forming unit 100, inelastic short fibers are used as a raw material, an inelastic fiber web 3 ′ is manufactured by a card machine which is the first web forming device 21, and continuously conveyed in one direction. Let Fibers spun by a spinning blown spinning device that is the second web forming device 22 are deposited on a conveyor made of a collection net using elastic resin made of polyolefin elastomer or the like as a raw material, and include continuous filaments of elastic fibers. An elastic fiber web 1 'is produced. This is peeled off from the conveyor and laminated on the inelastic fiber web 3 ′ formed by the first web forming device 21 and continuously conveyed in one direction. On the elastic fiber web 1 ′, a non-elastic fiber web 2 ′ manufactured by a card machine which is the third web forming device 23 is further laminated.

  When the spinning blow method is used to form the elastic fiber web 1 ', there is an advantage that the stretchable fibers can be easily formed because the melted fibers are continuously stretched by hot air and cold stretched by cold air. Further, since the fibers do not become too dense and elastic fibers having a thickness similar to short fibers can be formed, there is an advantage that a nonwoven fabric with high air permeability can be obtained. Further, according to the spinning blow method, a continuous filament web can be obtained. The continuous filament web is very advantageous in the present embodiment because it is less likely to break at the time of high elongation than the short fiber web and easily develops elasticity.

  When the elastic fiber web 1 'is composed of, for example, two kinds of fibers, specifically, the elastic fiber web 1' is composed of elastic fibers containing the polyolefin-based elastomer and other elastic fibers different from the elastic fibers. In the case where it is constituted, or in the case where it is constituted by the elastic fiber containing the polyolefin-based elastomer and the non-elastic fiber, the spinning die of the spinning blown spinning device shown in FIG. Can be used. The spinning die shown in FIG. 3 has a structure in which spinning nozzles A and spinning nozzles B are alternately arranged. From the spinning nozzle A, the resin containing the polyolefin-based elastomer is discharged. On the other hand, another thermoplastic elastomer or inelastic resin is discharged from the spinning nozzle B.

  The laminate of the three webs is sent to an air-through hot air furnace 24 where hot air treatment is performed. By the hot air treatment, the intersections of the fibers are thermally fused, and the elastic fiber web 1 'is bonded to the non-elastic fiber webs 2' and 3 'on the entire surface. In the hot air treatment, it is preferable that the webs of the respective layers are not integrated. As a result, the bulky and thick state of each web is maintained even after the hot air treatment, and an elastic nonwoven fabric having a good texture can be obtained.

  In addition to heat-sealing the intersections of the fibers by hot air treatment and joining the webs of the respective layers over the entire surface, some of the constituent fibers of the non-elastic fiber web 2 ′ located mainly on the hot air blowing surface side are elastic It is preferable to let the fiber web 1 'enter. In addition, by controlling the conditions of the hot air treatment, it is preferable that some of the constituent fibers of the non-elastic fiber web 2 ′ enter the elastic fiber web 1 ′ and further entangle with the constituent fibers of the web 1 ′. . Alternatively, it is preferable that a part of the constituent fibers of the non-elastic fiber web 2 ′ penetrate the elastic fiber web 1 ′ to reach the non-elastic fiber web 3 ′ and entangle with the constituent fibers of the web 3 ′. .

A part of the constituent fibers of the non-elastic fiber web 2 ′ enter the elastic fiber web 1 ′ and / or a part of the constituent fibers of the elastic fiber web 1 ′ enter the non-elastic fiber web 2 ′. The conditions are preferably a hot air flow rate of 0.4 to 3 m / second, a temperature of 80 to 160 ° C., a conveyance speed of 5 to 200 m / minute, and a heat treatment time of 0.5 to 10 seconds. Particularly preferred is a hot air flow rate of 1 to 2 m / sec. The above conditions are also preferred in terms of softening the fibers and allowing them to penetrate uniformly and fusing the fibers. Further, the fibers can be entangled by setting the hot air flow rate to 3 to 5 m / sec and the blowing pressure to 0.1 to 0.3 kg / cm ² . When the air permeability of the elastic fiber web 1 ′ is 8 m / (kPa · s) or more, more preferably 24 m / (kPa · s) or more, the flow of hot air is improved and the fibers can be more uniformly entrained. Therefore, it is preferable. Further, the fiber is well fused and the maximum strength is increased. In addition, fuzz is prevented.

