JP5203349B2 - Non-woven - Google Patents

Description

  The present invention relates to a nonwoven fabric containing heat-extensible fibers whose length is extended by heating. The nonwoven fabric of the present invention is particularly suitably used as a constituent material for various absorbent articles such as sanitary napkins and disposable diapers.

  Regarding a nonwoven fabric made from a heat-extensible fiber, which is a fiber whose length is increased by heating, the applicant previously has a number of pressure-bonded portions to which constituent fibers are pressure-bonded or bonded, and other than pressure-bonded portions. The three-dimensional structure in which the intersections of the constituent fibers are joined by means other than pressure bonding, and the pressure bonding portion is a concave portion and the concave portion is a convex portion between at least one surface. A shaped nonwoven fabric was proposed (see Patent Document 1). This nonwoven fabric has the advantage that it has a three-dimensional uneven shape, is flexible, and has a low basis weight, without using a special manufacturing method, by using heat-extensible fibers as a raw material.

  As a result of further studies by the present inventors on the nonwoven fabric made from heat-extensible fibers, the heat-extensible fibers are heated in the step of manufacturing the nonwoven fabric or the post-processing step when incorporating the nonwoven fabric into the absorbent article. It became clear that fuzzing was likely to occur by stretching. It has also been found that the heat-extensible fibers have a Young's modulus lower than that of ordinary heat-fusible fibers, which tends to reduce the bulk when a load is applied to the nonwoven fabric in the thickness direction.

  Regarding the fluffing of the nonwoven fabric, Patent Document 2 describes that as a top sheet in a disposable diaper, one formed of a nonwoven fabric processed so that the fiber tip of the surface that touches the skin does not fluff is described. As a means for preventing the fiber tip of the surface in contact with the skin from becoming fluffy, a method of applying pressure with a roller to the surface of the nonwoven fabric that contacts the skin is used. According to this means, when a pressure is applied to the nonwoven fabric with a roller, the fibers on the nonwoven fabric surface can be pressed against the nonwoven fabric surface to be in a twisted state, and the nonwoven fabric surface becomes smooth. ing. However, the bulk of the nonwoven fabric is reduced by the pressure of the roller.

JP 2005-350836 A JP 2003-265528 A

  The subject of this invention exists in improvement of the nonwoven fabric containing a heat | fever extensible fiber.

The present invention includes a non-woven fabric having heat-extensible fibers whose length is increased by heating and having a large number of convex portions and concave portions on one surface side, and the heat-extensible fibers constituting the convex portions are The thermal elongation rate is higher in the lower part than in the upper part of the convex part,
As the raw fiber of the heat-extensible fiber, two or more types of heat-extensible raw material fibers having different temperatures at which thermal extension is started are used.
The upper side of the convex part is formed using a low-temperature heat-extensible raw fiber that starts thermal elongation at a relatively low temperature, and the lower part of the convex part is a high-temperature heat-extensible raw fiber that starts thermal extension at a relatively high temperature. The nonwoven fabric currently formed using is provided.

In addition, the present invention provides a preferable method for producing the nonwoven fabric as described above.
Heat is applied to a web having a layer containing a low-temperature heat-extensible raw material fiber that starts thermal elongation at a relatively low temperature on a layer containing a high-temperature heat-extensible raw material fiber that starts heat extension at a relatively high temperature. Consolidate with or without it to form multiple joints,
Next, hot air is blown from the side of the layer containing the low-temperature heat-extensible raw fiber that starts thermal expansion at a relatively low temperature, and both the heat-extensible raw fibers between the joints are heat-extended to form a large number of convex portions and concave portions. A method for producing a nonwoven fabric, comprising:
The present invention provides a method for producing a nonwoven fabric in which the blowing of hot air is completed before the two heat-extensible raw fibers are completely heated.

  In the nonwoven fabric of the present invention, since the fibers located on the surface side are not easily stretched, when the nonwoven fabric is subjected to post-processing for bulk recovery such as blowing hot air, the surface side is less likely to fluff. In addition, since the fiber located on the back side is easily stretched by heat, when the nonwoven fabric is subjected to post-processing for bulk recovery such as blowing hot air, the fiber on the back side is thermally stretched and the bulk recovery property is good. become.

Fig.1 (a) is a perspective view which shows one Embodiment of the nonwoven fabric of this invention, FIG.1 (b) is a principal part enlarged view of the longitudinal cross-section of the nonwoven fabric shown to Fig.1 (a). FIG. 2 is a schematic view showing an apparatus suitably used for producing the nonwoven fabric shown in FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The perspective view of one Embodiment of the nonwoven fabric of this invention is shown by Fig.1 (a). Moreover, the principal part enlarged view of the longitudinal cross-section of the nonwoven fabric shown to Fig.1 (a) is shown by FIG.1 (b). The nonwoven fabric 10 of this embodiment has a multilayer structure. One side of the nonwoven fabric 10 (the back surface 10b in FIG. 1B) is substantially flat, and the other side (the front surface 10a in FIG. 1B) has a concavo-convex shape having a large number of convex portions 19 and concave portions 18. ing. That is, it is three-dimensionally shaped. The concave portion 18 includes a joint portion formed by compacting and joining the constituent fibers of the nonwoven fabric 10. Examples of means for forming the joint include embossing with or without heat, ultrasonic embossing, and the like. On the other hand, the convex part 19 is a non-joining part. The thickness of the concave portion 18 is smaller than the thickness of the convex portion 19. The convex portion 19 has a shape protruding toward the surface side of the nonwoven fabric 10 (upper surface side in FIG. 1B). The inside of the convex portion 19 is filled with the constituent fibers of the nonwoven fabric 10. In the convex part 19, the heat | fever extensible fibers which are the constituent fibers of the nonwoven fabric 10 are fuse | melted in those intersections. Since the heat-extensible fibers are thermally bonded to each other at the convex portion 19, fuzz on the surface of the nonwoven fabric 10 is less likely to occur. Whether or not the fibers are thermally fused is determined by observing the nonwoven fabric 10 with a scanning electron microscope.

