TW201326486A - Fibers with thermal elongation properties and non-woven fabric using same - Google Patents

Abstract

These fibers with thermal elongation properties comprise a first resin component, and a second resin component having a melting point or a softening point that is lower than the melting point of the first resin component, and at least part of the fiber surface of the second resin component is continuously present in the length direction, and the length extends as a result of applying heat. The rate of change ({(B - A)/A} 100) of the thermal elongation B at the melting point of the second resin component plus 10 DEG C with respect to the thermal elongation A at the melting point of the second resin component minus 6 DEG C is at least 130%. The first resin component preferably comprises polylactic acid, while the second resin component preferably comprises a polyolefin. The ratio (crimp rate (%)/number of crimps (count)) between the crimp rate (%) measured in accordance with JIS L1015 and the number of crimps (count) measured in accordance with JIS L1015 is preferably between 0.45 and 0.75.

Description

Heat-extensible fiber and non-woven fabric using the same

This invention relates to a thermally elongated fiber. Further, the present invention relates to a nonwoven fabric produced using the heat-extended fiber.

Various heat-expandable fibers containing a composite fiber including a first component and a second component having a lower melting point than the first component are known. In the combination of the first component and the second component, polypropylene/polyethylene or polyethylene terephthalate/polyethylene or the like is present. Specifically, the applicant has previously proposed a heat-extensible fiber containing a core-sheath type composite fiber having a polypropylene core and a sheath of polyethylene, and an alignment index of polypropylene and polyethylene. (Orientation index) is set in a specific range (refer to Patent Document 1).

For the heat-expandable fiber containing polyethylene terephthalate/polyethylene, for example, Patent Document 2 is known. The heat-extensible fiber is obtained by using an unstretched yarn of a composite fiber extracted at a spinning speed of 150 m/min or more and 1800 m/min or less at a glass transition point higher than polyethylene and polyethylene terephthalate. At a temperature of both of the glass transition points, a fixed length heat treatment is performed at 0.5 to 1.3 times, and thereafter, heat treatment is performed in a relaxed state at a temperature higher than the fixed length heat treatment temperature by 5 ° C or higher.

The conjugate fiber containing the first component and the second component having a low melting point as the first component as the non-heat-extensible fiber is also known to contain polylactic acid/polyethylene in addition to the combination of the above resins. For example, Patent Document 3 proposes a thermally-adhesive composite fiber containing a first component containing polylactic acid and a second component containing polyethylene having a melting point lower than a melting point of polylactic acid by 20 degrees or more. dimension. In the thermal adhesive composite fiber, by adding inorganic fine particles to the resin of the first component and/or the second component, the stretching ratio is 75% or more and 90% or less of the elongation at break of the unstretched fiber, and heating is performed. The temperature is a range in which the glass transition point (Tg) of the first component is +10° C. or higher to the melting point of the second component of −10° C. or less, and then the melting point is lower than the melting point of the second component but 15° C. It is produced by heat treatment at a temperature not lower.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-218183

Patent Document 2: Japanese Patent Laid-Open Publication No. 2007-204901

Patent Document 3: Japanese Patent Laid-Open Publication No. 2008-274448

The heat-expandable fiber which has been known to the present invention includes the heat-expandable fiber described in Patent Documents 1 and 2, and generally has a gradually longer length as the temperature of the heating increases. When such a heat-extensible fiber is used as a raw material, when a nonwoven fabric is produced by, for example, a thermal bond method, a certain degree of elongation occurs in the fiber due to heat of heat bonding, and therefore, after the nonwoven fabric is manufactured, As the post-processing, it is difficult to heat the fiber in the fluffy recovery treatment step, for example, so that the fiber is further elongated, and the degree of elongation at the time of imparting a bulkiness is increased. In addition, since the heat-bondable composite fiber described in the above Patent Document 3 does not have thermal elongation, it is difficult to impart fluffiness when a non-woven fabric is produced by using, for example, a heat-bonding composite fiber as a raw material. sense.

The present invention provides a heat-expandable fiber comprising a first resin component and a second resin component having a melting point or a softening point lower than a melting point of the first resin component, and the second resin component continuously exists in the longitudinal direction. At least a part of the surface of the fiber, and the length of the fiber is elongated by heating, and the melting point of the second resin component + the rate of change of the thermal elongation B at 10 ° C with respect to the melting point of the second resin component at a temperature of -6 ° C ( {(BA)/A}×100) is 130% or more.

Moreover, the present invention provides a nonwoven fabric which uses the above-mentioned heat-extensible fiber as a raw material, and has a plurality of convex portions and concave portions on one surface side, and the other surface side is flatter than one surface side, and contains heat elongation in the convex portion. In the state of the heat-extensible fiber, the thermal elongation C of the thermally extensible fiber in the thermally stretched state at the position corresponding to the convex portion on the surface of the other surface side corresponds to the convex portion in the surface existing on one surface side. The ratio (C/D) of the thermal elongation D of the thermally extensible fiber in the thermally stretched state at the position is 3 or more at the melting point + 20 ° C of the second resin component constituting the thermally extensible fiber.

Further, the present invention provides a nonwoven fabric using the above-mentioned heat-expandable fiber as a raw material, and the nonwoven fabric has a plurality of convex portions and concave portions on one surface side, and a plurality of convex portions and concave portions on the other surface side, and one side surface The convex portion and the concave portion and the convex portion and the concave portion on the other surface side are located at the same position in the plan view of the nonwoven fabric, and the heat-extensible fiber in the heat-extended state in the convex portion exists at a position corresponding to the convex portion on the surface on the other surface side. Thermal elongation The thermal elongation E of the thermal extensible fiber and the ratio (E/F) of the thermal elongation F of the thermally extensible fiber in the thermally stretched state at the position corresponding to the convex portion on the surface on one side are constituting heat The melting point of the second resin component of the extensible fiber is 0.1 or more and less than 3 in 20 ° C, and the thickness of the convex portion on the other surface side in the thickness direction of the non-woven fabric in the convex portion occupies the entire convex portion. The thickness is 20% or more and 40% or less.

Furthermore, the present invention provides a method for producing a thermally extensible fiber, wherein the spinning temperature of the first component is set to a melting point of the first component plus a range of from 20 ° C to 180 ° C, and the spinning temperature of the second resin component is set. The melting point of the second component is set to a range of 20° C. or more and 180° C. or less, and melt spinning is performed at a spinning speed of 50 m/min or more and 1500 m/min or less, and the crimping treatment is performed without stretching, and thereafter The relaxation treatment is performed by heating and drying at 100 ° C or more and 125 ° C or less.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments thereof. The heat-expandable fiber of the present invention is a composite fiber comprising a first resin component containing a high melting point resin and a low melting point resin containing a melting point or a softening point lower than a melting point of the first resin component. 2 A resin component, and the second resin component continuously exists in at least a part of the fiber surface in the longitudinal direction. The first resin component of the thermally extensible fiber exhibits a thermal extensibility component of the fiber, and the second resin component exhibits a hot melt. The ingredients of the nature. The heat-expandable fiber of the present invention can be elongated by heat at a temperature lower than the melting point of the first resin component. In general, the temperature range of the thermal elongation is in the range from -60 ° C of the melting point of the second resin component to the melting point of the first resin component.

The heat-expandable fiber of the present invention is typically a core-sheath type composite fiber containing a first resin component and a second resin component. Alternatively, it may be a Side by Side type composite fiber. In the case where the heat-extensible fiber of the present invention is a core-sheath type, the heat-extensible fiber may be concentric or may be eccentric.

The heat-expandable fiber of the present invention is characterized by a high rate of change in thermal elongation between two specific temperatures. Specifically, this is characterized in that the thermal elongation at the melting point of the second resin component at -6 ° C is A, and the thermal elongation at the melting point of the second resin component + 10 ° C is B, and the thermal elongation is The rate of change of B with respect to the thermal elongation A (hereinafter referred to as "thermal elongation change rate"), that is, {(BA) / A} × 100 is 130% or more, preferably 135% or more, and more preferably 150. Higher value above %. The upper limit of the value is not particularly limited, but specifically, it is preferably 300% or less, and particularly preferably 210% or less. The rate of change in thermal elongation is, for example, preferably 130% or more and 300% or less, and preferably 135% or more and 210% or less. The above features will be described with reference to FIG.

The table shown in Fig. 1 indicates the temperature (°C) on the horizontal axis and the elongation (mm) of the fiber on the vertical axis. In the figure, A represents the heat-expandable fiber of the present invention, and B represents the prior heat-extended fiber (the core component is a polypropylene/sheath component is polyethylene). According to the figure, the heat-extensible fiber A of the present invention is at a certain temperature. Before the degree T1, the temperature gradually increases as the temperature rises, and if the temperature T1 is exceeded, the degree of elongation rapidly increases. As a result, the table of the temperature-elongation amount includes the line L1 having the first slope S1 and the line L2 having the second slope S2. The temperature at the intersection of the line L1 and the line L2 is the above temperature T1. The slopes S1 and S2 have a relationship of S1 < S2. In contrast, the previous heat-extensible fiber B gradually elongated only as the temperature rose, and no temperature at which the sharp change occurred in the slope of the table was observed.