  In the hot air treatment, a part of the constituent fibers of the non-elastic fiber web 2 ′ enters the elastic fiber web 1 ′, and at the same time, the constituent fibers of the non-elastic fiber web 2 ′ and / or the configuration of the non-elastic fiber web 3 ′. It is preferable that the fibers and the constituent fibers of the elastic fiber web 1 ′ are heat-sealed at their intersections. In this case, the hot air treatment is preferably performed under conditions such that the elastic fiber after the hot air treatment maintains the fiber form. That is, it is preferable to prevent the constituent fibers of the elastic fiber web 1 'from forming a film or film-fiber structure by hot air treatment. In the hot air treatment, the constituent fibers of the non-elastic fiber web 2 ′ are heat-sealed at the intersection, and similarly, the constituent fibers of the elastic fiber web 1 ′ and the constituent fibers of the non-elastic fiber web 3 ′ are the intersection. Heat fusion.

  The fiber sheet 10B in which the three webs are integrated is obtained by the air-through hot air treatment. The fiber sheet 10B has a long band shape having a certain width and extending in one direction. The fiber sheet 10B is then conveyed to the stretching unit 300. In the stretching unit 300, the fiber sheet 10 </ b> B is first transported to the weak joining device 25. The weak joining device 25 is composed of an embossing device provided with a metal embossing roll 26 in which embossing convex portions are regularly arranged on the peripheral surface and a metal or resin receiving roll 27 arranged opposite thereto. The fiber sheet 10B is subjected to hot embossing by the weak joining device 25. As a result, a fiber sheet 10A that has been embossed is obtained. In addition, since the webs of the respective layers are joined and integrated by thermal fusion performed by the hot air processing unit 200 prior to the hot embossing by the weak joining device 25, the hot embossing by the weak joining device 25 is performed according to the present invention. Is not essential. When it is desired to ensure the joining and integration of the webs of each layer, the hot embossing by the weak joining device 25 is effective. Moreover, according to the weak joining apparatus 25, in addition to the joining integration of the web of each layer, there exists an advantage that the fluff of the fiber sheet 10A can be suppressed. Examples of a method for weakly bonding the fiber sheet 10B include ultrasonic bonding, calendar bonding with a flat roll, and steam jet bonding in addition to the above-described hot embossing.

  Since the hot embossing by the weak joining apparatus 25 is performed in an auxiliary manner to the heat fusion performed by the hot air processing unit 200, the processing conditions may be relatively mild. Conversely, if the conditions for hot embossing are severe, the bulkiness of the fiber sheet 10A is impaired, and a fiber film is formed, which negatively affects the texture and breathability of the finally obtained stretchable nonwoven fabric. From such a viewpoint, the linear pressure of hot embossing and the heating temperature of the embossing roll are set.

  As shown in FIG. 4, the fiber sheet 10 </ b> A obtained by the hot embossing has a large number of discrete dotted joints 4. The joint 4 is formed in a regular arrangement pattern. It is preferable that the joining part 4 is formed discontinuously, for example, in both the flow direction (MD) and the orthogonal direction (CD) of the fiber sheet 10A.

  The fiber sheet 10 </ b> A that has been subjected to the heat embossing in the weak bonding apparatus 25 is continuously sent to the stretching apparatus 30. As shown in FIGS. 2 to 5, the fiber sheet 10 </ b> A is drawn with a pair of concave and convex rolls 33 and 34 in which large-diameter portions 31 and 32 and small-diameter portions (not shown) are alternately formed in the axial direction. The apparatus 30 is stretched in a direction (CD) orthogonal to the transport direction (MD).

  The stretching device 30 is configured such that the pivotal support portions of one or both of the concave and convex rolls 33 and 34 are displaced up and down by a known lifting mechanism so that the distance between them can be adjusted. As shown in FIG. 1 and FIGS. 5 (b) and 5 (d), each concavo-convex roll 33, 34 has a large diameter portion 31 between one concavo-convex roll 33 and a large diameter portion 32 between the other concavo-convex roll 34. The large-diameter portion 32 of the other concave-convex roll 34 is assembled so as to be loosely inserted between the large-diameter portions 31 of the one concave-convex roll 33. The fiber sheet 10A is bitten between the rolls 33 and 34 in this state, and the fiber sheet 10A is stretched.

