JP2011252252A - Nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonwoven fabric which has a hardly fluffed surface side and an excellent bulkiness recovery when subjected to post processing for a bulkiness recovery such as a hot air blowing.SOLUTION: A nonwoven fabric 10 having thermally expansile fibers which elongate by heat includes a plurality of convex parts 19 and concave parts 18 on one side thereof. In the thermally expansile fibers constituting the convex parts 19, their thermal elongation rates of upper parts 19a of convex parts 19 are higher than those of lower parts 19b thereof. At a temperature that is 20 degrees higher than the melting point of a resin constituting the thermally expansile fibers in the upper parts 19a of the convex parts 19, the thermal elongation rates of the fibers in the upper parts 19a of convex parts 19 are preferably 0.5% or more and less than 50%, and the thermal elongation rates of the fibers in lower parts 19b of convex parts 19 are preferably -50% or more and less than 0.5%.

Description

  The present invention relates to a nonwoven fabric containing heat-extensible fibers that are elongated 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 investigations by the present inventors on the nonwoven fabric made from heat-extensible fibers, the fiber elasticity of the heat-extensible fibers is lower than that of ordinary heat-fusible fibers, which It was found that when a load is applied in the thickness direction, the bulk is reduced and the interfiber distance tends to be shortened. When such a nonwoven fabric is used as, for example, a surface sheet of an absorbent article, the excreted liquid may easily remain in the nonwoven fabric due to a short interfiber distance.

JP 2005-350836 A

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

  The present invention includes a heat-extensible fiber whose length is increased by heating, and has a plurality of convex portions and concave portions on one surface side, and the fiber constituting the convex portion has a thermal elongation rate. The present invention provides a nonwoven fabric in which the upper part is higher than the lower part of the convex part.

  In the nonwoven fabric of the present invention, since the fibers located on the surface side are easily stretched, when the nonwoven fabric is subjected to post-processing for bulk recovery such as blowing hot air, the fibers on the surface side are thermally stretched, Bulk recovery is improved. Moreover, since the fiber-to-fiber distance on the front surface side is increased by the bulk recovery and the capillary force is relatively lowered as compared with the back surface side, a capillary force gradient from the front surface side to the back surface side is generated. As a result, the permeability of the liquid becomes high, and it is difficult for the liquid that has permeated to reverse.

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. 1A) is substantially flat, and the other side (the front surface 10a in FIG. 1A) 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 constituent fibers of the nonwoven fabric 10 are fused at their intersections. Since the intersections of the fibers are heat-sealed in 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. Examples of the heat-extensible fibers include fibers that are changed by changing the crystalline state of the resin by heating, or fibers that have been crimped and have an apparent length that is released by crimping. It is done. 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 (hereinafter 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. Moreover, the nonwoven fabric 10 may contain the non-heat extensible fiber. Particularly preferably used non-heat-extensible fibers include a first resin component made of a high-melting 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 is substituted. And a second resin component made of a low melting point resin, 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. The second resin component in the composite fiber is a component that exhibits heat-fusibility. Details of the heat-extensible fibers and non-heat-extensible fibers will be described later.

  In each convex part 19 of the nonwoven fabric 10, there is a difference in the thermal elongation rate between the fiber located in the upper part 19a of the convex part 19 and the fiber located in the lower part 19b. The present invention has one of the features in this respect. Specifically, when compared at the same heating temperature, the fiber constituting the convex portion 19 is relatively higher in thermal expansion rate in the one located in the upper portion 19a than in the lower portion 19b of the convex portion 19. It is high. That is, when heat at a certain temperature is applied, the fiber located at the upper part 19a of the convex part 10 has a larger degree of elongation than the fiber located at the lower part 19b. In other words, the fiber located in the lower part 19b of the convex part 10 is less stretched than the fiber located in the upper part 19a. Since the degree of thermal expansion of the fibers contained in the protrusions 19 is such, the fibers located on the surface 10a side of the nonwoven fabric 10 are likely to be thermally expanded, so that the nonwoven fabric is recovered in bulk, such as by blowing hot air. Therefore, when subjected to post-processing, the fiber on the surface 10a side is thermally stretched, and an advantageous effect is obtained that the bulk recovery property is improved. Further, the bulk recovery makes the interfiber distance on the front surface 10a side larger than the interfiber distance on the back surface 10b side, and the capillary force is relatively lowered on the front surface 10a side than on the back surface 10b side. This causes a capillary force gradient from the front surface 10a side to the back surface 10b side. As a result, the permeability of the liquid is increased, and there is an advantageous effect that it is difficult for the liquid that has permeated to reverse.