The heat-expandable fiber of the present invention having a large rate of change in thermal elongation has the advantages described below. Since the heat elongation at a specific temperature is kept low, after the heat-expandable fiber is used to produce, for example, a heat-bondable nonwoven fabric, if it is post-processed, for example, heating is further performed in the fluffy recovery treatment step of the nonwoven fabric, it is easy to make The elongation of the heat-extensible fiber is further increased when the nonwoven fabric is given a bulky feeling. As a result, a fluffy non-woven fabric can be easily obtained.

The heat-expandable fiber-based second resin component of the present invention has a thermal elongation A of preferably 3.5% or less, particularly preferably 3.2% or less, particularly preferably from 3.2% to 5%. Good is less than 3.0%. Further, the lower limit of the thermal elongation A is preferably zero, or the positive value closer to zero is better. The temperature of the second resin component, the melting point of -6 ° C, refers to the temperature at which the fibers are initially fused to each other when the heat-expandable fiber of the present invention is subjected to thermal processing such as thermal bonding. On the other hand, the value of the melting point of the second resin component + the thermal elongation B at 10 ° C is not particularly limited, and the larger the ratio, the better. In general, the value of the elongation B is preferably 5% or more, and more preferably 8% or more. The temperature of the second resin component, the melting point + 10 ° C, means that the heat-expandable fiber of the present invention is thermally bonded. A representative temperature at the time of thermal processing.

As described with reference to Fig. 1, the heat-expandable fiber of the present invention preferably has a temperature T1 in Fig. 1 as a melting point of the second resin component - 10 ° C ≦ T1 ≦ a melting point of the second resin component - 3 ° C . Further, the closer the slope S1 of the line L1 in FIG. 1 is to zero, the better the slope S2 of the line L2 in FIG. 1 is larger.

The thermal elongation of the heat-extensible fiber was measured by the following method. A thermomechanical analysis device TMA (Thermal Mechanical Analysis) / SS6000 manufactured by Seiko Instruments Co., Ltd. was used. As a sample, a plurality of fibers having a length of 10 mm or more collected in a total weight of 10 mm per 10 mm of the fiber length are prepared, and the plurality of fibers are arranged in parallel, and the distance between the chucks is 10 mm is installed in the unit. The measurement start temperature was set to 25 ° C, and the temperature was raised at a temperature increase rate of 5 ° C / min under a fixed load of 0.73 mN / dtex, and the elongation of the fiber at this time was measured. When the elongation at the temperature T (° C.) is E _T (mm), the thermal elongation (%) at the temperature T (° C.) is calculated from (E _T /10) × 100 [%].

In order to achieve a characteristic that the thermal elongation is low before the specific temperature and the thermal elongation rate is increased when the temperature exceeds the specific temperature, for example, a combination of the resin used as the first resin component and the second resin component may be appropriately selected. As a result of the study by the inventors of the present invention, it has been found that it is effective to use the difference between the crystallization rates as the first resin component and the second resin component. Specifically, it is preferred to use a second resin component as the crystallization rate higher than the crystallization rate of the first resin component. For polyethylene, which is commonly used as a thermoplastic resin having fiber-like properties, namely, polyethylene (polyethylene), polypropylene (PP), Polyethylene terephthalate (PET) and polylactic acid (PLA) are considered. The sequence of crystallization rate of these resins is PE>PP>PET>PLA. Therefore, the first resin component and the second resin component may be selected in consideration of the crystallization rate of the resin and the melting point of the resin. As a combination of resins which are preferable from the viewpoints, the first resin component is polylactic acid, and the second resin component is a combination of polyolefins such as polyethylene or polypropylene. The combination of the resin of the utmost is that the first resin component is polylactic acid, and the second resin component is polyolefin. The combination of the particularly preferable resin is that the first resin component is polylactic acid, and the second resin component is polyethylene. The crystallization rate of the resin component was measured by a differential scanning calorimeter (DSC). First, the sample is heated at a melting point or higher (300 ° C) in the atmosphere to be melted, and then immediately quenched until a specific crystallization temperature is reached. When the temperature (crystallization temperature) was maintained, the time (crystallization time) from the start point of cooling to the peak of the crystallization of the crystallization observed in the DSC curve was measured, and the obtained time was defined as the crystallization rate. The quenching is carried out, for example, at a cooling rate of 100 ° C / min.

The quality of the first resin component and the second resin component in the thermally extensible fiber of the present invention is preferably the first resin component: the second resin component = 20: 80 to 80, from the viewpoint of easily achieving the above characteristics. : 20, further preferably 30:70 to 70:30.

The polylactic acid which is preferably used as the thermoplastic resin of the first resin component preferably has a melt index of 2 g/10 min or more, particularly preferably 5 g/10 min or more, and preferably 50 g. Below /10 min, it is preferably 40 g/10 min or less. On the other hand, the polyethylene which is preferably used as the thermoplastic resin of the second resin component preferably has a melt index of 10 g/10 min or more, and preferably 40 g/10 min or less, particularly preferably 25 g. /10 min or less. As the polyethylene, high-density polyethylene, low-density polyethylene, or linear low-density polyethylene can be used, but in terms of high tensile strength when not woven, it is preferred to use a density of 0.941 g/cm ³ or more. High density polyethylene of 0.965 g/cm ³ or less. The melt index of the first resin component and the second resin component was measured under the conditions of 190 ° C and a load of 2.16 kg in accordance with the method described in JIS (Japanese Industrial Standards) K7210.

In order to achieve the above characteristics relating to thermal elongation, it is also effective to control the alignment index of the first resin component and the second resin component. The alignment index is an indicator of the degree of alignment of the polymer chain of the resin component. As a result of the investigation by the inventors of the present invention, it has been found that the above-described characteristics relating to thermal elongation can be easily achieved by setting the orientation index of the first resin component to preferably 50% or less, more preferably 40% or less. More preferably, the polylactic acid is used as the first resin component, and the orientation index of the first resin component containing the polylactic acid is set to be equal to or less than the above value. The lower limit of the alignment index of the first resin component is preferably 3%, more preferably 10% or more.

On the other hand, the alignment index of the second resin component is preferably 5% or more, and more preferably 8% or more. It is particularly preferable to use the polyethylene as the second resin component, and it is preferable to set the orientation index of the second resin component containing polyethylene to the above range.

When the birefringence value of each resin component in the heat-expandable fiber of the present invention is A and the intrinsic birefringence value of each resin component is B, the orientation index of the first resin component and the second resin component is It is represented by the following formula (1).

Orientation index (%) = A / B × 100 (1)

The intrinsic birefringence refers to the birefringence in the state in which the polymer chain of the resin is completely aligned, and the value thereof is described, for example, in the "Plastic material in forming process", the representative plastic material used in the first edition, the attached table, and the forming process (plastic) Edited by the Society of Forming Processing, published by Sigma, and issued on February 10, 1998).

The birefringence of each resin component in the heat-expandable fiber of the present invention is measured by the following method. That is, the polarizing plate was attached to an interference microscope, and the measurement was performed under polarized light in a direction parallel to the fiber axis and in the vertical direction. A standard refractive liquid manufactured by Cargille Corporation was used as the immersion liquid. The refractive index of the immersion liquid was measured by an Abbe refractometer. According to the interference fringe image of the thermally extensible fiber obtained by the interference microscope, the refractive index in the parallel and perpendicular directions with respect to the fiber axis is obtained by the calculation method described in the following literature, and the difference between the two is calculated. refraction.

"Fiber structure formation in high-speed spinning of core-sheath type composite fibers", p. 408 (Journal of Fiber Society, Vol.51, No. 9, 1995)

In order to set the orientation index of each of the resin components in the thermally extensible fiber of the present invention to the above value or to achieve the above properties relating to thermal elongation, it is also effective to appropriately set the spinning condition of the thermally extensible fiber. Preferably, the heat-expandable fiber of the present invention is preferably produced by a melt spinning method, and the conditions at this time are appropriately set.

In the case where the heat-expandable fiber of the present invention is produced by a melt spinning method, a spinning device including a two-system extrusion device for each resin component and a spinning head can be used. A plurality of nozzles are bored in the spinneret. Since each The nozzles eject the first resin component and the second resin component in a molten state extruded from the respective extrusion devices so as to form a core-sheath type or a side-by-side type fiber. The molten resin ejected from the nozzle is extracted at a specific speed. An example of such a device is described in Fig. 1 of Patent Document 1.

