JP6611969B2 - Composite fiber, nonwoven fabric and absorbent article sheet - Google Patents

Description

  The present invention relates to a composite fiber, a nonwoven fabric, and a sheet for absorbent articles.

  Absorbent articles for absorbing human or animal menstrual blood, vaginal discharge, urine, feces, and other discharges or excretion (hereinafter collectively referred to as “excretions”) contact the skin The sheet generally has a sheet called a top sheet or a top sheet, and the top sheet is often provided in the form of a nonwoven fabric. Since the surface sheet directly touches the skin, the tactile sensation is emphasized, and generally a smooth and soft tactile sensation is required. In addition, for the surface sheet, the property of quickly transferring the liquid contained in the excrement to the absorber, that is, excellent liquid permeability, and the property of making it difficult to recognize the color of the liquid transferred to the absorber, that is, concealment It is also required to have excellent properties.

  In order to improve one or more of these characteristics or functions, the present applicant has proposed various nonwoven fabrics suitable for constituting the surface sheet or synthetic fibers for constituting the nonwoven fabric. For example, Patent Document 1 proposes a composite fiber having a multi-leaf cross-sectional shape of the core component in order to improve the concealability of the nonwoven fabric, and Patent Document 2 can provide a nonwoven fabric having a bulky and excellent tactile sensation. A composite fiber with excellent crimp development was proposed. Moreover, in patent document 3, the hydrophilic fiber with little irritation | stimulation to skin which made the fiber processing agent containing a specific three component adhere is proposed.

Japanese Patent Laid-Open No. 10-140422 International Publication No. 2012/105602 JP2013-155467A

  For the surface sheet constituting the absorbent article, both higher liquid permeability and better tactile sensation are always desired. The present invention has been made for the purpose of providing a composite fiber capable of providing a nonwoven fabric with good tactile sensation even when the fineness is increased.

In the first aspect, the present invention includes a first component made of a thermoplastic resin, and a second component made of a thermoplastic resin having a melting point after spinning higher than the melting point of the first component after spinning,
In a cross section cut along a plane perpendicular to the length direction, the first component constitutes a sheath that occupies the entire fiber surface, and the second component has a plurality of convex portions in the cross-sectional shape. Configure the leaf-shaped core,
At least one of the convex portions has a maximum width from the convex portion base to the tip, and has a (convex length) / (fiber radius) of 0.68 or more and 0.95 or less.
A core-sheath type composite fiber is provided.

The present invention includes, in the second aspect, a first component made of a thermoplastic resin and a second component made of a thermoplastic resin having a post-spinning melting point higher than the melting point of the first component after spinning,
In a cross section cut along a plane perpendicular to the length direction, the first component constitutes a sheath that occupies the entire fiber surface, and the second component has a plurality of convex portions in the cross-sectional shape. A leaf-shaped core and one or more drops, petals, ginkgo leaves, citrus tufts, fan-shaped or elliptical deformed cores,
At least one of the deformed core portions has a maximum width from the base to the tip of the deformed core portion, and (deformed core length) / (fiber radius) of 0.68 or more and 0.95 or less. Have
A core-sheath type composite fiber is provided.

  The composite fiber of the present invention has a multi-leaf shaped core, or has a multi-leaf shaped core and a deformed core, and is easily deformable, and the sheath component has a small thickness. And the area of the thermal bonding point is relatively small when the sheath component is a thermal bonding component. Due to this feature, the conjugate fiber of the present invention can provide a soft and smooth tactile nonwoven fabric suitable for a surface sheet of an absorbent article.