  The thermal elongation rate of the fibers contained in the convex portion 19 may gradually increase from the lower portion 19b toward the upper portion 19a, or may increase 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, a heat-extensible fiber is used as at least one kind of fiber located on the upper part of the convex portion, and the melting point of the low-melting resin constituting the heat-extensible fiber is + 20 ° C. (In the case of a resin having no melting point, at a temperature of the softening point + 20 ° C.), the thermal stretch rate of the heat stretchable fiber located on the upper portion 19a of the convex portion 19 is 0.5% or more and less than 50%, particularly 0.5 % Or more and less than 20%, particularly preferably 0.9% or more and less than 10%. On the other hand, the thermal elongation rate of the fiber located in the lower portion 19b of the convex portion 19 is −50% or more and less than 0.5%, particularly −20% or more and less than 0.5%, especially −10% at the above temperature. As mentioned above, it is preferable that it is less than 0.4%. This thermal elongation rate is measured for the fibers contained in the convex portion 19. A method for measuring the thermal elongation rate will be described later. A negative value for the thermal elongation means that the fiber shrinks due to heat.

  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 can be 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. Moreover, as a fiber used as the raw material of the nonwoven fabric 10, in addition to the heat-extensible raw material fiber, a non-heat-extensible fiber can be used. In the following description, the non-heat-extensible fiber contained in the nonwoven fabric 10; For the purpose of distinguishing the non-heat-extensible fibers that are the raw material of the nonwoven fabric 10, the non-heat-extensible fibers that are the raw material of the nonwoven fabric 10 are referred to as “non-heat-extensible raw fibers”. When it is simply referred to as “non-heat-extensible fiber”, it refers to a non-heat-extensible fiber contained in the nonwoven fabric 10.

  It is preferable to use a combination of a heat-extensible raw material fiber and a non-heat-extensible raw material fiber as a raw material for the nonwoven fabric 10. In this case, it is preferable that the upper part 19a side of the convex part 19 is formed using a heat-extensible raw material fiber, and the lower part 19b side of the convex part 19 is formed using a non-heat-extensible raw material fiber. The blending ratio (weight) of both is expressed as a ratio of heat-extensible raw fiber: non-heat-extensible raw fiber, preferably 95: 5 to 5:95, more preferably 80:20 to 20:80, and still more preferably. Is from 60:40 to 40:60, more preferably from 55:45 to 45:55. A preferred method for producing the nonwoven fabric 10 will be described later.

  As the fiber used as the raw material of the nonwoven fabric 10, two types of heat-extensible raw material fibers having different temperatures at which thermal expansion starts can be used. In other words. A heat-extensible raw fiber that stretches at a relatively high temperature (hereinafter referred to as “high-temperature stretchable raw fiber”) and a heat-extensible raw fiber that stretches at a relatively low temperature (hereinafter “low-temperature stretchable raw fiber”) Say). 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 high-temperature-extensible raw material fibers, and the lower portion 19b side of the convex portion 19 is formed using low-temperature extensible raw material fibers. It is preferable to be formed. The blending ratio (weight) of both is expressed as a ratio of high-temperature-extensible raw fiber: low-temperature-extensible raw fiber, preferably 95: 5 to 5:95, more preferably 80:20 to 20:80, and still more preferably. 60:40 to 40:60, still more preferably 55:45 to 45:55.

  The heat-extensible raw fiber (including the low-temperature extensible raw fiber and the high-temperature 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 component component made of a low melting point resin having a softening point, wherein the second resin component is present continuously in the length direction at least part of the fiber surface (hereinafter referred to as this component). The fiber 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-extensible composite raw fiber has a thermal elongation rate of 0.5 to 20%, particularly 3 to 20%, especially 5 to 20% at a temperature 10 ° C higher than the melting point or softening point of the second resin component. Is preferred. The nonwoven fabric 10 manufactured using such a fiber having a thermal elongation rate as a raw material becomes bulky due to the elongation of the fiber in the manufacturing process of the nonwoven fabric 10 or has a three-dimensional appearance. 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 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.