In the above melt-spinning method, by adjusting the spinning temperature of the first resin component and the second resin component, the melt viscosity of each resin component can be balanced, and the intended heat-expandable fiber can be easily obtained. The spinning temperature of the first resin component is changed depending on the resin to be used. However, it is preferred to increase the melting point of the resin to be used in a range of from 20 ° C to 180 ° C. More preferably, the melting point of the resin to be used is 30 ° C or more and 170 ° C or less. The range is further preferably a range in which the melting point of the resin to be used is 70 ° C or more and 170 ° C or less. The spinning temperature of the second resin component is changed depending on the resin to be used. However, it is preferred to add a melting point of the resin to be used in a range of from 20 ° C to 180 ° C. More preferably, the melting point of the resin to be used is 30 ° C or more and 170 ° C or less. The range is further preferably a range in which the melting point of the resin to be used is 100 ° C or more and 170 ° C or less. For example, when polylactic acid is used as the first resin component and polyethylene is used as the second resin component, the spinning temperature of the first resin component is preferably set to 230 ° C or more and 250 ° C or less, and preferably 2 The spinning temperature of the resin component is set to be 240 ° C or more and 280 ° C or less. In addition, the spinning temperature means the temperature of the resin when it is ejected from the spinning head. This temperature is the same as the melt kneading temperature of the resin component in the extrusion apparatus.

From the viewpoint of easily obtaining the target thermally extensible fiber, it is preferred to also control the spinning speed of the fiber in the melt spinning method. The results of the study by the inventors of the present invention have been known to make the spinning speed preferably 50 m/min or more. 1500 m/min or less, more preferably 100 m/min or more and 1400 m/min or less, and a heat-extensible fiber having characteristics to be satisfied is obtained.

Since the fiber obtained by the melt spinning method is in an unextended state, the stretching process is usually performed as post-processing, and then the crimping treatment and the relaxation treatment are performed. In contrast, the results of the findings of the present inventors have found that in the case of producing the thermally extensible fiber of the present invention, it is preferred not to carry out the stretching process. Therefore, the thermally extensible fiber of the present invention is preferably substantially unextended. The term "substantially unextended" means excluding the intentional extension processing even if the degree is low. Thus, in the manufacture of thermally extensible fibers, unintended and inevitable occurrence of a low degree of elongation is included in "substantially unextended".

The crimping treatment of the fiber obtained by the melt spinning method can also be carried out in the case of producing the heat-expandable fiber of the present invention. As the crimping process, mechanical crimping can be performed. There are two-dimensional and three-dimensional shapes in the mechanical crimping process, and any aspect of the crimping can be performed in the present invention.

Preferably, the fiber after the crimping treatment is subjected to a relaxation treatment. The relaxation treatment is generally carried out by heating and drying the fibers. In the production of the heat-expandable fiber of the present invention, the rate of change in the coefficient of thermal elongation can be improved by performing the relaxation treatment of the heat drying at a high temperature. In the production of the ordinary fiber, the temperature of the heat drying is set to be lower than the melting point of the second resin component by 25 or more and 60 ° C or less. However, in the present invention, the temperature is heated and dried at a higher temperature than the temperature. Specifically, it is preferable to set the temperature of the heat drying to a range of the melting point of the second resin component of -26 ° C to the melting point of the second resin component of -1 ° C, and further preferably set the temperature of the heat drying to be the second temperature. The melting point of the resin component is from -16 ° C to the melting point of the second resin component of -6 ° C. When the high-density polyethylene is used as the second resin component, it is preferably a relaxation treatment by heating and drying at 100 ° C or higher, particularly preferably 110 ° C or higher, and preferably at 125 ° C or lower, particularly preferably The relaxation treatment of heating and drying is carried out at 120 ° C or lower.

The fiber which has been subjected to the relaxation treatment is cut into a specific length to become a staple fiber, and is a raw material of various fiber products. This short fiber is in a state of being crimped by performing the above-described crimping treatment. In the heat-expandable fiber of the present invention, the degree of crimping is determined by the crimp ratio (% measured in accordance with JIS L1015) in terms of the passability of the carding machine in the manufacturing process of the nonwoven fabric. It is preferably 5% or more and 20% or less, and more preferably 7% or more and 15% or less. For the same reason, the number of crimps measured in accordance with JIS L1015 is preferably 5 or more and 25 or less, and more preferably 10 or more and 20 or less. Further, when the ratio of the crimp ratio (%) to the number of crimps (volume ratio (%) / number of crimps) is preferably 0.45 or more and 0.75 or less, more preferably 0.50 or more and 0.70 or less, Not only is the passability of the carding machine good, but the heat-extensible fiber is easily released during elongation, which is advantageous.

The heat-expandable fiber of the present invention obtained by the above method is a short fiber, but may be in the form of a continuous filament according to a production method. Further, the fiber diameter of the heat-expandable fiber of the present invention depends on the specific use thereof, but is generally preferably 10 μm or more and 100 μm or less, and more preferably 15 μm or more and 90 μm or less.

The heat-extensible fiber of the present invention can be preferably used as the original of various fiber products. material. In particular, it can be preferably used as a raw material fiber of a nonwoven fabric. Fig. 2 (a) and (b) show an example of a nonwoven fabric using the heat-expandable fiber of the present invention as a raw material. The non-woven fabric 10 shown in the figure has a single layer structure. In the nonwoven fabric 10, the first surface 10a has a concavo-convex shape having a plurality of convex portions 19 and concave portions 18, and the second surface 10b is flatter than the first surface 10a. That is, it is a stereoscopic shape. The recessed portion 18 includes a joint portion formed by pressure-bonding the constituent fibers of the nonwoven fabric 10 together. Examples of the method of forming the joint portion include embossing with or without heat, ultrasonic embossing, and the like. On the other hand, the convex portion 19 becomes a non-compacted joint portion. The thickness of the recess 18 is smaller than the thickness of the projection 19. The convex portion 19 is formed in a shape that is raised toward the first surface 10a side of the nonwoven fabric 10. The convex portion 19 is filled with the constituent fibers of the nonwoven fabric 10. In the convex portion 19, the thermally extensible fibers which are constituent fibers of the nonwoven fabric 10 are fused to each other at the intersections thereof. Due to the convex portion 19, the thermally extensible fibers are thermally fused to each other, and the raising of the surface of the non-woven fabric 10 is not easily caused. Whether or not the fibers are thermally fused to each other is judged by scanning electron microscopic observation of the nonwoven fabric 10.

The recess 18 includes a first linear portion 18a that extends in parallel with each other in parallel. Further, the recessed portion 18 includes a second linear portion 18b that extends in parallel with each other so as to intersect the first linear portion. A diamond-shaped portion having a closed shape is formed by the intersection of the two linear portions 18a and 18b. This rhombic portion becomes the convex portion 19. That is, the convex portion 19 is formed by being surrounded by the recess 18 having a continuously closed shape.

Fig. 3 shows a nonwoven fabric 10 of a form different from that shown in Fig. 2(a). The pattern of the non-woven fabric 10-like recessed portion 18 shown in the figure is different from the non-woven fabric shown in Fig. 2(a). However, the structure of the cross section is the same as that of Fig. 2(b). The recessed portion 18 of the non-woven fabric shown in Fig. 3 is formed by crimping or subsequently forming the constituent fibers of the nonwoven fabric 10. The crimp is connected to the bottom. The convex portion 19 is located between the concave portions 18. The crimping and bonding portion refers to a joint portion formed by crimping or structuring the constituent fibers of the nonwoven fabric 10. Examples of the method of crimping the fibers include embossing with or without heat, ultrasonic embossing, and the like. On the other hand, as a method of attaching a fiber, the combination of various adhesive agents is mentioned. In the nonwoven fabric 10, except for the pressure-bonding joint portion, specifically, the projection portion 19, the intersection of the constituent fibers of the nonwoven fabric is joined by a method other than pressure bonding.

The area ratio of the concave portion 18 to the convex portion 19 in the nonwoven fabric 10 is expressed by an embossing ratio (the embossed area ratio, that is, the ratio of the total area of the concave portion 18 to the entire nonwoven fabric 10), and the fluffiness of the non-woven fabric 10 or The intensity has an impact. From these viewpoints, the embossing ratio in the nonwoven fabric 10 is preferably 5% or more and 35% or less, and more preferably 10% or more and 25% or less, in the embodiment shown in Fig. 2(a). In the embodiment shown in Fig. 3, it is preferably 1% or more and 20% or less, and more preferably 2% or more and 10% or less. The embossing rate was measured by the following method. First, the surface magnified photograph of the non-woven fabric 10 is obtained by using the microscope VHX-900 and the lens VH-Z20R manufactured by KEYENCE, and the scale is combined with the enlarged photograph of the surface to measure the size of the concave portion 18 (ie, the embossed portion), and the measurement portion is calculated. The total area of the areas of the recesses 18 in the overall area Q. The embossing rate can be calculated by the calculation formula (P/Q) × 100.