(A) And (b) is sectional drawing of the composite fiber which respectively concerns on the 1st Embodiment of this invention, (c) is the minimum thickness and the maximum thickness of the 1st component in the cross section shown to (a) It is a schematic diagram which shows thickness and the minimum thickness of a 2nd component. It is a schematic diagram explaining how to obtain the center of the multileaf core of the core-sheath type composite fiber. (A) thru | or (c) are sectional drawings of the composite fiber which concerns on the 2nd Embodiment of this invention, respectively. It is a schematic diagram which shows the base part of the deformed core part of the composite fiber which concerns on the 2nd Embodiment of this invention, a front-end | tip, and the deformed core part length. It is sectional drawing of the composite fiber of a comparative example.

(Background to the present embodiment)
In general, a surface sheet made of a nonwoven fabric tends to have a softer and smoother touch as the fineness of the constituent fiber is smaller, and the liquid permeability tends to be improved as the fineness of the constituent fiber is larger. That is, tactile sensation and liquid permeability are in a trade-off relationship, and the fineness of the fibers constituting the nonwoven fabric is determined so as to obtain a predetermined tactile sensation and liquid permeability according to the use and function of the product. Moreover, when the nonwoven fabric is a heat-bonded nonwoven fabric, the tactile sensation of the nonwoven fabric is also affected by the form of the heat-bonded portion.

  The inventors of the present invention have studied a configuration that can provide a nonwoven fabric having good tactile sensation and excellent liquid permeability with respect to the core-sheath type composite fiber that can also be used as a heat-adhesive fiber. And, the present inventors, the ease of deformation of the fiber affects the flexibility and the like of the nonwoven fabric, if the shape of the core portion is selected so that the deformation of the fiber is likely to occur, even if the fineness is increased, We thought that the nonwoven fabric would be flexible. Furthermore, the present inventors selected the shape of the core part so that the sheath component becomes thin in a part of the fiber cross section, and when the heat-bonded nonwoven fabric was produced by thermally bonding the fibers to each other by heat treatment, It was considered that these fibers were thermally bonded at a thin portion of the sheath component to form a heat-bonding portion having a relatively small bonding area (a heat-bonding portion having a small bonding area is also referred to as a point bonding portion). A heat-bonded part with a large bonding area deteriorates the tactile sensation, for example, gives a strong feeling of friction to the skin or causes a rough texture. If many are formed, the nonwoven fabric becomes soft and smooth. And the core part has a multi-leaf shape having three or more convex parts, and it is easy to deform by reducing the area of the part where each convex part base is gathered, and the sheath component near the tip part of the convex part The present inventors have found that a core-sheath type composite fiber capable of giving a soft tactile sensation can be obtained even when the thickness of the fiber is reduced and the fineness is increased. Hereinafter, this embodiment will be described.

(First embodiment (core-sheath type composite fiber))
The core-sheath-type conjugate fiber of this embodiment includes a first component made of a thermoplastic resin, and a second component made of a thermoplastic resin having a melting point after spinning higher than the melting point after spinning of the first component, The first component is a sheath portion, the second component is a core portion, and in the cross section, the second component is a multileaf shape having three or more convex portions, and at least one of the convex portions is It has the maximum width from the base of the convex part to the tip, and has a (convex part length) / (fiber radius) of 0.68 or more and 0.95 or less. In this composite fiber, the area at the center of the core where the convex bases are gathered is small, which makes it easier for the composite fiber to deform, and it is assumed that the nonwoven fabric produced using this will give a soft touch Is done.

  The core-sheath type composite fiber of this embodiment contains the 1st component which consists of a thermoplastic resin, and the 2nd component which consists of a thermoplastic resin which has a melting point after spinning higher than the melting point after the spinning of a 1st component. The first component can also be referred to as a low melting point component, and the second component can also be referred to as a high melting point component. The fiber of this embodiment is good also as a heat bondable composite fiber in which a 1st component functions as a heat bond component. In that case, a 2nd component maintains a fiber form in the nonwoven fabric after a heat bonding process, and ensures the mechanical characteristic of a nonwoven fabric.