  The recessed part 18 has the 1st linear part 18a extended in one direction in parallel with each other. Moreover, the recessed part 18 has the 2nd linear part 18b extended in one direction in parallel so that it may cross | intersect a 1st linear part. A closed rhombus is formed by intersecting the two linear portions 18a and 18b. This rhombus portion is a convex portion 19. That is, the convex portion 19 is formed to be surrounded by a continuous closed concave portion 18.

The area ratio between the concave portion 18 and the convex portion 19 in the nonwoven fabric 10 is expressed by an embossing rate (an embossed area ratio, that is, a ratio of the total area of the concave portion 18 to the entire nonwoven fabric 10), and affects the bulkiness and strength of the nonwoven fabric 10. give. From these viewpoints, the embossing rate in the nonwoven fabric 10 is preferably 5 to 35%, particularly preferably 10 to 25%. The embossing rate is measured by the following method. First, a surface enlarged photograph of the nonwoven fabric 10 is obtained using a microscope (manufactured by Keyence Co., Ltd., VHX-900), the scale is adjusted to this surface enlarged photograph, and the dimension of the recess 18 (that is, the embossed portion) is measured. The total area P of the recesses 18 in the entire area Q is calculated.
The embossing rate can be calculated by the formula (P / Q) × 100.

  The nonwoven fabric 10 includes, as its constituent fibers, heat-extensible fibers that are fibers whose length is increased by heating. As the heat-extensible fiber, for example, a fiber in which the crystal state of the resin is changed by heating and stretched can be mentioned. The heat-extensible fibers are present in the nonwoven fabric 10 in a state that can be extended by heating. Therefore, when the nonwoven fabric 10 is heated, the heat-extensible fibers contained therein are stretched, and the nonwoven fabric 10 is more bulky than before heating.

  The heat-extensible fiber particularly preferably used in the nonwoven fabric 10 includes a first resin component made of a high melting point resin and a melting point lower than the melting point of the first resin component (in the case of a resin having no melting point described later, a softening point). And a second resin component made of a low-melting-point resin having a substitute, and the second resin component is a composite fiber in which at least a part of the fiber surface is continuously present in the length direction (hereinafter, this fiber is referred to as “ It is referred to as “heat-extensible composite fiber”. The 1st resin component in a heat | fever extensible composite fiber is a component which expresses the heat | fever extensibility of this fiber, and a 2nd resin component is a component which expresses heat-fusibility. Details of the heat-extensible composite fiber will be described later.

  In each convex part 19 of the nonwoven fabric 10, there is a difference in the thermal expansion rate between the heat-extensible fibers located at the upper part 19a of the convex part 19 and the heat-extensible fibers located at the lower part 19b. The present invention has one of the features in this respect. Specifically, when compared at the same heating temperature, the heat-extensible fibers constituting the convex portion 19 have a thermal elongation rate of the one located in the lower portion 19b rather than the one located in the upper portion 19a of the convex portion 19. It is relatively high. That is, when heat at a certain temperature is applied, the fiber located at the lower portion 19b of the convex portion 10 has a greater degree of thermal expansion than the fiber located at the upper portion 19a. In other words, the fiber located in the upper part 19a of the convex portion 10 has a smaller degree of thermal expansion than the fiber located in the lower part 19b. Since the degree of thermal elongation of the heat-extensible fibers contained in the convex portion 19 is such, the nonwoven fabric 10 is difficult to thermally stretch the fibers located in the upper portion 19a. When subjected to post-processing for bulk recovery, there is an advantageous effect that the surface of the upper portion 19a is less likely to fluff. Moreover, since the fiber located in the lower part 19b is easy to heat-extend, when the nonwoven fabric 10 is subjected to post-processing for bulk recovery such as blowing hot air, the fiber on the lower part 19b side is thermally stretched, and the bulk recoverability is improved. There is also an advantageous effect of being good. Bulk recovery by blowing hot air onto the nonwoven fabric 10 will be described later.

  The thermal elongation rate of the heat-extensible fibers contained in the convex portion 19 may be gradually increased from the upper portion 19a toward the lower portion 19b, or may be increased in a step shape. In the present invention, there is no clear boundary between the upper part 19 a and the lower part 19 b of the convex part 19, and the “upper part 19 a” and “lower part 19 b” in the thickness direction of the nonwoven fabric 10 are relative to each other in the convex part 19. This indicates a general positional relationship.