The nonwoven fabric 10 shown in Figs. 2 and 3 contains the thermally extensible fiber of the present invention in a thermally stretched state. In the following description, the thermally extensible fiber in a thermally stretched state is referred to as "fiber after heat elongation". The nonwoven fabric 10 may contain only the fibers after heat elongation, or may be configured to contain not only the fibers after heat elongation but also other fibers, for example, comprising two components having different melting points and being stretched. Non-thermally extensible core-sheath type heat-fused composite fiber. Further, fibers which do not have heat fusion properties (for example, natural fibers such as cotton or pulp, rayon or acetate fibers, etc.) may be contained. In the case where the nonwoven fabric 10 contains not only the fiber after heat elongation but also other fibers, the ratio of the fiber after heat elongation in the nonwoven fabric 10 is preferably 20% by mass or more, particularly preferably 30% by mass or more, and preferably 80%. The mass% or less is more preferably 70% by mass or less. Further, the ratio of the other fibers is preferably 20% by mass or more, more preferably 30% by mass or more, and is preferably 80% by mass or less, and particularly preferably 70% by mass or less.

Since the fiber-based heat-expandable fiber which is contained in the nonwoven fabric 10 is elongated after elongation, the heat-extensible fiber can be thermally extended to a large extent. However, this case does not mean that the fiber cannot be thermally elongated after the thermal elongation contained in the nonwoven fabric 10, and it is known from the following manufacturing method of the nonwoven fabric 10 that it has room for further thermal elongation. That is, the fiber-based heat-extensible fiber is elongated after the heat elongation, and is still thermally extensible.

When the thermally stretched fiber having a room for heat elongation is observed in the thickness direction of the nonwoven fabric 10, the heat elongation differs depending on the position in the thickness direction. Specifically, the thermal elongation of the fiber after the thermal elongation of the second surface 10 b which is a substantially flat surface is higher than that of the fiber after the thermal elongation of the first surface 10 a which is the surface having the uneven surface. In the nonwoven fabric 10, the thermal elongation of the fibers after the thermal elongation in the thickness direction is different, and the elongation of the second surface 10b side is increased when the fibers are thermally stretched by heat treatment by the following heat treatment, and as a result, The bulkiness of the non-woven fabric 10 after the heat treatment becomes very obvious. From the viewpoint of making this advantage more conspicuous, it is preferable that the thermal elongation _C of the fiber after thermal elongation of the position P _C corresponding to the convex portion existing on the surface on the second surface 10b side is present in The ratio (C/D) of the thermal elongation D of the fiber after thermal elongation of the position P _D corresponding to the convex portion on the surface on the first surface 10a side is in the melting point + 20 ° C of the second resin component constituting the heat-expandable fiber. It is 3 or more, more preferably 3 or more and 10 or less, and still more preferably 4 or more and 10 or less. From the same viewpoint, it is preferable that the thermal elongation of the fiber after the thermal elongation gradually increases from the first surface 10a of the nonwoven fabric 10 toward the second surface 10b. In order to set the value of C/D to the above range, for example, the hot air blowing conditions (for example, the temperature of hot air or the wind speed) when the nonwoven fabric 10 is produced by the following method may be appropriately set. The reason why the value of C/D can be set to the above range is that the rate of change in thermal elongation or thermal elongation of the thermally extensible fiber used as the raw material of the nonwoven fabric 10 is within the above range. Therefore, even if the heat-expandable fiber known to date is used as the raw material fiber, the value of C/D cannot be set to the above range.

The thermal elongation of the fiber after thermal elongation contained in the nonwoven fabric 10 was measured by the following method. Five fibers were placed in each of the portions in the thickness direction of the non-woven fabric. The length of the collected fibers is set to be 1 mm or more and 5 mm or less. The collected fibers were clamped in a specimen slide, and the total length of the sandwiched fibers was measured. For the measurement, a microscope VHX-900 manufactured by KEYENCE and a lens VH-Z20R were used. In the measurement, the fibers were observed at a magnification of 50 times or more and 100 times or less, and the observation image was carried out using a measuring tool incorporated in the apparatus. The length obtained by the above measurement is referred to as "the total length of the fiber collected from the nonwoven fabric" Y. The fiber after measuring the full length was placed in a sample container for DSC 6200 manufactured by SII NanoTechnology Co., Ltd. (trade name: robot container 52-023P, 15 μL, aluminum In the system). The container in which the above-mentioned fiber was placed was placed in a sample place in a heating furnace of DSC 6200 which was previously set to a temperature 20 ° C higher than the melting point of the second resin component. After the temperature measured by the thermocouple immediately below the sample placement position of the DSC 6200 (the display name in the measurement software: the sample temperature) is within a range of ±1 ° C higher than the melting point of the second resin component by 20 ° C, After heating for 60 sec, it was quickly taken out. The heat-treated fiber was taken out from the sample container of the DSC, and placed in a specimen slide, and the total length of the sandwiched fiber was measured. For the measurement, a microscope VHX-900 manufactured by KEYENCE and a lens VH-Z20R were used. In the measurement, the fibers were observed at a magnification of 50 times or more and 100 times or less, and the observation image was carried out using a measuring tool incorporated in the apparatus. The length obtained by the above measurement is referred to as "the total length of the fiber after the heat treatment" Z. The thermal elongation (%) was calculated according to the following formula.

Thermal elongation (%) = (Z-Y) ÷ Y × 100 [%]

It is defined as the thermal elongation of fibers taken from a nonwoven fabric. When the thermal elongation is greater than 0, it can be judged that the fiber is thermally extensible.

When the nonwoven fabric 10 is used as a surface sheet such as an absorbent article, the basis weight thereof is preferably 10 g/m ² or more and 80 g/m ² or less, and particularly preferably 15 g/m ² or more and 60 g/m ^{2 .} Hereinafter, it is particularly preferably 20 g/m ² or more and 40 g/m ² or less. When it is used for the same use, the thickness of the nonwoven fabric 10 is preferably 0.5 mm or more and 3 mm or less, more preferably 0.7 mm or more and 3 mm or less in the state after the heat treatment described below. Further, the thickness of the non-woven fabric was measured by the following method.

Next, a description will be given of a preferred manufacturing method for facing the nonwoven fabric 10 with reference to FIG. The apparatus 20 shown in the figure includes a web manufacturing unit 30, an embossed portion 40, and a hot air spraying unit 50. In the fabric manufacturing unit 30, The woven fabric 10a is produced from fibers which are raw materials of the nonwoven fabric 10 (i.e., thermally extensible fibers in a state before stretching and, if necessary, other fibers). The woven fabric 10a has a first surface 101 and a second surface 102 on the opposite side. The second surface 102 is a surface that is in contact with the flat roll 42 in the embossed portion 40 described below, and is attached to the hot air spraying unit 50 described below, and a conveyor belt containing a gas permeable mesh. (conveyer belt) 52 opposite. The first surface 101 is a surface that is in contact with the pattern roll 41 in the embossed portion 40, and is attached to the surface of the hot air spraying unit 50 that is subjected to hot air spraying.

As the fabric manufacturing portion 30, for example, a carding machine 31 as shown in the drawing can be used. Other fabric manufacturing devices, such as air-laid devices, may be used in place of the carding machine 31 depending on the particular application of the nonwoven fabric 10. The woven fabric 10a produced by the carding machine 31 is in a state in which its constituent fibers are loosely entangled with each other, and the shape retaining property as a sheet is not obtained. Therefore, in order to impart the shape retaining property to the woven fabric 10a, the woven fabric 10a is processed in the embossed portion 40 to form the embossed fabric 10b.

The embossed portion 40 includes a pair of rolls 41 and 42 opposed to each other with the woven fabric 10a. The roller 41 is formed of a pattern roll made of a metal having a plurality of irregularities formed on its circumferential surface. The uneven pattern of the pattern roll can be appropriately selected depending on the specific use of the nonwoven fabric 10. For example, in the case of forming a rhombic lattice-shaped embossed pattern shown in FIG. 2(a), a convex portion having a shape corresponding to the rhombic lattice may be formed on the circumferential surface of the roller 41. Moreover, when it is necessary to form the dot-shaped embossing pattern shown in FIG. 3 in the nonwoven fabric 10, the convex part of the shape corresponding to this lattice may be formed in the circumferential surface of the roller 41. On the other hand, the roller 42 contains a smooth roll whose peripheral surface is smooth. The roller 42 is made of metal, rubber, paper or the like.

In the embossing portion 40, the pressing fabric 10a is held by the two rolls 41, 42 to perform embossing. Specifically, the heat-expandable fiber which is a constituent fiber of the woven fabric 10a is pressure-densified by heat densification, and a plurality of embossed portions are formed in the woven fabric 10a to produce the embossed fabric 10b. In the present manufacturing method, the roller 41 and the roller 42 are configured to be heated, and at least the pattern roller 41 is heated to a specific temperature when the embossed portion 40 is operated. The smoothing roller 42 may or may not be heated.