  The melting point of the second component after spinning is preferably 10 ° C. or higher, preferably 20 ° C. or higher, more preferably 25 ° C. or higher than the melting point of the first component after spinning. The melting points of the first component and the second component can be determined from the heat of fusion curve obtained by DSC. Two or more peaks may appear in the heat of fusion curve. In that case, the temperature showing the maximum peak is taken as the melting peak temperature, that is, the melting point. In general, the melting point relationship of the thermoplastic resin before spinning is almost the same as the melting point relationship of the thermoplastic resin after spinning. That is, when the melting point of the second component before spinning is higher than that of the first component, the melting point of the second component after spinning is generally higher than that of the first component. Therefore, the thermoplastic resin constituting the first component and the second component may be selected in consideration of the melting point before spinning.

  As described above, the thermoplastic resin used in the present embodiment is not particularly limited as long as the melting point after spinning of the second component is higher than the melting point after spinning of the first component, and is a known thermoplastic resin. Can be used. For example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and copolymers thereof; low density polyethylene, medium density polyethylene, high density polyethylene, linear Polyethylene resins such as low-density polyethylene and ultra-high molecular weight polyethylene, polypropylene resins such as isotactic, atactic and syndiotactic polymerized using ordinary Ziegler-Natta catalysts and metallocene catalysts, Various polyolefin resins such as methylpentene resin, ethylene-vinyl alcohol copolymer resin, ethylene-propylene copolymer resin; nylon 6, nylon 66, nylon 11, nylon 12, etc. Polyamide resins; polycarbonate, polyacetal, polystyrene, engineering plastics such as cyclic polyolefins can be used. The fiber of this embodiment consists of the 1st component containing 1 or 2 or more resin selected from these resin, and the 2nd component containing 1 or 2 or more resin selected from these resin.

  As a combination of the first component and the second component, for example, a combination of polyethylene resin / polyester resin and polyethylene resin / polypropylene resin can be mentioned. Specifically, high-density polyethylene / polyethylene terephthalate, Low density polyethylene / polyethylene terephthalate, linear low density polyethylene / polyethylene terephthalate, ethylene-propylene copolymer / polyethylene terephthalate, polypropylene / polyethylene terephthalate, high density polyethylene / polytrimethylene terephthalate, low density polyethylene / polytrimethylene terephthalate, Linear low density polyethylene / polytrimethylene terephthalate, ethylene-propylene copolymer / polytrimethylene terephthalate, polypropylene / Polytrimethylene terephthalate, may be mentioned high-density polyethylene / polypropylene.

  In the present embodiment, the second component has a multi-leaf shape having three or more convex portions in the cross section. In a multi-leaf shape having three or more convex portions, the area of the portion where each convex portion base portion gathers is reduced, and the core portion is adjusted so that (convex length) / (fiber radius) is within the above range. It becomes easy to design. The number of convex portions may be 8 or less, and preferably 6 or less. If the number of convex portions is too large, it is difficult to reduce the area of the portion where the convex base portions gather, and a core portion having (convex length) / (fiber radius) within the above range is formed. It becomes difficult. A particularly preferable number of convex portions is 3 or 4, and a most preferable number of convex portions is four.

  Examples of the shape of the second component of the present embodiment are schematically shown in cross-sectional views in FIGS. In the conjugate fiber 10 shown in FIG. 1A, the second component 2 has a multi-leaf shape having four convex portions. In the conjugate fiber 10 shown in FIG. 1B, the second component 2 has a multi-leaf shape having three convex portions. In FIGS. 1A and 1B, reference numeral 1 denotes a first component.

  In the present embodiment, at least one of the convex portions has a maximum width from the convex portion base portion to the tip end, and (convex length) / (fiber radius) of 0.68 or more and 0.95 or less. Have Here, “the width of the convex portion”, “the length of the convex portion”, and “the fiber radius” are dimensions measured by the method described below.