  From the viewpoint of making the above-described effect more prominent, at the temperature of the melting point of the low melting point resin constituting the heat-extensible fiber positioned above the convex portion + 20 ° C. (in the case of a resin having no melting point, the softening point + 20 ° C. The thermal elongation rate of the heat stretchable fiber located at the upper portion 19a of the convex portion 19 is 0.1% or more and less than 3.0%, particularly 0.1% or more and less than 2.5%, especially 0 It is preferably 5% or more and less than 2.5%. On the other hand, the thermal elongation rate of the heat-extensible fiber located at the lower portion 19b of the convex portion 19 is 3.0% or more and less than 20%, particularly 3.5% or more and less than 10.5%, especially at the above temperature. It is preferable that it is 4.0% or more and less than 10%. This thermal elongation rate is measured for the heat-extensible fibers contained in the convex portion 19. A method for measuring the thermal elongation rate will be described later.

  The melting points of the first resin component and the second resin component are measured using a differential scanning calorimeter (DSC6200 manufactured by Seiko Instruments Inc.). A finely cut fiber sample (sample weight 2 mg) is subjected to thermal analysis at a heating rate of 10 ° C./min, and the melting peak temperature of each resin is measured. The melting point is defined by its melting peak temperature. When the melting point of the second resin component cannot be clearly measured by this method, this resin is defined as “resin having no melting point”. In this case, the temperature at which the second resin component is fused is defined as the softening point as the temperature at which the second resin component begins to flow.

  As a fiber used as the raw material of the nonwoven fabric 10, a heat-extensible fiber is used. In the following description, for the purpose of distinguishing between the heat-extensible fibers contained in the nonwoven fabric 10 and the heat-extensible fibers that are the raw material of the nonwoven fabric 10, the heat-extensible fibers that are the raw material of the nonwoven fabric 10 are referred to as “ It is called “heat-extensible raw fiber”. When simply referred to as “heat-extensible fiber”, it refers to a heat-extensible fiber contained in the nonwoven fabric 10. As the heat-extensible raw fiber, two kinds of fibers having different temperatures at which heat extension is started are used. That is, a heat-extensible raw fiber that starts thermal expansion at a relatively low temperature (hereinafter referred to as “low-temperature heat-extensible raw fiber”) and a heat-extensible raw fiber that starts thermal expansion at a relatively high temperature (hereinafter referred to as “low-temperature heat-extensible raw fiber”) , Referred to as “high-temperature heat-extensible raw fiber”). In the nonwoven fabric 10 manufactured using such two kinds of fibers, the upper portion 19a side of the convex portion 19 is formed using a low-temperature heat-extensible raw fiber, and the lower portion 19b side of the convex portion 19 is a high-temperature heat-extensible raw material fiber. It is formed using. The preferable manufacturing method of the nonwoven fabric 10 using a heat | fever extensible raw fiber is mentioned later.

  When the above-mentioned two types of heat-extensible raw fiber are used, the blending ratio (weight) of the two is low-temperature heat-extensible raw fiber: high-temperature heat-extensible raw fiber = 95: 5 to 5:95, particularly 80:20 to It is preferably 20:80, further 60:40 to 40:60, and more preferably 55:45 to 45:55.

  The heat-extensible raw fiber (low-temperature heat-extensible raw fiber and high-temperature heat-extensible raw fiber) particularly preferably used in the nonwoven fabric 10 includes a first resin component made of a high-melting resin and a melting point lower than the melting point of the first resin component. Or a second fiber component composed of a low-melting point resin having a softening point, and the second resin component is continuously present in the length direction on at least a part of the fiber surface (hereinafter, this fiber is referred to as “ It is referred to as “heat-extensible composite raw fiber”. The 1st resin component in a heat | fever extensible composite raw material fiber is a component which expresses the heat | fever extensibility of this fiber, and a 2nd resin component is a component which expresses heat-fusibility.

  The heat-extensible composite raw fiber can be stretched by heat at a temperature lower than the melting point of the first resin component. The heat-stretchable composite raw fiber has a temperature that is 10 ° C higher than the melting point of the second resin component, and in the case of a resin that does not have a melting point, the thermal elongation rate at a temperature 10 ° C higher than the softening point is 0.5 to 20%, It is preferably 3 to 20%, particularly 5 to 20%. The nonwoven fabric 10 manufactured using such a fiber having a thermal elongation rate as a raw material becomes bulky or exhibits a three-dimensional appearance due to thermal expansion of the fiber in the manufacturing process of the nonwoven fabric 10. For example, the uneven shape on the surface of the nonwoven fabric 10 becomes remarkable.

The thermal elongation rate of the raw fiber is measured by the following method. A thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc. is used. As a sample, after preparing a plurality of fibers having a length of 10 mm or more collected so that the total weight per fiber length of 10 mm is 0.5 mg, and arranging the plurality of fibers in parallel, Mount on the device with 10mm distance between chucks. The measurement start temperature is 25 ° C., and the temperature is increased at a temperature increase rate of 5 ° C./min with a constant load of 0.73 mN / dtex applied. The amount of elongation of the fiber at that time is measured, and in the case of a resin having no melting point at a temperature 10 ° C. higher than the melting point of the second resin component, the elongation amount Xmm at a temperature 10 ° C. higher than the softening point is read.
The thermal elongation rate of the raw fiber is calculated from (X / 10) × 100 [%].
In addition, the temperature at which the thermal expansion of the raw fiber starts is set to a temperature at which the thermal expansion rate of the raw fiber calculated by the above equation becomes 1%.