In this stretching step, as shown in FIGS. 4 and 5, the position of the joint portion 4 in the width direction of the fiber sheet 10 </ b> A and the positions of the large diameter portions 31 and 32 of the uneven rolls 33 and 34 are matched. Is preferred. Specifically, as shown in FIG. 4, the fiber sheet 10 </ b> A is formed with a plurality of rows of joint portions in which a plurality of joint portions 4 are formed in a straight line along the MD (see FIG. 4). FIG. 4 shows 10 rows), and in FIG. 4, one of the concave and convex portions is included in each of the joint portions 4 included in every other joint portion row R ₁ including the joint portion row R ₁ located on the leftmost side. position of the large diameter portion 31 of the roll 33 do not match, including the junction sequence R ₂ of the second from the left, for the joint portions included in each of the joint row R ₂ of every other therefrom, the other The position of the large diameter portion 32 of the uneven roll 34 is made to coincide. In FIG. 4, the range indicated by reference numerals 31 and 32 is the same as the peripheral surfaces of the large-diameter portions 31 and 32 of each roll at one point in a state where the fiber sheet 10 </ b> A is engaged between the two uneven rolls 33 and 34. The overlapping range is shown.

  When the fiber sheet 10A passes between the rolls 33 and 34 in a state of being bitten between the concave and convex rolls 33 and 34, as shown in FIGS. 5B and 5D, While the large-diameter portions 31 and 32 of any of the concave and convex rolls overlap, the region between the large-diameter portions that do not overlap with the large-diameter portions 31 and 32, that is, the region between the joint row R described above is positive in the width direction. To be stretched. Accordingly, it is possible to efficiently stretch the portion other than the joint portion of the fiber sheet 10A while preventing the joint portion 4 from being broken and the webs of the respective layers from being peeled off. Further, by this stretching, the non-elastic fiber webs 2 and 3 are sufficiently stretched, whereby the degree to which the non-elastic fiber webs 2 and 3 hinder free expansion and contraction of the elastic fiber web 1 is greatly reduced. As a result, according to this production method, it is possible to efficiently produce a stretchable nonwoven fabric that is highly stretchable and has a good appearance with little tearing and fuzzing.

  It is preferable that the peripheral surfaces of the large-diameter portions 31 and 32 of the uneven rolls 33 and 34 are not sharp so as not to damage the fiber sheet 10A. For example, as shown in FIGS. 5B and 5D, a flat surface having a predetermined width is preferable. The width W (see FIG. 5B) of the tip surfaces of the large diameter portions 31 and 32 is preferably 0.3 to 1 mm, and is 0.7 to 2 times the dimension of the joint portion 4 in the CD direction, in particular. It is preferably 0.9 to 1.3 times. Thereby, the fiber form of inelastic fiber becomes difficult to be destroyed, and a high-strength stretchable nonwoven fabric is obtained.

The pitch P between the large diameter portions (see FIG. 5B) is preferably 0.7 to 2.5 mm. The pitch P is preferably 1.2 to 5 times, particularly 2 to 3 times, the dimension of the joint portion 4 in the CD direction. As a result, a stretchable nonwoven fabric having a cloth-like appearance and a good touch can be obtained. The pitch of the CD direction of the joint 4 (junction sequence R ₁ together intervals adjacent in the CD direction or the joint row R ₂ distance between adjacent in the CD direction) is the pitch P between the large-diameter portion On the other hand, in order to match the positional relationship, it is basically doubled, but if the fiber sheet 10A is in the range of 1.6 times to 2.4 times due to elongation in the CD direction and neck-in, the positions are matched. It is possible.

  The fiber sheet 10A sent out from the stretching device 30 is released from the stretched state in the width direction. That is, the elongation is eased. As a result, the fiber sheet 10A exhibits elasticity and the sheet 10A contracts in the width direction. Thereby, the intended stretchable nonwoven fabric 10 is obtained. When the stretched state is released, the stretched state may be completely released, or the stretched state may be released in a state where the stretched state is maintained to some extent as long as stretchability is exhibited. Good.

  The present invention is not limited to the embodiment. For example, the stretchable nonwoven fabric 10 of the above-described embodiment has a configuration in which the same or different substantially inelastic non-elastic fiber layers 2 and 3 are laminated on both surfaces of the elastic fiber layer 1. Instead, a two-layer structure in which an inelastic fiber layer is laminated on one surface of the elastic fiber layer may be used. Or the form of the single layer structure which consists only of an elastic fiber layer may be sufficient. About the detail of the elastic nonwoven fabric of the form of these single layer or two-layer structure, the description regarding the elastic nonwoven fabric 10 of the said embodiment which concerns on a three-layer structure is applied suitably. In addition, when using a stretchable nonwoven fabric with a two-layer structure as a constituent material of an absorbent article, especially when used on a part that touches the user's skin, the non-elastic fiber layer is used to face the wearer's skin side. It is preferable from the viewpoints of touch and prevention of stickiness.