[Convex length]
As shown in FIGS. 1 (a) and 1 (b), in the straight line connecting the center C of the multileaf core and the tip T of the convex portion, the intersection of the straight line and the line segment corresponding to the convex portion base B The distance L to the tip T of the convex portion is defined as the convex portion length. The tip T of the convex portion is a point that is farthest from the center of the multi-leaf shaped core portion on the outer periphery of the convex portion. The convex portion base B is a line segment that connects adjacent concave portions of the multileaf core.

[Width of convex part]
Of the line segments connecting any two points on the outer periphery of the convex portion, the length W of the line segment perpendicular to the straight line connecting the center C of the multileaf core and the tip T of the convex portion is the width of the convex portion. Equivalent to. Longest of the line segment corresponds to the maximum width W _M of the convex portion. Referred to as the minimum width W _S of the protrusion base portion of the shortest of the width measured between the maximum width W _M of the protrusion base B and the convex portion.

  The center of the multi-leaf shaped core is the same as the midpoint of the line segment connecting the convex bases in each convex part when the dimensions and shape of the convex parts are substantially the same and the cross-sectional shape is symmetrical in the vertical and horizontal directions. When a straight line connecting the tips of the convex portions is drawn, the straight lines intersect at a single point, so that the intersection is the center of the multi-leaf shaped core. In other cases, as shown in FIG. 2, when a straight line connecting the midpoint of the line segment corresponding to the convex portion base and the tip of the convex portion is drawn at each convex portion, the straight line is formed by the straight line. Among the triangles to be formed, the center of a circle inscribed in the triangle having the largest area is set as the center of the multi-leaf shaped core.

[Fiber radius]
When the outer circumference of the fiber is circular when the cross section of the fiber is observed with an electron microscope or the like, the radius of the circle is defined as the fiber radius. When the outer periphery of the fiber is not circular, the area of the cross section of the fiber is obtained, the radius of a perfect circle having the same area as the obtained area is calculated, and the radius is defined as the fiber radius. In particular, by slicing the fiber bundle with a cutter or the like to expose the cross section of the fiber, and observing this, when obtaining the fiber radius, the outer periphery of the fiber may be deformed by the force applied during slicing, In this case, the fiber radius is calculated from the area of the cross section.

When at least one convex portion has a shape having the maximum width (W _M ) from the convex portion base to the distal end, the thickness of the first component (fiber surface and convex (Corresponding to the shortest distance from the outer periphery). When a heat-bonded nonwoven fabric is produced using a composite fiber having a small thickness in the first component as a heat-bondable fiber, the heat-bonded portion formed on the nonwoven fabric is, for example, a core-sheath type in which the core is circular Compared with the case of using a composite fiber, it can be made smaller, and the touch of the nonwoven fabric becomes more flexible. Protrusions that have a W _M between the convex portions base to the tip, for example, (the shape of the portion excluding the handle) shaped like a bud, shaped like a mushroom, rice scoop shape, guttate, petaloid It may have a ginkgo leaf shape, a citrus tuft shape, a fan shape, or an oval shape.

  In the convex portion, the larger the (convex length) / (fiber radius), the smaller the area of the portion where the plurality of convex portions are connected, and it is easier to give a softer tactile feel when the nonwoven fabric is used. If the (projection length) / (fiber radius) is small, the multi-leaf shape increases the area of the portion where the plurality of projections are connected and approaches a circular shape. Thus, it is difficult for differences in the flexibility of the nonwoven fabric to occur. The convex portion whose (convex length) / (fiber radius) is within the above range may be one of the convex portions constituting the second component, may be plural, or all the convex portions. (Projection length) / (fiber radius) may be within the above range.