  There is no restriction | limiting in particular in the kind of 1st resin component and 2nd resin component, What is necessary is just resin with fiber formation ability. In particular, the difference in melting point between the two resin components, or the difference between the melting point of the first resin component and the softening point of the second resin component is 20 ° C. or more, particularly 25 ° C. or more. It is preferable because it can be easily performed. When the heat-extensible composite raw fiber is a core-sheath type, a resin having a melting point of the core component higher than the melting point or softening point of the sheath component is used. In particular, it is preferable to use a core-sheath type heat-extensible composite raw material fiber having polypropylene (PP) or polyethylene terephthalate (PET) as a core and a resin having a melting point lower than these as a sheath. As a preferable combination of the first resin component and the second resin component, as the second resin component when the first resin component is PP, the high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear Examples thereof include polyethylene (PE) such as low density polyethylene (LLDPE), ethylene propylene copolymer, and polystyrene. In addition, when a polyester resin such as PET or polybutylene terephthalate (PBT) is used as the first resin component, in addition to the example of the second resin component described above, PP, copolymer polyester, etc. may be used as the second resin component. Can be mentioned. Furthermore, examples of the first resin component include polyamide-based polymers and two or more types of copolymers of the first resin component described above, and examples of the second resin component include two or more types of the second resin component described above. Copolymers are also included. These are appropriately combined.

  In particular, the upper portion 19a side of the convex portion 19 of the nonwoven fabric 10 includes a core-sheath type thermally stretchable conjugate fiber in which the first resin component is polypropylene and the second resin component is polyethylene, and hot air is blown to the nonwoven fabric 10. It is preferable from the point that the fluffing on the surface 10a can be effectively prevented and the bulk recovery of the nonwoven fabric 10 can be made more remarkable. For the same reason, it is preferable that the lower portion 19b side of the convex portion 19 includes a core-sheath type heat-stretchable conjugate fiber in which the core is polyethylene terephthalate and the sheath is polyethylene.

  As the fiber length of the heat-extensible raw material fiber, an appropriate length is used according to the method for manufacturing the nonwoven fabric 10. For example, when the nonwoven fabric 10 is manufactured by a card method as described later, the fiber length is preferably about 30 to 70 mm.

  The fiber diameter of the heat-extensible raw fiber is reduced by heat extension. Therefore, the heat-extensible fiber contained in the nonwoven fabric 10 generally has a fiber diameter smaller than the fiber diameter of the heat-extensible raw material fiber that is the raw material. The fiber diameter of the heat-extensible fiber contained in the nonwoven fabric 10 is appropriately selected according to the specific use of the nonwoven fabric 10. When the nonwoven fabric 10 is used as a constituent member of an absorbent article such as a surface sheet of the absorbent article, the fiber diameter of the heat-extensible fibers contained in the nonwoven fabric 10 is 10 to 35 μm, particularly 15 to 30 μm, especially 15 to 25 μm. It is preferable. The fiber diameter of the heat-extensible raw fiber is determined in consideration of the fiber diameter of the heat-extensible fiber contained in the nonwoven fabric 10.

  As a result of the examination by the present inventors, it has been found that the heat-extensible raw fiber has a lower Young's modulus than a fiber made of a normal fiber-forming resin (a fiber that does not thermally stretch or heat shrinks). Therefore, in the manufacturing process of the nonwoven fabric 10, when heated by hot air treatment or the like, the fibers do not stand up together with the thermal extension, and thus the nonwoven fabric 10 hardly flies. Furthermore, a low Young's modulus means that the fiber itself is soft. The softness of the fibers also contributes to the improvement of the touch of the nonwoven fabric 10 and brings a good texture to the nonwoven fabric 10. In the nonwoven fabric 10, it is more preferable in terms of fluff and texture that the upper 19 a side of the convex portion 19 of the nonwoven fabric 10 has a lower Young's modulus than the lower portion 19 b side of the convex portion 19.

  From the above viewpoint, it is preferable that the heat-extensible raw material fiber used for the nonwoven fabric 10 has a Young's modulus of 0.2 to 1 GPa, particularly 0.4 to 0.8 GPa. In order to set the Young's modulus within this range, the stretching conditions for producing the heat-extensible fibers (lowering the draw ratio), the type of resin constituting the heat-extensible fibers, the amount of resin blended (two-component system) In the case of fibers) etc. may be adjusted appropriately. Young's modulus is measured by the following method.

[Young's modulus measurement method]
A thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc. is used. The measurement environment temperature is 25 ° C. As a sample, after preparing a plurality of fibers having a length of 10 mm or more collected so that the total weight per fiber length of 10 mm is 0.5 mg, and arranging the plurality of fibers in parallel, The chuck is mounted at a distance of 10 mm, and a constant load of 0.73 mN / dtex is applied. Then, after obtaining a stress-strain curve under the condition of 240 mN / min, the slope of the tangent of the curve when the strain is 0.1% is defined as the Young's modulus.

  Examples of the heat-extensible raw fiber include Japanese Patent No. 4131852, Japanese Patent Application Laid-Open No. 2005-350836, Japanese Patent Application Laid-Open No. 2007-303035, Japanese Patent Application Laid-Open No. 2007-204899, Japanese Patent Application Laid-Open No. 2007-204901, and Japanese Patent Application Laid-Open No. 2007. -204902, Unexamined-Japanese-Patent No. 2008-101285, etc. can use the fiber.