  Moreover, in the said embodiment, although the elastic fiber layer 1 and the nonelastic fiber layers 2 and 3 were joined by those whole surfaces, it replaces with this and the elastic fiber layer 1 and the nonelastic fiber layers 2 and 3 are partially You may join. Examples of means for partially joining the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 include, for example, thermal embossing, ultrasonic embossing, a partial spunlace method using a patterned water-permeable net, and needles arranged in a pattern. The partial needle punch method used, partial air through, etc. are mentioned. By these means, the elastic fiber layer 1 and the non-elastic fiber layers 2 and 3 can be joined intermittently or in a strip shape in an arbitrary pattern. Partial bonding is inferior in the sense of unity and bonding strength between the two fiber layers compared to full surface bonding. However, according to the partial bonding, the non-elastic fiber layers 2 and 3 are partially lifted from the elastic fiber layer 1, so that a stretchable nonwoven fabric with a three-dimensional feeling and thickness can be obtained.

  Moreover, when the nonwoven fabric of this invention is a structure formed by arranging an inelastic fiber layer on at least one surface of an elastic fiber layer, the structure of an elastic fiber layer and an inelastic fiber layer is not restrict | limited to what is shown in FIG.

  Further, in the method shown in FIG. 5, the fiber sheet 10 </ b> A is stretched without being sandwiched between the large diameter portion of one uneven roll and the small diameter portion of the other uneven roll. And it can also extend | stretch in the state which pinched | interposed the fiber sheet 10A between both. That is, it can be stretched in a state of bottoming through the fiber sheet. In addition, the stretching step can be performed by the method described in JP-A-6-133998.

  Moreover, in the said manufacturing method, although 10 A of fiber sheets were extended | stretched in CD direction, it can replace with this and can be extended in MD direction.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
The stretchable nonwoven fabric shown in FIG. 1 was manufactured using the apparatus shown in FIG. First, short fibers (core: PET, sheath: PE) having a diameter of 17 μm and a fiber length of 51 mm were supplied to a card machine to form an inelastic fiber web 3 ′ composed of a card web. The basis weight of the web 3 ′ was 10 g / m ² . The elastic fiber web 1 ′ was laminated on the non-elastic fiber web 3 ′.

The elastic fiber web 1 ′ was formed by the following method. As a polyolefin-based elastic resin mainly composed of propylene, a polyolefin-based elastomer having a propylene content of 85% by weight and an ethylene content of 15% by weight was used. This polyolefin-based elastomer was polymerized using a metallocene catalyst. As another elastic resin different from this, SEBS resin having a styrene content of 15% by weight, a weight average molecular weight of 100,000 and MFR of 30 g / 10 min (230 ° C., 2.16 kg) was used. These resins were melted using different extruders, the melted resin was extruded from a spinning nozzle at a die temperature of 290 ° C., and an elastic fiber web 1 ′ was formed on the net by a spinning blow method. The spinning nozzle was a side-by-side type, and a composite fiber composed of the two kinds of resins was spun. The fiber diameter of the elastic fiber was 25 μm. The basis weight of the fiber web 1 ′ was 40 g / m ² .

On the elastic fiber web 1 ′, a non-elastic fiber web 2 ′ made of the same short fibers as described above was laminated. The basis weight of the web 2 ′ was 10 g / m ² .

  The laminate of these three layers of web was introduced into a heat treatment machine, and hot air was blown by an air-through method to perform heat treatment. The heat treatment conditions were an on-net temperature of 140 ° C., a hot air flow rate of 2 m / second, a spraying pressure of 10 kPa, and a spraying time of 15 seconds. By this heat treatment, a fiber sheet 10B in which three layers of webs were integrated was obtained.

  Next, hot embossing was applied to the fiber sheet 10B. The hot embossing was performed using an embossing device provided with an embossed convex roll and a flat metal roll. As the embossed convex roll, a dot-shaped convex roll having a large number of convex portions having an MD pitch of 2 mm and a CD pitch of 2 mm was used. The temperature of each roll was 120 ° C., and the linear pressure was 300 N / cm. By this embossing, a fiber sheet 10A in which the joints were formed in a regular pattern was obtained.

The fiber sheet 10A was stretched. The stretching process was performed using a stretching apparatus including a pair of concave and convex rolls in which a large diameter portion and a small diameter portion were alternately formed in the axial length direction. The pitch P between the large diameter portions was 1.0 mm. The fiber sheet 10A was drawn into a CD by a drawing process. As a result, a nonwoven fabric having a basis weight of 60 g / m ² that expands and contracts to CD was obtained. In addition, the conveyance speed of each process was 10 m / min.