In this embodiment, in at least one of the convex portions constituting the second component, (distance in a direction parallel to the length of the convex portion from the convex portion base to the portion where the width of the convex portion is maximum) / (convex Part length) is preferably 0.6 or more and 0.9 or less, more preferably 0.6 or more and 0.85 or less, particularly preferably 0.61 or more and 0.80 or less, and most preferably 0. .62 or more and 0.78 or less. The distance in the direction parallel to the length of the convex part from the convex part base to the point where the width of the convex part is maximum (hereinafter also referred to as “B-W _M distance” for the sake of convenience) is longer, and therefore (B-W _M When the (distance) / (convex length) is larger, the position where the width of the convex portion becomes the maximum is closer to the outer periphery of the fiber. The convex part where the position where the width of the convex part becomes the maximum is closer to the fiber outer periphery has a shape protruding more toward the side closer to the fiber outer periphery, and when the convex part of such a shape is formed, the convex part The thickness of the first component becomes smaller near the tip of the part. Incidentally, _{B-W M} distance, in FIG. 1 (a), indicated by _{B-W M.} Protrusions (B-W _M distance) / (protrusion length) is within the above range may be one of the projections constituting the second component may be a plurality, or all of the About a convex part, (convex part length) / (fiber radius) may exist in said range.

  In this embodiment, in at least one of the convex portions, (maximum width of convex portion) / (minimum width of convex portion base) may be 2.0 or more and 3.3 or less, preferably 2.2 or more. It may be 3.2 or less, may be 2.4 or more and 3.2 or less, and may be 2.6 or more and 3.1 or less. (Maximum width of convex part) / (Minimum width of convex part base) indicates the degree of swelling of the convex part, and is too small, that is, (maximum width of convex part) / (minimum width of convex part base) is 1. When approaching, since the maximum width of the convex portion is too narrow, the shape of the convex portion is liable to collapse, or (the minimum width of the convex portion base) is too large, so that the area of the portion where the respective convex portion bases gather increases. When the shape of the convex portion collapses and adjacent convex portions come into contact with each other or are integrated, or the area of the portion where the convex portion bases gather increases, the shape of the second component approaches the same circle as a normal core-sheath-type conjugate fiber Therefore, the effect according to the present embodiment may not be obtained.

  On the other hand, if (maximum width of the convex portion) / (minimum width of the convex portion base) is too large, the maximum width of the convex portion is larger than necessary, or the minimum width of the convex portion base is extremely small, Adjacent convex portions are easily in contact with each other, or the shape of the second component is liable to collapse. When the convex portions come into contact with each other, or in some cases, or the shape of the second component collapses, the shape of the second component approaches the same circle as that of a normal core-sheath-type conjugate fiber, and thus the effect of this embodiment is achieved. It may not be obtained. The convex portion where (maximum width of convex portion) / (minimum width of convex portion base) is within the above range may be one of plural convex portions constituting the second component, or may be plural, or all of them. (Maximum width of the convex portion) / (minimum width of the convex portion base) may be within the above range.

  In the present embodiment, at least one of the convex portions, (maximum convex portion width) / (convex length) may be 0.7 or more and 0.95 or less, preferably 0.72 or more and 0.90 or less. It may be 0.75 or more and 0.88 or less, and may be 0.77 or more and 0.85 or less. (Maximum width of convex part) / (convex part length) can be said to be the aspect ratio of the convex part. If it is too small, the maximum width of the convex part is too small or the length of the convex part is too long. is there. If the maximum width of the convex portion is small, the shape of the second component approaches a circle, and thus the effect of the present embodiment may not be obtained. Further, if the convex part length is too long, an extremely thin part of the first component or a part where the second component is partially exposed to the fiber surface is generated. It may be reduced and fuzz is likely to occur, or the strength of the nonwoven fabric may be insufficient.