  The non-woven fabric 10 may be composed only of heat-extensible fibers, or contains other fibers, for example, two components having different melting points, in addition to the heat-extensible fibers, and is a non-heat-extensible core formed by stretching. The sheath-type heat-fusible conjugate fiber may be included. In addition, fibers that do not inherently have heat-fusibility (for example, natural fibers such as cotton and pulp, rayon, and acetate fibers) may additionally be included. When the nonwoven fabric 10 includes other fibers in addition to the heat-extensible fibers, the proportion of the heat-extensible fibers in the nonwoven fabric 10 is preferably 30% by weight or more, particularly preferably 50% by weight or more. The fiber ratio is preferably 70% by weight or less, particularly preferably 50% by weight or less.

Nonwoven 10, which if used for example as a topsheet of an absorbent article, the basis weight of 10 to 80 g / m ^2, especially 15 to 60 g / m ^2, it is preferable in particular 20 to 40 g / m ² . When using for the same use, it is preferable that the thickness of the nonwoven fabric 10 is 0.5-3, especially 0.7-3 mm in the state after hot air recovery. The thickness of the nonwoven fabric was measured by the method described later.

  Next, the suitable manufacturing method of the nonwoven fabric 10 is demonstrated, referring FIG. The apparatus 20 shown in FIG. 2 includes a web manufacturing unit 30, an embossing unit 40, and a hot air blowing unit 50. In the web manufacturing unit 30, the web 10a is manufactured using heat-extensible raw fiber. As the heat-extensible raw fiber, a composite fiber containing the first resin component and the second resin component described above is used.

  As the web manufacturing unit 30, for example, two card machines 31a and 31b as shown in the figure can be used. Depending on the specific application of the nonwoven fabric 10, another web manufacturing apparatus such as an airlaid apparatus can be used instead of the card machine. The card machine 31a is supplied with a low-temperature heat-extensible raw fiber. The card machine 31b is supplied with high-temperature heat-extensible raw fiber. The webs formed by the respective card machines are laminated to form a web 10a. In the web 10a, the low-temperature heat-extensible raw fiber is located in the upper layer, and the high-temperature heat-extensible raw fiber is located in the lower layer. In the following description, in the web 10a, the surface on the side where the low-temperature heat-extensible raw fiber is present is referred to as the first surface 101, and the surface on the side where the high-temperature heat-extensible raw fiber is present is referred to as the second surface 102. I will call it. The first surface 101 is a surface that comes into contact with the pattern roll 41 in the embossing unit 40 to be described later, and is a surface to which hot air is blown in the hot air blowing unit 50. The 2nd surface 102 is a surface which contacts the flat roll 42 in the embossing part 40, and is a surface which opposes the conveyor belt 52 which consists of a breathable net in the hot air spraying part 50 mentioned later.

  The web 10a manufactured in the web manufacturing unit 30 is sent to the embossing unit 40 to become the embossed web 10b. The embossing unit 40 includes a pair of rolls 41 and 42. The roll 41 is made of a metal pattern roll having a large number of irregularities formed on its peripheral surface. The uneven pattern in the pattern roll can be appropriately selected according to the specific use of the nonwoven fabric 10. For example, when forming the rhombus lattice-shaped emboss pattern shown in FIG. 1, convex portions having a shape corresponding to the rhombus lattice may be formed on the peripheral surface of the roll 41. In addition, when it is desired to form a dot-like emboss pattern (not shown) on the nonwoven fabric 10, a convex portion having a shape corresponding to the dot may be formed on the peripheral surface of the roll 41. On the other hand, the roll 42 is a flat roll having a smooth peripheral surface. The roll 42 is made of metal, rubber, paper, or the like.

  In the embossing part 40, the web 10a is pinched by both rolls 41 and 42 to perform embossing. Specifically, the heat-extensible fibers, which are constituent fibers of the web 10a, are consolidated by consolidation with or without heat to form joints composed of a large number of embossed portions on the web 10a. 10b is manufactured. In this manufacturing method, the roll 41 and the roll 42 have a heatable structure. During the operation of the embossing section 40, it is preferable that the pattern roll 41 and / or the flat roll 42 are heated to a predetermined temperature.

  When at least one of the pattern roll 41 and the flat roll 42 is heated in the embossed portion 40, the heating temperature is the melting point of the second resin component of the low-temperature heat-extensible raw fiber −20 ° C. or more and the first resin component The temperature is preferably lower than the melting point.

  The embossed web 10 b processed by the embossing unit 40 is then conveyed to the hot air blowing unit 50. The hot air blowing unit 50 includes a hood 51. The embossed web 10 b passes through the hood 51. Moreover, the hot air spraying part 50 is provided with the conveyor belt 52 which consists of a breathable net. The conveyor belt 52 circulates in the hood 51. The embossed web 10b is placed on the conveyor belt 52 and conveyed in the hot air blowing unit 50. The conveyor belt 52 is made of metal or resin such as polyamide and polyester.

  In the hot air blowing unit 50, hot air is blown against the embossed web 10b by an air-through method. That is, the hot air blowing unit 50 is configured such that hot air heated to a predetermined temperature penetrates the embossed web 10b. The air-through process is performed at a temperature at which the heat-extensible raw fiber in the embossed web 10b is elongated by heating. And it is performed at the temperature at which the intersections of the free stretchable raw fiber existing in portions other than the embossed portion of the embossed web 10b are heat-sealed.