  When two types of heat-extensible raw fiber are used, the upper portion 19a side of the convex portion 19 of the nonwoven fabric 10 includes a core-sheath type heat-extensible composite fiber in which the core is polyethylene terephthalate and the sheath is polyethylene, and the convex portion 19 includes a core-sheath type heat-stretchable composite fiber in which the core is polypropylene and the sheath is polyethylene, so that the bulk recovery of the nonwoven fabric 10 when hot air is blown onto the nonwoven fabric 10 can be made more remarkable. To preferred.

  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.

  When using a heat-extensible raw material fiber and a non-heat-extensible raw material fiber in combination, the non-heat-extensible raw material fiber is composed of two components having different melting points and is subjected to a drawing treatment. It is preferable to use a fusible conjugate fiber. The heat-fusible conjugate fiber does not substantially extend its length even when heat is applied. In some cases, it may shrink slightly. The non-thermally stretchable raw fiber has a thermal stretch rate at a temperature 20 ° C. higher than the melting point or softening point of the second resin component of −50% to 0.5%, particularly −20 to 0.4%, especially −10. % To 0.1% is preferable. This heat-fusible conjugate fiber is a bicomponent conjugate fiber that includes a high-melting-point component and a low-melting-point component, and the low-melting-point component is continuously present in the length direction on at least a part of the fiber surface. . There are various forms of the composite fiber such as a core-sheath type and a side-by-side type, and any form can be used. The heat-fusible conjugate fiber is stretched at the raw material stage (that is, before being used for the nonwoven fabric 10). The stretching treatment referred to here is a stretching operation with a stretching ratio of about 2 to 6 times.

  The fiber lengths of the heat-extensible raw material fiber and the non-heat-extensible raw material fiber are of appropriate lengths depending on 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. On the other hand, the fiber diameter of the non-heat-extensible fibers contained in the nonwoven fabric 10 is 10 to 35 μm, particularly 15 to 30 μm, particularly 15 to 15 μm when the nonwoven fabric 10 is used as a constituent member of an absorbent article such as a surface sheet of the absorbent article. It is preferable that it is 25 micrometers.

  In addition to the fibers described above, the nonwoven fabric 10 may additionally include, for example, fibers that do not inherently have heat-fusibility (for example, natural fibers such as cotton and pulp, rayon, and acetate fibers).

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 used for the same application, the thickness of the nonwoven fabric 10 is preferably 0.5 to 3 mm, particularly 0.7 to 3 mm after bulk recovery by hot air (this will be described later). 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 part 30, the web 10a is manufactured using the heat | fever extensible raw material fiber and the non-heat extensible raw material fiber as needed. As the heat-extensible raw fiber, it is preferable to use a two-component composite fiber including the first resin component and the second resin component described above.

  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 heat-extensible raw fiber. The card machine 31b is supplied with non-heat-extensible raw fiber. When two types of heat-extensible fibers are used, the card machine 31a is supplied with high-temperature-extensible raw fiber, and the card machine 31b is supplied with low-temperature-extensible raw fiber.

  The webs formed by the respective card machines are laminated to form a web 10a. In the web 10a, the heat-extensible raw fiber is located in the upper layer, and the non-heat-extensible raw fiber is located in the lower layer. When two types of heat-extensible fibers are used, the high-temperature-extensible raw fiber is located in the upper layer, and the low-temperature-extensible raw fiber is located in the lower layer. The fibers located in the upper layer of the web 10a mainly constitute the upper side 19a of the convex portion 19 of the manufactured nonwoven fabric 10. The fibers located in the lower layer of the web 10a mainly constitute the lower side 19b of the convex portion 19. In the following description, the surface of the web 10a where the heat-extensible raw fiber (or high-temperature extensible raw fiber) is present is referred to as the first surface 101, and the non-heat-extensible raw fiber (or low-temperature extensible raw material) is used. The surface on the side where the (fiber) exists is called a second surface 102. 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 in a state where its constituent fibers are loosely entangled with each other, and the shape retention as a sheet is not achieved. Therefore, in order to impart shape retention as a sheet to the web 10a, the web 10a is processed in the embossing section 40 to form the embossed web 10b.