In the embossed portion 40, the pattern roll 41 which is the roll on which the first surface 101 abuts on the surface of the woven fabric 10a is heated in advance, and the temperature is maintained at the melting point or higher of the second resin component in the heat-expandable fiber. The temperature of the melting point of the first resin component. At the same time, the temperature of the smoothing roller 42 which is the roller that the second surface 102 abuts on the surface of the woven fabric 10a is maintained at the melting point of the second resin component in the thermally extensible fiber at -20 ° C or higher and does not reach the melting point of the first resin component. The temperature. The smoothing roller 42 may be used without being heated, and the temperature may be maintained below the melting point of the second resin component, or may be within a temperature not exceeding the melting point of the second resin component. It is used in a state of being heated. The embossed fabric 10b which is surely imparted with shape retaining property can be obtained by setting the temperatures of the two rolls 41, 42 in the above manner.

The heating temperature of the pattern roll 41 is preferably set to Mp (° C.) when the melting point of the second resin component is set so as to impart a high degree of strength and impart a soft touch. It is Mp or more, and more preferably Mp or more and Mp+20 ° C or less. On the other hand, the heating temperature of the smoothing roller 42 is preferably Mp-20 ° C or more and Mp + 20 ° C or less when the melting point of the second resin component is Mp (° C.). By setting the embossed portion to the same temperature range, The material does not exhibit substantial elongation in the thermally extensible fibers. The term "not exhibiting substantial elongation" excludes the intentional elongation of the thermally elongated fibers, and the thermally extensible fibers are inevitably slightly elongated due to variations in the temperature of the embossed portion 40 or the like.

The embossed fabric 10b to which the conformal property is imparted in the treatment of the embossed portion 40 is then transferred to the hot air spraying portion 50. The hot air spraying unit 50 includes a hood 51. The embossed fabric 10b passes through the hood 51. Further, the hot air spraying unit 50 has a conveyor belt 52 containing a gas permeable mesh. The conveyor belt 52 is wrapped around the hood 51. The embossed fabric 10b is placed on the conveyor belt 52 and conveyed in the hot air spraying unit 50. The conveyor belt 52 is formed of a resin such as metal or polyethylene terephthalate.

In the hot air spraying unit 50, hot air is sprayed onto the first surface 101 of the embossed fabric 10b by air through. That is, the hot air spraying unit 50 is configured such that the hot air that is heated to a specific temperature penetrates the embossed fabric 10b. The air circulation processing is performed at a temperature at which the thermally extensible fiber in the embossed fabric 10b is elongated by heating. Further, it is carried out at a temperature at which the thermally extensible fibers in the free state of the portion other than the embossed portion of the embossed fabric 10b are thermally fused to each other. The thermally extensible fiber is elongated by the hot air sprayed at this temperature. The heat-extensible fiber is partially fixed by the joint portion including the embossed portion, so that the stretcher is a portion between the joint portions. Further, a part of the heat-extensible fiber is fixed by the joint portion, whereby the elongation of the elongated fiber is lost to the direction of the plane of the embossed fabric 10b, and is moved in the thickness direction of the embossed fabric 10b. Thereby, the joint portion is swelled to form the convex portion 19, and the nonwoven fabric 10 becomes bulky. Further, it has a three-dimensional appearance in which a plurality of convex portions 19 are formed. and then, The points at which the thermally extensible fibers are joined to each other are joined by fusion. In this manner, the nonwoven fabric 10 having the plurality of irregularities on the first surface 10a and the second surface 10b being substantially flat is obtained.

Preferably, the hot air blowing in the present manufacturing method is terminated by the period in which the thermally extensible fiber is not completely stretched. In addition, as described above, the hot air spray of the air circulation type is performed from the first surface 101 side of the two faces of the embossed fabric 10b. The hot air sprayed on the side of the first surface 101 passes through the embossed fabric 10b, and is discharged from the second surface 102 side. When the hot air is passed through the embossed fabric 10b, the heat is lost and the temperature is lowered. Therefore, the first surface 101 and the second surface 102 of the embossed fabric 10b are heated at different temperatures. Specifically, the second surface 102 side has a lower heating temperature than the first surface 101 side. Therefore, when the embossed fabric 10b is viewed in the thickness direction thereof, the heat-expanded fiber near the first surface 101 and the heat-expanded fiber near the second surface 102 are heated by the heat-extended fiber near the second surface 102. The temperature is lower. As a result, the fiber after the thermal elongation near the second surface 102 is closer to the fiber after the thermal elongation of the first surface 101, and the degree of elongation is small. In other words, the fiber after the thermal elongation near the second surface 102 is closer to the fiber after the thermal elongation of the first surface 101, and there is still room for further thermal elongation. Therefore, in the obtained non-woven fabric 10, it is closer to the second surface 102 of the embossed fabric 10b than the heat-elongated fiber of the first surface 10a which is the surface corresponding to the first surface 101 of the embossed fabric 10b. The thermal elongation of the fiber after the thermal expansion of the second surface 10b is high. For the reason described above, the thermal elongation C of the fiber after the thermal elongation of the position P _C (see FIG. 2( b )) corresponding to the convex portion in the surface on the second surface 10 b side of the nonwoven fabric 10 is greater than that present in the first The thermal elongation _D of the fiber after thermal elongation at the position P _D corresponding to the convex portion in the surface on the one side 10a side.

In order to make the thermal elongation of the fiber after the thermal elongation of the second surface 10b side of the nonwoven fabric 10 larger than the thermal elongation of the fiber after the thermal elongation of the first surface 10a side, the air circulation pattern of the embossed fabric 10b is appropriately adjusted. The temperature or wind speed of the hot air, and the spraying time can be used. The temperature of the hot air is preferably a temperature lower than the melting point of the second resin component by 6 ° C to a temperature higher by 15 ° C and lower than the melting point of the first resin component. On the other hand, the wind speed is preferably set to 0.05 m/sec or more and 10 m/sec or less. When the temperature of the hot air is the same, when the wind speed is small, the difference in the thermal elongation of the fibers after the heat elongation in each of the faces 10a and 10b can be easily increased. On the other hand, when the wind speed is the same, when the temperature of the hot air is set low, the difference in the thermal elongation of the fibers after the heat elongation in each of the faces 10a and 10b can be easily increased. The hot air spray time is preferably, for example, 1 second or longer and 10 seconds or shorter.

Thereby, the nonwoven fabric 10 shown in Fig. 2 or Fig. 3 is obtained. The nonwoven fabric 10 is temporarily taken up and stored in the form of a roll, and then taken out from the roll and used. Alternatively, on the same production line as the manufacturing line of the non-woven fabric 10, the required processing is carried out to manufacture the target product.

The non-woven fabric 10 wound in the state of a roll is often subjected to a reduction in bulkiness due to the winding pressure. Therefore, when the nonwoven fabric 10 is taken out from the roll and used, it is preferable to spray the hot air to the nonwoven fabric 10 by air circulation, and to reduce the fluffy recovery. In the fluffy recovery, as the hot air to be sprayed on the nonwoven fabric 10, it is preferable to use a temperature lower than the melting point of the second resin component in the fiber after heat elongation (the fiber has thermal extensibility as described above) by 6 ° C to 20 ° C higher. Hot air at a temperature that does not reach the melting point of the first resin component.

As a method of recovering the fluffy of such a non-woven fabric, for example, the Japanese Patent Application Laid-Open No. Hei. No. 2004-137655, the Japanese Patent Application Laid-Open No. Hei. No. Hei. Technology.

When the nonwoven fabric 10 is fluffed and recovered by the hot air blowing by the air circulation method, the hot air may be sprayed from the first surface 10a side of the non-woven fabric 10, or the hot air may be sprayed from the second surface 10b side. From the viewpoint of making the fluffy recovery more conspicuous, it is preferable to spray hot air from the side of the second surface 10b.

When the nonwoven fabric 10 is heated and fluffed, the fiber is not only located on the side of the first surface 10a which is the uneven surface of the nonwoven fabric 10, but also the fiber which is stretched after the thermal expansion of the second surface 10b which is a substantially flat surface. Also stretched. The non-woven fabric 10 is different from the first surface 10a side and the second surface 10b side in the case where the thermal elongation of the fibers after thermal expansion is different as described above. Therefore, the non-woven fabric 10 is sprayed with hot air by air circulation. The side of the second surface 10b of the fiber after the thermal elongation, which has a relatively high thermal elongation, clearly exhibits elongation of the fiber after thermal elongation. As a result, as shown in FIG. 5, the nonwoven fabric 10 after the fluffy recovery (hereinafter referred to as the "non-woven fabric 100 after the fluffy recovery") has a plurality of convex portions 109a and concave portions 108a on the side of the first surface 100a. The plurality of convex portions 109b and the concave portions 108b are also provided on the second surface 100b side. When the nonwoven fabric 100 is recovered after the fluffy recovery in the plan view, the convex portion 109a on the first surface 100a side and the convex portion 109b on the second surface 100b side are located at the same position. Similarly, when the non-woven fabric 100 is recovered after the fluffy recovery in the plan view, the concave portion 108a on the first surface 100a side and the concave portion 108b on the second surface 100b side are located at the same position.