  The temperature of the hot air is a temperature at which both the low-temperature heat-extensible raw fiber and the high-temperature heat-extensible raw fiber are thermally extended. Further, the temperature is set such that the low-temperature heat-extensible raw fibers are fused and the high-temperature heat-extensible raw fibers are fused. Specifically, the temperature of the hot air is preferably not lower than the melting point of the second resin component of the low-temperature heat-extensible raw fiber + 5 ° C. and not higher than the melting point of the first resin component. In particular, the melting point of the second resin component + 10 ° C. or higher and the melting point of the first resin component−10 ° C. or lower are preferable from the viewpoint of strength and texture. By blowing hot air at this temperature, the low-temperature heat-extensible raw fiber and the high-temperature heat-extensible raw fiber are thermally extended. Since a part of the low-temperature heat-extensible raw fiber and the high-temperature heat-extensible raw fiber are fixed by the embossed portions, the portions that are thermally stretched are the portions between the embossed portions. And since the low-temperature heat-extensible raw material fiber and the high-temperature heat-extensible raw material fiber are partially fixed by the embossed portion, the elongation of the heat-extended fiber loses its place in the plane direction of the embossed web 10b. And move in the thickness direction of the embossed web 10b. Thereby, the convex part 19 is formed between embossed parts, and the nonwoven fabric 10 becomes bulky. Moreover, it comes to have the three-dimensional appearance in which many convex parts 19 were formed. Furthermore, the low-temperature heat-extensible raw material fiber and the high-temperature heat-extensible raw material fiber are bonded to each other or to each other by fusion.

  The blowing of hot air in the present production method is terminated before the heat-extensible raw fiber is completely heated. Thereby, the nonwoven fabric containing the heat | fever extensible fiber which can be extended | stretched by the subsequent heat processing process is obtained. This non-woven fabric is the non-woven fabric 10 intended in the present invention. Therefore, the nonwoven fabric 10 is manufactured using a heat | fever extensible raw fiber, and contains a heat | fever extensible fiber.

  In hot air blowing, the degree of thermal elongation of the low-temperature heat-extensible raw fiber is larger than that of the high-temperature heat-extensible raw fiber by the lower temperature at which thermal elongation starts. As a result, when the heat treatment is further performed, the low-temperature heat-extensible raw fiber has a relatively low thermal elongation rate because the thermal elongation elongation is smaller. In other words, the high-temperature heat-extensible raw fiber has a relatively small degree of heat extension due to heat treatment. As a result, when the heat treatment is further performed, the high-temperature heat-extensible raw fiber has a relatively high thermal elongation rate because the thermal elongation elongation is larger. Moreover, since the high-temperature heat-extensible raw fiber is present at a position away from the first surface 101, which is the hot air blowing surface, the degree of thermal extension due to the hot air blowing is smaller than that of the low-temperature heat-extensible raw fiber, This also increases the degree of further thermal extension after thermal extension. For these reasons, in the obtained nonwoven fabric 10, the heat-extensible fiber constituting the convex portion 19 has a thermal elongation rate measured at the same temperature in the lower portion 19 b rather than the upper portion 19 a of the convex portion 19. Get higher.

  The nonwoven fabric 10 obtained in this way can be applied to various fields that make use of its uneven shape, bulkiness and high strength. For example, surface sheets in the field of disposable hygiene articles such as disposable diapers and sanitary napkins, second sheets (sheets disposed between the surface sheet and the absorber), back sheets, leak-proof sheets, or personal wipes, It is suitably used as a skin care sheet, and further as an objective wiper. When using the nonwoven fabric 10 for absorbent articles, such as a sanitary napkin, for example, it can distribute | arrange on an absorber so that the surface which has a convex part and a recessed part in this nonwoven fabric 10 may face a wearer's skin.

  The nonwoven fabric 10 in a state before being used in these applications is generally stored in a state of being wound in a roll shape. Due to this, the bulk of the nonwoven fabric 10 is often reduced. Therefore, when the nonwoven fabric 10 is used, hot air is blown onto the nonwoven fabric 10 by an air-through method to recover the reduced bulk. preferable. In restoring the bulk, it is preferable to use hot air having a temperature lower than the melting point of the second resin component in the low-temperature heat-extensible raw fiber and at a temperature equal to or higher than the melting point −50 ° C. as the hot air blown to the nonwoven fabric 10. As a method for recovering the bulk of such a nonwoven fabric, for example, the techniques described in JP 2004-137655 A, JP 2007-177364 A, and JP 2008-231609 A related to the earlier application of the applicant of the present application are used. Can be used.

  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, the concave portions of the nonwoven fabric 10 in the above embodiment have a rhombic lattice shape, but instead of this, dot-shaped concave portions that are dispersedly arranged in the form of dots may be employed. Moreover, you may employ | adopt the shape which makes a square or rectangular lattice shape, or a tortoiseshell pattern.

  Moreover, in the said embodiment, although hot embossing was used for formation of a junction part (concave part 18), it can replace with this and a junction part can also be formed by ultrasonic embossing. Moreover, the nonwoven fabric 10 is not restricted to the thing of a multilayer structure, A single layer structure may be sufficient. Furthermore, another nonwoven fabric may be further laminated on the back surface 10b side of the nonwoven fabric 10.