  The embossing part 40 is provided with a pair of rolls 41 and 42 arranged to face each other with the web 10a interposed therebetween. Both rolls are separated by a predetermined clearance. 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 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 to produce the embossed web 10b. 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.

  In the embossing section 40, when heating at least one of the pattern roll 41 and the flat roll 42, the heating temperature is preferably set as follows. That is, when the combination of the heat-extensible raw fiber and the non-heat-extensible raw fiber is adopted, the melting point of the second resin component in the heat-extensible raw fiber is −20 ° C. or higher and lower than the melting point of the first resin component. It is preferable. When the combination of the high-temperature-extensible raw fiber and the low-temperature-extensible raw fiber is employed, the melting point of the second resin component in the low-temperature-extensible raw fiber is preferably −20 ° C. or higher and lower than the melting point of the first resin component. .

  The embossed web 10 b to which shape retention is imparted by the processing 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 (the high-temperature extensible raw fiber and the low-temperature extensible raw fiber) in the embossed web 10b is elongated by heating. In addition, the intersection of the heat-extensible raw fibers (high-temperature-extensible raw fibers and low-temperature-extensible raw fibers) in a free state existing in a portion other than the embossed portion of the embossed web 10b and the non-heat-extensible raw fibers are heat-sealed. Done at the temperature you want.

  The temperature of the hot air is preferably set as follows. That is, when a combination of a heat-extensible raw fiber and a non-heat-extensible raw fiber is adopted, the temperature is set so that the heat-extensible raw fiber is thermally extended. Further, the temperature is set such that the heat-extensible raw fiber is fused and the non-heat-extensible raw fiber is fused. Specifically, the temperature of the hot air is preferably not lower than the melting point of the second resin component of the 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 heat-extensible raw fiber is elongated. On the other hand, the non-heat stretchable fiber does not substantially stretch and maintains the original length substantially. Since a part of the heat-extensible raw fiber is fixed by the embossed portion, the stretched portion is a portion between the embossed portions. Further, since a part of the heat-extensible raw fiber is fixed by the embossed portion, the stretch of the stretched fiber loses its place in the plane direction of the embossed web 10b, and in the thickness direction of the embossed web 10b. Moving. 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. Further, the intersections of the heat-extensible raw material fibers are fused, and the intersection points of the non-heat-extensible raw material fibers are fused.

  On the other hand, when the combination of the high-temperature-extensible raw material fiber and the low-temperature-extensible raw material fiber is adopted, the temperature of the hot air is set to a temperature at which both the high-temperature-extensible raw material fiber and the low-temperature-extensible raw material fiber are thermally extended. Moreover, it is set as the temperature which high temperature extensibility raw material fibers fuse | melt and low temperature extensibility raw material fibers fuse | melt. Specifically, the temperature of the hot air is preferably not lower than the melting point of the second resin component of the low-temperature-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 stretchable raw fiber and the high-temperature stretchable raw fiber are stretched. And the convex part 19 is formed between embossed parts resulting from the expansion | extension, 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 intersections of the high-temperature-extensible raw fibers are fused, and the intersections of the low-temperature-extensible raw fibers are fused.

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

  When a combination of heat-extensible raw fiber and non-heat-extensible raw fiber is used, the blowing of hot air is completed before the heat-extensible raw fiber is fully extended. In addition, the heat-extensible raw fiber can be further extended. On the other hand, the non-heat-stretchable raw fiber does not substantially stretch even when heat treatment is further performed. For this reason, in the obtained nonwoven fabric 10, the fiber constituting the convex portion 19 has a higher thermal elongation rate measured at the same temperature in the upper portion 19 a than in the lower portion 19 b of the convex portion 19.

  When a combination of high-temperature-stretchable raw fiber and low-temperature-stretchable raw fiber is used, the degree of elongation of the low-temperature-stretchable raw fiber is higher than that of the high-temperature-stretchable raw fiber due to the lower temperature at which stretching starts. Becomes larger. As a result, when the heat treatment is further performed, the low-temperature-extensible raw fiber has a lower thermal elongation rate, so that the thermal elongation rate is relatively low. In other words, when the heat treatment is further performed, the high-temperature-extensible raw fiber has a relatively high thermal elongation rate because it has a larger thermal elongation elongation. For this reason, in the obtained nonwoven fabric 10, the fiber constituting the convex portion 19 has a higher thermal elongation rate measured at the same temperature in the upper portion 19 a than in the lower portion 19 b of the convex portion 19.