[Example 2]
The elastic fiber web 1 ′ was formed by the following method. As a polyolefin-based elastic resin mainly composed of propylene, a polyolefin-based elastomer having a propylene content of 85% by weight and an ethylene content of 15% by weight was used. This polyolefin-based elastomer was polymerized using a metallocene catalyst. As another inelastic resin different from this, a polypropylene resin (homo) of MFR 60 g / 10 min (230 ° C., 2.16 kg) was used. These resins were respectively extruded using different extruders, and the molten resin was extruded from a spinning nozzle at a die temperature of 290 ° C., and an elastic fiber web 1 ′ was formed on the net by a spinning blow method. As shown in FIG. 3, the spinning nozzle was a nozzle having a shape of extruding each resin alternately, and a mixed fiber of two kinds of resins. The weight ratio of polyolefin elastomer to polypropylene was 50/50. The fiber diameter of the elastic fiber was 25 μm. The fiber diameter of the inelastic fiber was 18 μm. The basis weight of the fiber web 1 ′ was 40 g / m ² .

  This web was introduced into a heat treatment machine, and hot air was blown by an air-through method to perform heat treatment. The heat treatment conditions were an on-net temperature of 140 ° C., a hot air flow rate of 2 m / second, a spraying pressure of 10 kPa, and a spraying time of 15 seconds. By this heat treatment, a fiber sheet 10B in which two types of fiber webs were integrated was obtained.

  Next, hot embossing was applied to the fiber sheet 10B. The hot embossing was performed using an embossing device provided with an embossed convex roll and a flat metal roll. As the embossed convex roll, a dot-shaped convex roll having a large number of convex portions having an MD pitch of 2 mm and a CD pitch of 2 mm was used. The temperature of each roll was 130 ° C., and the linear pressure was 300 N / cm. By this embossing, a fiber sheet 10A in which the joints were formed in a regular pattern was obtained.

The fiber sheet 10A was stretched. The stretching process was performed using a stretching apparatus including a pair of concave and convex rolls in which a large diameter portion and a small diameter portion were alternately formed in the axial length direction. The pitch P between the large diameter portions was 1.0 mm. The fiber sheet 10A was drawn into a CD by a drawing process. As a result, a nonwoven fabric having a basis weight of 40 g / m ² that expands and contracts to CD was obtained. In addition, the conveyance speed of each process was 10 m / min.

[Comparative Example 1]
An SEBS resin having a styrene content of 15% by weight, a weight average molecular weight of 100,000 and MFR30 was used as the elastic resin. Using this elastic resin, an elastic fiber web was molded at a die temperature of 290 ° C. The diameter of the elastic fiber was 32 μm. A stretchable nonwoven fabric was prepared in the same manner as in Example 1 except for these.

[Evaluation]
The properties of the stretchable nonwoven fabric obtained in the examples and comparative examples are shown in Table 1 below. The measurement method for each item in the table is as follows.

<Strength, elongation and residual strain>
A rectangular test piece having a size of 50 mm in the stretching direction of the stretchable nonwoven fabric and 25 mm in the direction perpendicular thereto was cut out. The test piece was attached to Orientec Tensilon RTC1210A. The distance between chucks was 25 mm. The test piece was stretched at a speed of 300 mm / min in the stretching direction of the nonwoven fabric, and the load at that time was measured. The load at the maximum point at that time was defined as the maximum strength. Moreover, when the length of the test piece at that time was set to B and the length of the original test piece was set to A, {(BA) / A} * 100 was made into the maximum elongation (%). Further, a 100% elongation cycle test was performed, and the strength at 100% elongation was determined from the load at 100% elongation. Furthermore, after 100% elongation, the ratio of the length that did not return when returning to the origin at the same speed was measured, and the value was defined as the residual strain.

<Jointness between elastic fiber layer and non-elastic fiber layer>
The state when peeled by hand so as to peel between the elastic fiber layer and the non-elastic fiber layer was determined according to the following criteria. Easily peels off: x, feels a little resistant: Δ, part of the layer does not peel and part remains in the other layer: ○, part of the layer does not peel off and most remains in the other layer: ◎. Judgment was made by three people, and if two or more people had the same opinion, the opinion was taken, and if three people were different opinions, the middle opinion was taken as the judgment result.