  Moreover, although the nonwoven fabric 10 of the said embodiment was uneven | corrugated on one surface of the two surfaces and the other surface was flat, it replaced with this and each surface is uneven | corrugated. May be.

  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 and Comparative Examples 1 and 2]
The multilayer nonwoven fabric 10 shown in FIG. 1 was manufactured using the apparatus shown in FIG. The pattern roll 41 in the apparatus shown in FIG. 2 has rhombic lattice-shaped convex portions with a line width of 0.5 mm. The area ratio of the convex part in this embossing roll 14 was 14%. As the low-temperature heat-extensible raw fiber and the high-temperature heat-extensible raw fiber, those shown in Table 1 were used. In Example 1, 4 dtex staple fiber having a core made of polypropylene (melting point: 161 ° C.) and a sheath made of polyethylene (melting point: 126 ° C.) was used as the low-temperature heat-extensible raw material fiber. The thermal elongation rate of the low-temperature thermally extensible raw fiber at 136 ° C. was 7.9%. As a high-temperature heat-extensible raw fiber, a 4 dtex staple fiber having a core made of polyethylene terephthalate (melting point 250 ° C.) and a sheath made of polyethylene (melting point 126 ° C.) was used. The thermal elongation rate of the high-temperature heat-extensible raw fiber at 136 ° C. was 8.3%. Production was carried out under the conditions shown in Table 1 below to obtain a nonwoven fabric. In the obtained nonwoven fabric, the intersections of the heat-extensible fibers were fused. About the obtained nonwoven fabric, various evaluation was performed with the following method. The results are shown in Table 1.

[The thermal elongation rate of the fiber at the convex portion of the nonwoven fabric]
The thermal expansion rate of the fiber in the convex part of the nonwoven fabric was measured and calculated in the following order 1-5.
1. Collection of fibers from nonwoven fabric Five fibers are collected from the upper and lower portions of the convex portion of the nonwoven fabric. The length of the fiber to be collected is 1 mm or more and 5 mm or less.
2. Measurement of the total length of the fiber collected from the nonwoven fabric The sampled fiber is sandwiched between the preparations, and the total length of the sandwiched fiber is measured. For measurement, a microscope VHX-900 and a lens VH-Z20R manufactured by KEYENCE were used. The measurement was performed by observing the fiber at a magnification of 50 to 100 times and using a measurement tool incorporated in the apparatus for the observed image. The length obtained by this measurement is defined as “the total length of fibers collected from the nonwoven fabric”.
3. Heat treatment of fibers collected from non-woven fabric Fibers collected from non-woven fabric whose total length was measured are put into a sample container for DSC6200 (product name: robot container 52-023P, 15 μL, made of aluminum) manufactured by SII Nano Technology Co., Ltd. The container containing the fibers is placed in a sample place in a heating furnace of DSC6200 that is set at 145 ° C. in advance. After the temperature (display name in the measurement software: sample temperature) measured with a thermocouple installed directly under the sample storage area of the DSC 6200 falls within the range of 145 ° C. ± 1 ° C., it is heated for 60 seconds and then quickly removed.
4). Measurement of the total length of the fiber after the heat treatment The fiber after the heat treatment is taken out from the DSC sample container and sandwiched between the preparations, and the total length of the sandwiched fiber is measured. For measurement, a microscope VHX-900 and a lens VH-Z20R manufactured by KEYENCE were used. The measurement was performed by observing the fiber at a magnification of 50 to 100 times and using a measurement tool incorporated in the apparatus for the observed image. The length obtained by this measurement is defined as “the total length of the fiber after the heat treatment”.
5. Calculation of thermal elongation rate (%) The thermal elongation rate (%) is calculated from the following equation.
Thermal elongation rate (%) = {(full length of fiber after heat treatment−full length of fiber collected from nonwoven fabric) ÷ (full length of fiber collected from nonwoven fabric)} × 100 [%]

[Thickness of nonwoven fabric]
A circular plate is placed on the measurement table, and the position of the upper surface of the plate in this state is set as a measurement reference point A. Next, the plate is removed, the non-woven fabric to be measured is placed on the measurement table, and the plate is placed thereon. The position of the upper surface of the plate in this state is B. The thickness of the nonwoven fabric to be measured is determined from the difference between A and B. The size and weight of the plate can be variously changed depending on the purpose of measurement, but here, measurement was performed using a circular plate having a weight of 12.5 g and a diameter of 56.4 mm so that the pressure exerted on the nonwoven fabric by the plate was 49 Pa. . A laser displacement meter (manufactured by Keyence Corporation, CCD laser displacement sensor KL-080) was used as a measuring instrument. Instead of this, a dial gauge thickness gauge may be used.

[Fuzz preventing property on the surface 10a of the nonwoven fabric]
The surface 10a of the nonwoven fabric 10 was evaluated by the following method in the state after bulk recovery by hot air, and was set as fuzz preventing property. The processing temperature for bulk recovery was 110 ° C., the wind speed was 2.5 m / sec, and the processing time was 3 sec.
The nonwoven fabric is folded in two along the MD direction so that the convex portions are on the outside. At this time, the center of the convex portion is made to be the apex of the bent nonwoven fabric. The state in which the nonwoven fabric was visually observed from the horizontal direction with the vertex facing upward was determined according to the following criteria.
○: There is no fuzz clearly. ○ △: Slight but not clear. Δ: Fluffing X: There is much fuzzing.