  The nonwoven fabric 10 obtained in this way can be applied to various fields that take advantage of the uneven shape and bulkiness. 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 first resin component in the heat-extensible fiber and a temperature equal to or higher than the melting point −50 ° C. as the hot air blown to the nonwoven fabric 10. When two types of heat-extensible raw material fibers are used, it is preferable to use hot air having a temperature lower than the melting point of the first resin component in the low-temperature extensible raw material fibers and a temperature of the melting point −50 ° C. or higher. 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]
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 heat-extensible raw fiber, a 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. The heat extension rate of the heat-extensible raw fiber at 136 ° C. was 7.9%. Moreover, the fiber elastic modulus measured by the following fiber elastic modulus measuring method was 0.6 MPa. As the non-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 heat elongation rate of the non-heat-extensible raw fiber at 136 ° C. was −1.3%, and the fiber elastic modulus was 1.3 MPa. 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. Also, the intersection of non-heat extensible fibers was fused. About the obtained nonwoven fabric, various evaluation was performed with the following method. The results are shown in Table 1.

[Fiber 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 to the curve when the strain is 0.1% is defined as the fiber elastic modulus.

[Comparative Examples 1 and 2]
A nonwoven fabric was obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were employed. 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.

[Liquid remaining amount in non-woven fabric]
The surface sheet is removed from a commercially available sanitary napkin (trade name “with Laurie Sarasara cushion wing” manufactured by Kao) to obtain a napkin absorbent body. Moreover, the nonwoven fabric to be measured is cut into MD120 mm × CD60 mm to produce a cut piece. The cut piece is placed at a position where the top sheet of the napkin absorbent body was present (on the skin contact surface of the napkin absorbent body), and the back surface 10a of the nonwoven fabric 10 in FIG. A sanitary napkin using the nonwoven fabric to be measured as a surface sheet is obtained so as to be on the opposite surface. An acrylic plate having a cylindrical transmission hole is placed on the surface of a sanitary napkin that uses the nonwoven fabric to be measured, and a constant load of 100 Pa is applied to the napkin. Under such a load, 3.0 g of defibrinated horse blood is poured from the permeation hole of the acrylic plate. 120 g after pouring defibrinated horse blood, another 3.0 g of defibrinated horse blood is poured. A total of 6.0 g of defibrinated horse blood was poured, and 60 seconds later, the acrylic plate was removed, and then the weight (W2) of the nonwoven fabric was measured. And the difference (W2-W1) with the weight (W1) of the nonwoven fabric before pouring defibrillated horse blood measured beforehand is calculated. The above operation is performed three times, and the average value of the three times is defined as the remaining liquid amount (mg). The liquid remaining amount is an index of how much the wearer's skin gets wet. The smaller the liquid remaining amount, the higher the evaluation.

[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 nonwoven fabric obtained in the examples (the product of the present invention) has a small amount of liquid remaining and high liquid permeability. It can also be seen that it is excellent in bulk recovery when heat-treated.

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 (5)

  A non-woven fabric that includes a heat-extensible fiber that elongates by heating and has a large number of convex portions and concave portions on one surface side, and the fiber constituting the convex portion has a thermal elongation rate lower than that of the lower portion of the convex portions. Nonwoven fabric with higher upper part. On the upper part of the convex part, as a heat-extensible fiber, a heat-extensible composite fiber containing a high-melting point resin and a low-melting point resin having a lower melting point is located,
At the melting point of the low-melting point resin + 20 ° C., the thermal stretch rate of the thermally stretchable conjugate fiber located at the top of the convex portion is 0.5% or more and less than 50%,
The nonwoven fabric according to claim 1, wherein the fiber located at the lower part of the convex portion has a thermal elongation of −50% or more and less than 0.5%.   The nonwoven fabric according to claim 1 or 2, wherein an upper side of the convex portion is formed using a heat-extensible raw material fiber, and a lower side of the convex portion is formed using a non-heat-extensible raw material fiber.   The upper part of the convex part is formed using a heat-extensible raw material fiber that thermally expands at a relatively high temperature, and the lower part of the convex part is formed using a heat-extensible raw material fiber that heat-extends at a relatively low temperature. The nonwoven fabric according to claim 1 or 2.   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.