  As is clear from the results shown in Table 1, the non-woven fabric of the example has higher strength than the non-woven fabric of the comparative example, while maintaining the maximum elongation and residual strain at the same level as the non-woven fabric of the comparative example. Further, it can be seen that the bonding property between the elastic fiber layer and the non-elastic fiber layer is good. When a disposable diaper was prepared using the nonwoven fabric of the example for the exterior, this diaper was soft to the touch, highly breathable, easy to stretch enough to be stretched, and had the characteristics that it was difficult to stick rubber marks because it was tightened over the entire surface. .

[Examples 3 to 6]
Using the resins shown in Table 2, a stretchable nonwoven fabric was obtained in the same manner as in Example 1. The basis weight of the elastic fiber web 1 ′ was 30 g / m ² .

Example 7
Using the resin shown in Table 2, a stretchable nonwoven fabric was obtained in the same manner as in Example 7. The basis weight of the fiber web 1 ′ was 40 g / m ² .

[Evaluation]
About the elastic nonwoven fabric obtained in Examples 3-7, evaluation similar to Example 1 was performed. Further, the strength at 50% elongation was measured by the following method. The results are shown in Table 2.

<Strength at 50% elongation>
After measuring the 100% elongation strength of the stretchable nonwoven fabric by the method described above, the nonwoven fabric was shrunk to a 50% stretched state. The strength at this time was defined as strength at 50% elongation. The technical significance of the strength at 50% elongation is as follows. When putting on a diaper, it is usual to put the diaper in a state where the waist portion of the diaper is stretched to about 100% and then contracted and stretched by about 50%. Therefore, when considering the case where the stretchable nonwoven fabric of the present invention is used for the waist portion of the diaper, the higher the strength at 50% elongation, the harder the diaper that is attached slips down.

  As is apparent from the results shown in Table 2, it can be seen that the stretchable nonwoven fabric of each example has high maximum elongation and residual strain, and further high strength. Among the elastic nonwoven fabrics of each example, it can be seen that the elastic nonwoven fabric of Example 4 has a particularly high strength at 50% elongation.

Drawing 1 is a mimetic diagram showing the section structure of one embodiment of the elastic nonwoven fabric of the present invention. FIG. 2 is a schematic view showing a preferred apparatus used for producing the stretchable nonwoven fabric shown in FIG. FIG. 3 is a schematic view showing an example of the structure of a spinning die of a spinning blown spinning device which is a second web forming device in the device shown in FIG. FIG. 4 is a plan view showing an example of a fiber sheet to be stretched. 5A is a cross-sectional view taken along the line aa in the CD direction of the fiber sheet shown in FIG. 4, and FIG. 5B is a diagram of a deformed state (stretched state) between the concavo-convex rolls. Sectional drawing corresponding to (a), FIG.5 (c) is sectional drawing in alignment with the cc line of CD direction of the fiber sheet shown in FIG.4, FIG.5 (d) is the state deform | transformed between the uneven | corrugated rolls ( It is sectional drawing equivalent to FIG.5 (c) of the state extended | stretched.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Elastic fiber layer 2 Inelastic fiber layer 3 Inelastic fiber layer 4 Joining part 10A Fiber sheet 10 Elastic nonwoven fabric

Claims (6)

An elastic fiber layer containing an elastic fiber containing a polyolefin-based elastomer mainly composed of propylene, and another elastic fiber or non-elastic fiber different from the elastic fiber;
The polyolefin elastomer is a stretchable nonwoven fabric having a propylene content of 80 to 90% by weight and a density of 0.855 to 0.880 g / cm ³ .   The stretchable nonwoven fabric according to claim 1, wherein the polyolefin-based elastomer is polymerized using a metallocene catalyst.   The elastic nonwoven fabric according to claim 1 or 2, wherein the polyolefin-based elastomer has a heat of fusion value A of 2 to 20 mJ / mg and a heat of fusion value B of 12 to 24 mJ / mg.   The stretchable nonwoven fabric according to any one of claims 1 to 3, wherein the polyolefin elastomer has a melt flow rate (MFR) of 2 to 350 g / 10 min.   The elastic nonwoven fabric according to any one of claims 1 to 4, wherein the elastic fiber containing the polyolefin-based elastomer consists of the polyolefin-based elastomer alone or contains the polyolefin-based elastomer and other thermoplastic elastomers. .   The stretchable nonwoven fabric according to any one of claims 1 to 5, wherein a substantially inelastic nonelastic fiber layer is disposed on at least one surface of the elastic fiber layer.

Images