[Bulk recoverability of nonwoven fabric]
The bulk recovery property was evaluated by the following procedure.
1. Sample preparation A weight or the like was applied to the nonwoven fabric 10 so as to have a pressure of 4.9 kPa, and the sample was allowed to stand in a 50 ° C. environment for 10 days (240 hours) to evaluate bulk recovery. There is no particular restriction on the sample size. The sample left standing for 10 days is referred to as non-woven fabric 10 after storage.
2. Initial thickness measurement The thickness of the nonwoven fabric 10 before storage is measured by the method described in the above section [Nonwoven fabric thickness]. This thickness is called the initial thickness.
3. Bulk recovery treatment The thickness of the nonwoven fabric was recovered by blowing hot air onto the nonwoven fabric 10 after storage. The said process is called a bulk recovery process, and the nonwoven fabric 10 after the storage which performed the bulk recovery process is called the nonwoven fabric 10 after a bulk recovery process. Here, the processing temperature for bulk recovery is 110 ° C., the wind speed is 2.5 m / sec, and the processing time is 3 sec.
4). Thickness measurement after bulk recovery treatment The thickness of the nonwoven fabric 10 after the bulk recovery treatment is measured by the method described in the above section [Thickness of the nonwoven fabric]. This thickness is called the thickness after bulk recovery.
5. Calculation of bulk recoverability (%) Bulk recoverability is calculated by the following formula.
Bulk recovery (%) = (Thickness after bulk recovery ÷ initial thickness) × 100
In addition, let bulk recovery property (%) be the average value with respect to five nonwoven fabrics.
The case where the bulk recovery property is less than 65% is evaluated as x, the case where it is 65 or more and less than 75% is evaluated as Δ, and the case where it is 75% or more is evaluated as ○. The higher the bulk recovery value, the higher the evaluation.

  As is apparent from the results shown in Table 1, it can be seen that the non-woven fabric obtained in each Example (product of the present invention) has less fuzz and is excellent in bulk recovery.

DESCRIPTION OF SYMBOLS 10 Nonwoven fabric 18 Concave part 19 Convex part 20 Manufacturing apparatus 30 Web manufacturing part 40 Embossing part 50 Hot air blowing part

Claims (8)

A non-woven fabric including a heat-extensible fiber whose length is extended by heating and having a large number of convex portions and concave portions on one surface side, and the heat-extensible fiber constituting the convex portion has a thermal elongation rate of The lower part is higher than the upper part of the convex part,
As the raw fiber of the heat-extensible fiber, two or more types of heat-extensible raw material fibers having different temperatures at which thermal extension is started are used.
The upper side of the convex part is formed using a low-temperature heat-extensible raw fiber that starts thermal elongation at a relatively low temperature, and the lower part of the convex part is a high-temperature heat-extensible raw fiber that starts thermal extension at a relatively high temperature. Nonwoven fabric that is formed using   The thermally extensible fiber includes a first resin component made of a high melting point resin and a second resin component made of a low melting point resin having a melting point lower than the melting point of the first resin component, and the second resin component is a fiber surface. The nonwoven fabric according to claim 1, wherein the nonwoven fabric is a composite fiber in which at least a part of the fiber is continuously present in the length direction.   At the melting point + 20 ° C. of the low-melting resin constituting the heat-extensible fiber located above the convex portion, the thermal elongation rate of the heat-extensible fiber located above the convex portion is 0.1% or more and less than 3.0% The non-woven fabric according to claim 1 or 2, wherein the heat-extensible rate of the heat-extensible fibers located at the lower part of the convex portion is 3.0% or more and less than 20%.   The nonwoven fabric according to any one of claims 1 to 3, wherein the upper side of the convex portion includes a core-sheath type thermally stretchable conjugate fiber in which the first resin component is polypropylene and the second resin component is polyethylene.   The nonwoven fabric according to any one of claims 1 to 3, wherein a lower side of the convex portion includes a core-sheath type heat-extensible conjugate fiber in which the first resin component is polyethylene terephthalate and the second resin component is polyethylene.   The upper side of the convex portion includes a core-sheath type heat-extensible conjugate fiber in which the first resin component is polypropylene and the second resin component is polyethylene, the lower side of the convex portion is the first resin component is polyethylene terephthalate, The nonwoven fabric according to any one of claims 1 to 3, comprising a core-sheath type heat-extensible conjugate fiber in which the two resin components are polyethylene.   An absorbent article comprising a nonwoven fabric according to claim 1, wherein the nonwoven fabric is arranged such that a surface of the nonwoven fabric having convex portions and concave portions faces a wearer's skin. Heat is applied to a web having a layer containing a low-temperature heat-extensible raw material fiber that starts thermal elongation at a relatively low temperature on a layer containing a high-temperature heat-extensible raw material fiber that starts heat extension at a relatively high temperature. Consolidate with or without it to form multiple joints,
Next, hot air is blown from the side of the layer containing the low-temperature heat-extensible raw fiber that starts thermal expansion at a relatively low temperature, and both the heat-extensible raw fibers between the joints are heat-extended to form a large number of convex portions and concave portions. A method for producing a nonwoven fabric, comprising:
A method for producing a nonwoven fabric, in which the blowing of hot air is terminated before the two heat-extensible raw fibers are completely heated.

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