  On the other hand, when (maximum width of convex part) / (convex part length) is too large, the maximum width of the convex part is too large, or the convex part length is too short. If the maximum width of the convex portion is too large, adjacent convex portions are likely to contact each other, the shape of the second component collapses, and the cross-sectional shape of the second component becomes close to the same circle as a normal core-sheath conjugate fiber. The effect according to the present embodiment may not be obtained. Even when the length of the convex portion is too short, the cross-sectional shape of the second component is close to a circle, and the effect of this embodiment may not be obtained. The convex portion whose (maximum width of convex portion) / (convex portion length) is within the above range may be one of plural convex portions constituting the second component, or a plurality of convex portions, or all convex portions. (Maximum width of convex part) / (convex part length) may be within the above range.

In the above, as a parameter for specifying the shape of the convex portion,
a (convex length) / (fiber radius)
b _{(B-W M} distance) / (protrusion length)
c (maximum width of convex part) / (minimum width of convex part base)
d (maximum width of convex part) / (convex part length)
Cite. Of the convex portions constituting the second component, the convex portion satisfying a may satisfy one or more of b to d. For example, among the convex portions constituting the second component, one or a plurality of convex portions may satisfy a and b, may satisfy a and c, may satisfy a and d, or a And b and c may be satisfied, a, b, c and d may be satisfied, a, b and d may be satisfied, or a, c and d may be satisfied.

  One or more of the convex portions constituting the second component do not satisfy a, but may satisfy any one or more of b to d. For example, one or a plurality of convex portions may satisfy b and c, may satisfy b and d, may satisfy c and d, or may satisfy b, c, and d.

  In this embodiment, the minimum thickness of the first component (sheath portion) in the cross section (indicated by Dp in FIG. 1C), that is, the shortest distance between the second component and the fiber surface is 3 μm or less. Preferably, it is 2.5 μm or less, more preferably 2 μm or less, and particularly preferably 1.8 μm or less. The lower limit of the minimum thickness of the first component is, for example, 0.5 μm, and preferably 0.7 μm. When the fiber of the present embodiment is used as a heat-adhesive fiber, the heat-bonded part becomes point-bonded at the part where the thickness of the first component is small, and the texture of the nonwoven fabric becomes hard at the heat-bonded part. Can be suppressed. Therefore, according to the composite fiber in which the minimum thickness of the first component is 3 μm or less, a more flexible thermal bonding nonwoven fabric can be obtained. The minimum thickness of the first component is the shortest distance between each convex portion and the fiber surface when the cross-sectional shape of the second component is symmetrical vertically and horizontally, and the center coincides with the center of the fiber. Will be equal.

  In the present embodiment, the maximum thickness of the first component (sheath portion) may be, for example, 3 μm or more and 15 μm or less, and may be 5 μm or more and 12 μm or less. The maximum thickness of the first component is the length of the shortest line segment (hereinafter referred to as “recess depth” for convenience) of the line segments connecting the recess and the fiber outer periphery for each concave portion of the multi-leaf second component. 1 (b) and FIG. 1 (c), the maximum concave portion depth is obtained from the obtained concave depths. When the second component is symmetrical in the vertical and horizontal directions and the center thereof coincides with the center of the fiber, the concave depth is the same for all the concave portions, and the concave depths of all the concave portions are the maximum of the first component. It becomes thickness.

  In the present embodiment, the minimum thickness of the second component (core portion) may be, for example, not less than 0.5 μm and not more than 4.2 μm, and may be not less than 0.8 μm and not more than 4 μm. The minimum thickness of the second component is the length of the line segment connecting the concave portion where the largest concave portion depth (that is, the maximum thickness Dr of the first component (sheath portion)) is obtained and the center C of the second component. In FIG. 1 (b) and (c), it is indicated by Dc.

In the present embodiment, the second component can have a multileaf shape in which the distance between adjacent convex portions is relatively large. In particular, the second component of the conjugate fiber of the present embodiment has a relatively large (convex length) / (fiber radius) and a relatively long convex part, and (B-W _M distance) / (convex part length). The portion where the width of the convex portion is maximum can be made closer to the outer periphery of the fiber, that is, farther from the fiber center. Thereby, in the vicinity of the portion where the width of the convex portion is maximized, a sufficient distance is secured between the convex portions, and the distance between the convex portions can be increased.