In the fluffy recovery non-woven fabric 100 shown in FIG. 5, the first surface 100a corresponds to the first surface 10a of the nonwoven fabric 10 shown in FIGS. 2 and 3. Further, the second surface 100b of the non-woven fabric 100 after the fluffy recovery corresponds to the second surface 10b of the nonwoven fabric 10 shown in Figs. 2 and 3 . The degree of unevenness on the side of the first surface 100a of the uneven surface structure 100a and 100b of the non-woven fabric 100 after the fluffy recovery is higher than that of the second surface 100b side. In other words, the height difference of the unevenness is increased, and the thickness of the convex portion 109a on the first surface 100a side based on the thickness direction center position L of the nonwoven fabric 100 after the fluffy recovery is larger than the thickness of the convex portion 109b on the second surface 100b side. In the non-woven fabric 10 before the fluffy recovery, the second surface 10b side is substantially flat. Therefore, it is considered that the thickness of the second surface 100b side of the nonwoven fabric 100 after the fluffy recovery is caused by the thermal elongation of the nonwoven fabric 10 on the second surface 10b side. The thermal elongation of the fibers. After the fluffy recovery, the center position L of the thickness direction of the non-woven fabric 100 is obtained by using the microscope VHX-900 and the lens VH-Z20R manufactured by KEYENCE to obtain a magnified photograph of the non-woven fabric cross section of the non-woven fabric 100 after the fluffy recovery, and the adjacent concave portions are connected by a straight line. And decided.

At the time of focusing on the non-woven fabric of the second surface 100 after the bulk recovery projecting portion 109b 100B, the thickness of the projecting portion 109b of T _b nonwoven thickness direction of the central position 100 after to the bulk recovery L as a reference, preferably with respect to loft the reply The thickness of the non-woven fabric 100 accounts for 20% or more and 40% or less, more preferably 22% or more and 35% or less. On the other hand, the thickness T _a of the convex portion 109a of the first surface 100a of the nonwoven fabric 100 after the fluffy recovery is based on the center position L in the thickness direction, and preferably 60% or more and 80% or less of the thickness of the nonwoven fabric 100 after the fluffy recovery. More preferably, it accounts for 65% or more and 78% or less. As a result, the non-woven fabric 100 after the fluffy recovery has a concave and convex structure on both sides, and thus has a high-contrast style.

The fiber after being subjected to the heat elongation in the non-woven fabric 100 after the fluffy recovery is elongated by the hot air blowing when the fluffy is recovered, but this does not mean that the fiber is not completely imparted by the heat after the heat elongation. elongation. That is, the fiber which is contained in the nonwoven fabric 100 after the fluffy recovery can be further elongated by the imparting of heat. However, since the fiber which is included in the non-woven fabric 100 after the fluffy recovery is subjected to the heat application twice, the degree of heat is not large even if it is thermally extensible. Specifically, the thermal elongation _E of the fiber after the thermal elongation at the position P _E corresponding to the convex portion 109 b on the surface on the second surface 100 b side corresponds to the convex portion 109 a on the surface existing on the first surface 100 a side. The ratio (E/F) of the thermal elongation F of the fiber after the thermal elongation of the position P _F is preferably from 0.1 or more to less than 3 in the melting point of the second resin component constituting the fiber after thermal elongation + 20 ° C, more preferably It is 2.0 or more and 2.8 or less. The thermal elongation of the fiber after the thermal elongation contained in the nonwoven fabric 100 after the fluffy recovery is measured by the same method as the thermal elongation of the fiber after the thermal elongation contained in the nonwoven fabric 10.

The non-woven fabric 10 and the fluffy recovery after the fluffy recovery thereof can be preferably used as a constituent member of various absorbent articles such as a sanitary napkin or a disposable diaper, for example, a surface sheet or the like. Further, in addition to the use, it can be preferably used as, for example, a second sheet (a sheet disposed between the surface sheet and the absorbent body), a back sheet, a leak-proof sheet, or a wiper for human use. A sheet for skin care, skin care, and the like. When the non-woven fabric 10 and the fluffy recovery are used for the absorbent article such as menstrual sanitary napkins, the non-woven fabric 10 and the fluffy recovery back surface of the non-woven fabric 100 having the convex portions and the concave portions are disposed toward the wearer's skin. Absorb Physically.

In the above embodiment, the present invention further discloses the following thermally extensible fiber, a method for producing the same, and a nonwoven fabric.

<1> A heat-expandable fiber comprising a first resin component and a second resin component having a melting point or a softening point lower than a melting point of the first resin component, wherein the second resin component continuously exists on the fiber surface in the longitudinal direction At least a portion thereof, and elongated in length due to heating, and The rate of change of the thermal elongation B at the melting point of the second resin component + 10 ° C with respect to the thermal elongation A of the melting point of the second resin component at -6 ° C ({(BA) / A} × 100) is 130% or more .

<2> The heat-expandable fiber according to the above <1>, wherein the melting point of the second resin component + the thermal elongation B at 10 ° C is changed with respect to the thermal elongation A of the second resin component at a melting point of -6 ° C. The rate ({(BA)/A}×100) is 130% or more and 300% or less.

<3> The thermally extensible fiber according to the above <1> or <2>, wherein the melting point of the second resin component + the thermal elongation B at 10 ° C is higher than the melting point of the second resin component at -6 ° C The rate of change of the rate A ({(BA)/A}×100) is 135% or more and 210% or less.

The thermally extensible fiber according to any one of the above items <1> to <3> wherein the thermal elongation A is 3.5% or less.

<5> The heat-expandable fiber according to the above <4>, wherein the thermal elongation A is 0% or more and 3.5% or less, particularly preferably 0% or more and 3.2% or less, particularly preferably 0% or more and 3.0% or less.

<6> The heat-extensible fiber according to any one of the above <1> to <5>, wherein the first The resin component contains polylactic acid, and the second resin component contains polyolefin.

The thermally extensible fiber according to any one of the above-mentioned items, wherein the first resin component and the second resin component are preferably a first resin component: a second resin component = 20: 80 to 80:20, more preferably 30:70 to 70:30.

The heat-expandable fiber according to any one of the above-mentioned items, wherein the first resin component contains polylactic acid, and the polylactic acid has a melt index of 2 g/10 min or more and 50 g/10 Below min, especially below 5 g/10 min and below 40 g/10 min.

The heat-expandable fiber according to any one of the above-mentioned <1>, wherein the first resin component contains polylactic acid, and the first resin component containing the polylactic acid has an orientation index of 3% or more and 50%. Hereinafter, it is preferably 10% or more and 40% or less.

The thermally extensible fiber of any one of the above-mentioned <1> to <9>, wherein the second resin component contains a polyolefin, and the polyolefin contains polyethylene.

The thermally extensible fiber according to any one of the above-mentioned <1>, wherein the second resin component comprises a polyolefin, and the polyolefin contains polyethylene, and the polyethylene has a melt index of 10 g/10 Above 40 g/10 min below min, especially below 10 g/10 min and 25 g/10 min.

The thermally extensible fiber according to any one of the above-mentioned items, wherein the second resin component comprises a polyolefin, and the polyolefin contains polyethylene, and the polyethylene has an orientation index of 5% or more. It is preferably 8% or more.

(13) The heat-expandable fiber according to any one of the above-mentioned items, wherein the ratio of the crimping ratio (%) measured in accordance with JIS L1015 to the number of crimps measured according to JIS L1015 (a) The crimping rate (%) / the number of crimps (a) is 0.45 or more and 0.75 Hereinafter, it is preferably 0.50 or more and 0.70 or less.

<14> A non-woven fabric using the heat-expandable fiber according to any one of the above items <1> to <13>, which has a plurality of convex portions and concave portions on one surface side, and the other surface side is flatter than the one surface side. The heat-extensible fiber in a state of thermal elongation is contained in the convex portion, and The thermal elongation C of the thermally extensible fiber in a thermally stretched state at a position corresponding to the convex portion on the surface of the other surface side, and the thermal elongation state of the thermally extensible state at a position corresponding to the convex portion on the surface on one side The ratio (C/D) of the thermal elongation D of the fiber is 3 or more at the melting point + 20 ° C of the second resin component constituting the thermally extensible fiber.

<15> The non-woven fabric according to <14> above, wherein the convex portion is filled with a constituent fiber of the nonwoven fabric.

<16> A non-woven fabric using the heat-expandable fiber according to any one of the above items <1> to <13>, wherein the non-woven fabric has a plurality of convex portions and concave portions on one surface side, and also has a plurality of convex portions and concave portions on one surface side. a plurality of convex portions and concave portions, the convex portion and the concave portion on one surface side and the convex portion and the concave portion on the other surface side are located at the same position in a plan view of the non-woven fabric, and the heat-extensible fiber containing the thermally stretched state in the convex portion exists on the other side The thermal elongation E of the thermally extensible fiber in a thermally stretched state at a position corresponding to the convex portion on the surface of the side, and the heat of the thermally extensible fiber in a thermally stretched state at a position corresponding to the convex portion on the surface on one side The ratio (E/F) of the elongation F is 0.1 or more and less than 3 at the melting point +20 ° C of the second resin component constituting the thermally extensible fiber, and In the convex portion, the thickness of the convex portion on the other surface side based on the center position in the thickness direction of the non-woven fabric accounts for 20% or more and 40% or less of the thickness of the entire convex portion.

<17> A method for producing a heat-expandable fiber, wherein the spinning temperature of the first component is set to a melting point of the first component plus a range of from 20 ° C to 180 ° C, and the spinning temperature of the second resin component is set to The melting point of the two components is in the range of from 20 ° C to 180 ° C, and is melt-spun at a spinning speed of from 50 m/min to 1500 m/min, and is subjected to crimping without stretching, and thereafter, at 100. Relaxation treatment by heating and drying at a temperature above 125 °C.

<18> The method for producing a heat-expandable fiber according to the above <17>, wherein the spinning temperature of the first component is set to a melting point of the first component plus a range of 70 ° C to 170 ° C, and the second resin component is The spinning temperature is set to a range in which the melting point of the second component is 100 ° C or more and 170 ° C or less.

<19> The method for producing a heat-expandable fiber according to the above <17>, wherein the spinning temperature of the first component is set to a range of 230 ° C to 250 ° C, and the second resin component is spun. The temperature is set to a range of 240 ° C or more and 280 ° C or less.

The method for producing a thermally extensible fiber according to any one of the above-mentioned items, wherein the spinning speed is from 100 m/min to 1400 m/min, and melt spinning is performed.

<21> Manufacture of heat-expandable fiber according to any one of <17> to <20> above In the method, the above-described heat drying relaxation treatment is carried out at 110 ° C or more and 120 ° C or less.

Example

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the invention is not limited by the embodiment.

[Example 1] (1) Manufacture of heat-extensible fibers

The heat-expandable fiber containing the concentric core-sheath type composite fiber was produced by the melt spinning method using the apparatus described in FIG. 1 of the patent document 1. Polylactic acid (PLA) having a melt index of 8 g/10 min was used as the first resin component. High density polyethylene (HDPE, High Density Polyethylene) having a melt index of 22 g/10 min was used as the second resin component. The first resin component and the second resin component were melt-spun at a spinning temperature and a spinning speed shown in Table 1 below. Further, after melt spinning, the subsequent treatment shown in the table was performed. A heat-extensible fiber containing short fibers having a fiber length of 51 mm was obtained. For the heat-expandable fiber, various physical properties were measured as described above. The results are shown in Table 1 below.

(2) Preparation of heat fusible fiber

A heat-fusible fiber containing concentric core-sheath type composite fibers shown in Table 2 below was prepared.

(3) Manufacture of non-woven fabrics

The non-woven fabric 10 of the single-layer structure shown in Fig. 2 was produced by using the apparatus shown in Fig. 4 in accordance with the mass ratio shown in Table 3 using the heat-expandable fiber and the heat-fusible fiber. The pattern roll 41 in the apparatus shown in Fig. 4 has a line width of 0.5 mm a lattice-shaped convex portion. The area ratio of the convex portion of the pattern roller 41 is 14%. Further, the production was carried out under the conditions shown in Table 3 below to obtain a nonwoven fabric 10. In the obtained non-woven fabric 10, the fibers after the elongation are fused to each other. The intersection of the fiber and the heat-fusible fiber after heat elongation is also fused. Further, the intersections of the heat-fusible fibers are also fused. For the obtained non-woven fabric, various evaluations were carried out by the following methods. The results are shown in Table 3.

[thickness]

The thickness of the nonwoven fabric 10 is measured by observing the longitudinal section of the nonwoven fabric. First, the non-woven fabric was cut into the size of MD 120 mm × CD 60 mm, and the measurement piece was taken. A 12.5 g (56.4 mm diameter) metal plate was placed on the test piece, and a load of 49 Pa was applied. In this state, the longitudinal section of the nonwoven fabric was observed with a microscope (manufactured by KEYENCE Co., Ltd., VHX-900, lens VH-Z20R), and the thickness of the convex portion of the nonwoven fabric was measured.

[base weigh]

The non-woven fabric 10 was cut into MD 120 mm × CD 60 mm to produce a cut piece. The basis weight was calculated by measuring the weight of the cut piece by an electronic balance.

(4) fluffy reply of non-woven fabric

The non-woven fabric 10 obtained in the above item (3) is placed on a hammer or the like so as to be pressurized at a pressure of 4.9 kPa, and is allowed to stand in an environment of 50 ° C for 10 days (240 hours) to reduce the thickness and bulkiness. The non-woven fabric 10 was sprayed with hot air in an air circulation mode under the conditions shown in Table 4 to make the fluffy return, and the non-woven fabric 100 was obtained after the fluffy recovery. The obtained nonwoven fabric 100 after the fluffy recovery has the structure shown in FIG. The nonwoven fabric 100 after the fluffy recovery was subjected to various evaluations by the following methods. The results are shown in Table 4.

[Thickness of convex portion on the second surface side]

The thickness of the non-woven fabric 100 after the fluffy recovery and the thickness of the non-woven fabric 10 were measured by the same method. The thickness of the convex portion on the second surface side of the nonwoven fabric 100 after the fluffy recovery was measured as follows. First, as described above, an enlarged photograph of the non-woven fabric cross-section of the nonwoven fabric 100 after the fluffy recovery is obtained, and the center position L in the thickness direction is obtained by connecting the adjacent concave portions in a straight line. Then, the center line L in the thickness direction of the straight line is drawn to the apex of the convex portion on the second surface side, and the distance from the center position L in the thickness direction on the perpendicular line to the vertex is defined as the convex surface on the second surface side. The thickness of the department.

[texture]

Place the non-woven fabric on the flat table with the convex parts facing up. For the observation group of five people, the degree of texture when the non-woven fabric was observed from above was evaluated according to the following four criteria. The results are expressed as an average of 5 people.

<Judgement criteria>

4: The texture of non-woven fabric is excellent.

3: The texture of the non-woven fabric is better.

2: The texture of non-woven fabric is slightly worse.

1: The texture of non-woven fabric is poor.

<evaluation result>

B: The average value is judged to be 3.0 or more and 4.0 or less.

C: The average is 2.0 or less and less than 3.0.

D: The average is 1.0 or more and less than 2.0.

[concave feeling]

The unevenness of the non-woven fabric 100 is measured by observing the longitudinal section of the non-woven fabric set. First, the non-woven fabric was cut into the size of MD 120 mm × CD 60 mm, and the measurement piece was taken. A 12.5 g (56.4 mm diameter) metal plate was placed on the test piece, and a load of 49 Pa was applied. In this state, the longitudinal section of the nonwoven fabric was observed using a microscope VHX-900 manufactured by KEYENCE and a lens VH-Z20R. For the observation group of five people, the degree of unevenness of the non-woven fabric was evaluated according to the following four criteria. The results are expressed as an average of 5 people.

<Judgement criteria>

4: Non-woven fabric is full of unevenness.

3: Non-woven fabric has a concave and convex feeling.

2: Non-woven fabric lacks concavity.

1: No weaving has no unevenness.

<evaluation result>

A: The average value is judged to be 3.0 or more and 4.0 or less.

B: The average is less than 2.5 and less than 3.0.

C: The average is less than 2.0 and less than 2.5.

D: The average is 1.0 or more and less than 2.0.

[fluffy resilience]

A non-woven fabric having a length of 2,700 m was wound in a roll form on a paper tube having an outer diameter of 85 mm, and stored at room temperature for 2 weeks. In the range of the winding diameter of more than 500 mm and less than 600 mm, the non-woven fabric in the wound state after the storage is taken out at a conveying speed of 150 m/min, because the hot air temperature is 139 ° C, and the hot air spraying time is 0.35. The non-woven fabric was sprayed with hot air at a speed of 3.5 m/sec in seconds, and the thickness of the non-woven fabric was restored. Fluffy resilience of non-woven fabric The thickness (pre-storage thickness) of the convex portion of the non-woven fabric before the non-woven fabric is wound into a roll shape is G, and the thickness (recovery thickness) of the non-woven fabric after the hot air is sprayed is expressed by the following formula. The measurement of the thickness of the non-woven fabric after the hot air spraying is performed after 1 minute to 1 hour from the hot air blowing. The thickness of the nonwoven fabric was measured by the method described previously.

Fluffy recovery (%) = H / G × 100

The higher the value of the fluffy recovery property calculated by the above formula, the higher the evaluation.

[Example 2 and Comparative Examples 1 to 4]

The heat-extensible fiber, the nonwoven fabric 10, and the fluffy recovered nonwoven fabric 100 were obtained in the same manner as in Example 1 except that the conditions shown in Tables 1 to 4 below were employed. The results of these evaluations are shown in Tables 1, 3 and 4.