  In the present embodiment, the composite ratio of the first component and the second component (first component / second component) may be 30 / 70-80 / 20, preferably 40 / 60-70 / 30 in volume ratio. More preferably, it is 50/50 to 65/35. It is difficult to obtain a core-sheath type composite fiber having a core part having the above shape and size ratio with a composite ratio outside this range. Moreover, when the fiber of which the ratio of a 1st component is too small is used as a heat bondable fiber, heat bond strength may become inadequate. When the ratio of the second component is too small, the strength of the fiber is lowered, and the mechanical strength of the nonwoven fabric may be insufficient.

  The fineness of the composite fiber of the present embodiment is not particularly limited, and may be, for example, 0.6 dtex or more and 15 dtex or less, preferably 0.8 dtex or more and 10 dtex or less, more preferably 1.0 dtex or more and 8 dtex or less. is there. The composite fiber according to the present embodiment is a core-sheath type composite having a core portion with a fineness of 1.6 dtex or more and 2.8 dtex or less having a circular shape and no convex portion even when the fineness is set to 2.0 dtex or more and 2.8 dtex or less. A non-woven fabric that is as soft as or more flexible than the fibers can be obtained.

  The fiber length of the composite fiber of this embodiment is not particularly limited. When producing a nonwoven web using a card machine, the fiber may be in the form of a finite length of short fiber, the fiber length may be in the range of 1 mm to 100 mm, for example, Preferably it exists in the range of 28 mm-72 mm, More preferably, it is 32 mm-64 mm. In the case of producing a fiber web using an airlaid machine, the fiber length may be in the range of 3 mm to 30 mm, and preferably in the range of 5 mm to 25 mm. When producing a fiber web by the wet papermaking method, the fiber length may be in the range of 1.5 mm to 20 mm, preferably in the range of 1 mm to 10 mm.

(Second embodiment (core-sheath type composite fiber))
As described above, the conjugate fiber of the first embodiment has a small area of the portion where the convex bases gather in the second component. When the core-sheath composite fiber is manufactured by selecting the spinning nozzle and the spinning conditions so that the second component can be realized, one or two when the fiber cross section is observed due to fluctuations in the manufacturing conditions. The plurality of protrusions may be “disconnected” or “broken” or appear to be so. Further, the fibers in which the convex portions are “separated” or “broken” may be included in a certain ratio in one lot when the fibers of the first embodiment are manufactured. Such a fiber in which a part of the convex portion is “separated” or “teared” gives a soft tactile nonwoven fabric as in the fiber of the first embodiment, and is included in the embodiment of the present invention. Is. Therefore, such a fiber will be described below as a second embodiment.

The core-sheath composite fiber of the second embodiment includes a first component made of a thermoplastic resin and a second component made of a thermoplastic resin having a higher melting point after spinning than the melting point of the first component after spinning. The first component constitutes a sheath that occupies the entire fiber surface, and the second component has two or more convex portions in the cross-sectional shape. A leaf-shaped core portion and one or a plurality of droplet-shaped, petal-shaped, ginkgo leaf-shaped, citrus tufted, fan-shaped, or elliptical deformed core portions are configured, and at least one of the deformed core portions is It has the maximum width from the base (in the deformed core, the tip near the center of the fiber, the same applies hereinafter) to the tip, and is 0.68 or more and 0.95 or less (length of the deformed core ) / (Fiber radius).
Since the first component and the second component are as described in the first embodiment, the description thereof is omitted here.

  In the present embodiment, the second component is a multi-leaf-shaped core having two or more convex portions in cross-sectional shape, and one or more drops, petals, ginkgo leaves, citrus tufts, It forms a fan-shaped or elliptical deformed core. In other words, the second component has a configuration in which one or a plurality of convex portions are separated or broken from a multi-leaf shape having three or more convex portions.