As is known from the results shown in Table 1, it was judged that the heat-expandable fiber-based second resin component obtained in each Example had a low thermal elongation at a melting point of -6 ° C, and the elongation was suppressed. Further, it was judged that the rate of change in the thermal elongation of the heat-expandable fiber obtained in each of the examples was high. On the other hand, it was judged that the fiber-based second resin component obtained in each of the comparative examples had a high thermal elongation at a melting point of -6 ° C or a heat shrinkage, and the rate of change in the thermal elongation was low.

Further, as is known from the results shown in Table 3, it was judged that the nonwoven fabric 10 obtained in each of the examples was the same as the basis weight of the nonwoven fabric obtained in each of the comparative examples, but the thickness was larger than in each of the comparative examples. Obtained non-woven.

Further, as is known from the results shown in Table 4, it was judged that if the non-woven fabric 10 obtained in each of the examples was returned to be fluffy, the fluffy reply was compared with the case where the non-woven fabric obtained in each comparative example was fluffy. The degree is large and the texture or unevenness is good.

[Industrial availability]

According to the present invention, there is provided a heat-extensible fiber in which elongation is suppressed before reaching a certain temperature, and if the degree of elongation exceeds a certain temperature, the degree of elongation is rapidly increased.

10‧‧‧ Non-woven

10a‧‧‧1st

10b‧‧‧2nd

18‧‧‧ recess

18a‧‧‧1st line

18b‧‧‧2nd line

19‧‧‧ convex

20‧‧‧ device

30‧‧‧The Fabric Manufacturing Department

31‧‧‧Card machine

40‧‧‧ embossing processing department

41‧‧‧pattern roll

42‧‧‧Smooth roller

50‧‧‧Hot air spray department

51‧‧‧Exhaust hood

52‧‧‧Conveyor belt

100‧‧‧ Non-woven after fluffy reply

100a‧‧‧1st

100b‧‧‧2nd

101‧‧‧1st

102‧‧‧2nd

108a‧‧‧ recess

108b‧‧‧ recess

109a‧‧‧ convex

109b‧‧‧ convex

A‧‧‧Thermal extensible fiber of the invention

B‧‧‧Previous thermal elongation fibers

L1‧‧‧ line

L2‧‧‧ line

P _C ‧‧‧ position

P _D ‧‧‧Location

P _E ‧‧‧Location

P _F ‧‧‧ position

T1‧‧‧ temperature

Fig. 1 is a graph showing the relationship between the heating temperature and the elongation of the thermally extensible fiber.

Fig. 2 (a) is a perspective view showing an embodiment of the nonwoven fabric of the present invention, and Fig. 2 (b) is a longitudinal sectional view showing the nonwoven fabric shown in Fig. 2 (a).

Figure 3 is a perspective view showing another embodiment of the nonwoven fabric of the present invention (phase As shown in Figure 2 (a)).

Figure 4 is a schematic view showing an apparatus suitable for use in the manufacture of nonwoven fabrics of the present invention.

Fig. 5 is a longitudinal sectional view showing a state in which the nonwoven fabric of the present invention is restored to a fluffy state.

A‧‧‧Thermal extensible fiber of the invention

B‧‧‧Previous thermal elongation fibers

L1‧‧‧ line

L2‧‧‧ line

T1‧‧‧ temperature

Claims (21)

A heat-expandable fiber comprising a first resin component and a second resin component having a melting point or a softening point lower than a melting point of the first resin component, wherein the second resin component continuously exists on the fiber surface continuously in the longitudinal direction A part of the length of the resin component is elongated by heating, and the melting point of the second resin component + the rate of change of the thermal elongation B at 10 ° C with respect to the melting point of the second resin component at -6 ° C ({(BA)) /A}×100) is 130% or more. The heat-expandable fiber of claim 1, wherein the melting point of the second resin component + the rate of change of the thermal elongation B at 10 ° C with respect to the melting point of the second resin component at a temperature of -6 ° C ({( BA)/A}×100) is 130% or more and 300% or less. The thermally extensible fiber according to claim 1 or 2, wherein a melting point of the second resin component + a rate of change of the thermal elongation B at 10 ° C with respect to a thermal elongation A of the second resin component at a melting point of -6 ° C ( {(BA)/A}×100) is 135% or more and 210% or less. The heat-extensible fiber of claim 1 or 2, wherein the heat elongation A is 3.5% or less. The heat-expandable fiber of claim 4, wherein the heat elongation A is 0% or more and 3.5% or less. The thermally extensible fiber of claim 1 or 2, wherein the first resin component comprises polylactic acid and the second resin component comprises polyolefin. The thermally extensible fiber according to claim 1 or 2, wherein a mass ratio of the first resin component to the second resin component is a first resin component: a second resin component =20:80 to 80:20. The heat-expandable fiber according to claim 1 or 2, wherein the first resin component contains polylactic acid, and the polylactic acid has a melt index of 2 g/10 min or more and 50 g/10 min or less. The thermally extensible fiber according to claim 1 or 2, wherein the first resin component contains polylactic acid, and the first resin component containing the polylactic acid has an alignment index of 3% or more and 50% or less. The thermally extensible fiber of claim 1 or 2, wherein the second resin component comprises a polyolefin, and the polyolefin comprises polyethylene. The thermally extensible fiber according to claim 1 or 2, wherein the second resin component comprises a polyolefin, and the polyolefin contains polyethylene, and the polyethylene has a melt index of 10 g/10 min or more and 40 g/10 min or less. The thermally extensible fiber according to claim 1 or 2, wherein the second resin component comprises a polyolefin, and the polyolefin contains polyethylene, and the polyethylene has an orientation index of 5% or more. The heat-extensible fiber according to claim 1 or 2, wherein the ratio of the crimp ratio (%) measured according to JIS L1015 to the number of crimps measured according to JIS L1015 (volume ratio (%) / number of crimps ( ())) is 0.45 or more and 0.75 or less. A non-woven fabric using the heat-extensible fiber of claim 1 as a raw material, having a plurality of convex portions and concave portions on one surface side, and the other surface side being flatter than one surface side, wherein the convex portion contains the thermal elongation state in a heat-extended state Thermal fiber, and the thermal elongation C of the thermally extensible fiber in a state of thermal elongation at a position corresponding to the convex portion on the surface of the other surface side and the surface present on one side The ratio (C/D) of the thermal elongation D of the thermally extensible fiber in the thermally stretched state at the position corresponding to the convex portion in the surface is 3 or more at the melting point + 20 ° C of the second resin component constituting the thermally extensible fiber. The non-woven fabric of claim 14, wherein the convex portion is filled with the constituent fibers of the non-woven fabric. A non-woven fabric using the heat-extensible fiber of claim 1 as a raw material, wherein the non-woven fabric has a plurality of convex portions and concave portions on one side, and has a plurality of convex portions and concave portions on one side, and convex portions on one side. And the concave portion and the convex portion and the concave portion on the other surface side are located at the same position in the plan view of the nonwoven fabric, and the heat-extensible fiber in the heat-extended state is formed in the convex portion, and the heat is present in the surface on the other surface side corresponding to the convex portion. The ratio of the thermal elongation E of the thermally extensible fiber in the stretched state to the thermal elongation F of the thermally extensible fiber in the thermally stretched state at the position corresponding to the convex portion on the one surface side (E/F) The melting point of the second resin component of the thermally extensible fiber is 0.1 or more and less than 3 at 20 ° C. In the convex portion, the thickness of the convex portion in the other surface side based on the center position in the thickness direction of the non-woven fabric occupies the convex portion. The overall thickness is 20% or more and 40% or less. A method for producing a thermally extensible fiber, wherein a spinning temperature of the first component is set to a melting point of the first component plus a range of from 20 ° C to 180 ° C, and a spinning temperature of the second resin component is set to a second component The melting point is increased by 20 ° C or more and 180 ° C or less. Melt spinning is carried out at a spinning speed of 50 m/min or more and 1500 m/min or less, and is subjected to a crimping treatment without stretching, and thereafter, a relaxation treatment by heating and drying at 100 ° C or more and 125 ° C or less is performed. The method for producing a heat-expandable fiber according to claim 17, wherein the spinning temperature of the first component is set to a melting point of the first component plus a range of 70 ° C to 170 ° C, and the spinning temperature of the second resin component is set. The melting point of the second component is added in a range of from 100 ° C to 170 ° C. The method for producing a thermally extensible fiber according to claim 17 or 18, wherein the spinning temperature of the first component is set to a range of 230 ° C to 250 ° C, and the spinning temperature of the second resin component is set to 240 ° C or higher. Below 280 ° C. The method for producing a thermally extensible fiber according to claim 17 or 18, wherein the spinning is carried out at a spinning speed of from 100 m/min to 1400 m/min. The method for producing a heat-expandable fiber according to claim 17 or 18, wherein the heat-drying relaxation treatment is carried out at 110 ° C or more and 120 ° C or less.