  The example of the shape of the 2nd component of this embodiment is shown with sectional drawing in Fig.3 (a)-(c). In these drawings, reference numeral 12a is a deformed core, and reference numeral 12b is a multi-leaf shaped core. In the fiber 20 shown in FIG. 3 (a), the second component is composed of one irregularly shaped core portion 12a and a multi-leaf shaped core portion 12b having three convex portions, and four convex portions. It seems that one convex part has come off from the multi-leaf shape which has. In the fiber 20 shown in FIG. 3 (b), the second component is composed of two irregularly shaped core parts 12a and a multi-leaf shaped core part 12b having two convex parts, and four convex parts. It looks as if the two convex parts were removed from the multi-leaf shape having the. In the fiber 20 shown in FIG.3 (c), the 2nd component is comprised by one irregular core part 12a and the multi-leaf shaped core part 12b which has two convex parts, and three convex parts It seems that one convex part has come off from the multi-leaf shape which has.

  In the present embodiment, at least one of the deformed core portions has a maximum width from the base portion to the tip end, and (deformed core portion length) / (fiber radius) of 0.68 or more and 0.95 or less. Have. Here, “length of deformed core part” and “width of deformed core part” are dimensions measured by the method described below. The method for measuring the “fiber radius” is as described above with respect to the first embodiment.

[Different core length]
The length of the line segment connecting the base B ′ of the deformed core and the tip T ′ of the deformed core is defined as the deformed core length L ′. The base B ′ of the deformed core is an end on the side close to the center of the fiber, and is usually the thinnest part or in the vicinity thereof. The tip T ′ of the deformed core portion is a point farthest from the base B ′ of the deformed core portion. FIG. 4 shows the base B ′ and the tip T ′ of the drop-shaped deformed core.

[Width of irregular core]
Of the line segments connecting any two points on the outer periphery of the deformed core portion, the length of the line segment orthogonal to the direction parallel to the deformed core portion length L ′ corresponds to the width of the deformed core portion. The longest of these line segments corresponds to the maximum width W _M ′ of the deformed core part. In the present embodiment, the deformed core portion has the maximum width W _M ′ from the base portion to the tip end.

  When at least one deformed core portion has a shape having the maximum width from the base portion to the tip end, the thickness of the first component (the fiber surface and the outer periphery of the convex portion) at the tip end portion of the deformed core portion. Equivalent to the shortest distance). Further, in the present embodiment, there is a deformed core portion in which (deformed core length) / (fiber radius) is within the above range, together with a multileaf core portion having two or more convex portions. These core portions can be considered to be formed by “disengaging” or “splitting” the convex portions of the second component described in the first embodiment. Therefore, the conjugate fiber of this embodiment can exhibit the same effect as the conjugate fiber of the first embodiment.

In the present embodiment, in at least one deformed core part constituting the second component, (distance in the direction parallel to the deformed core part length from the base of the deformed core part to the maximum width) / (deformed core part length) Is preferably 0.6 or more and 0.9 or less. Effect of deformed core satisfies such dimensional ratio is the composite fiber of the first embodiment, (B-W _M distance) / (protrusion length) of 0.6 to 0.9 It is the same as the effect brought about by being.

  In the present embodiment, in at least one of the deformed core portions, (maximum width of the deformed core portion) / (length of the deformed core portion) may be 0.7 or more and 0.95 or less, preferably 0. It may be 72 or more and 0.90 or less, may be 0.75 or more and 0.88 or less, and may be 0.77 or more and 0.85 or less. In the deformed core part, the effect of (maximum width of deformed core part) / (length of deformed core part) within this range is as described above in relation to the first embodiment.

In the above, as a parameter for specifying the shape of the deformed core part,
a ′ (length of irregular core) / (fiber radius)
b '(distance in the direction parallel to the length of the deformed core from the base of the deformed core to the maximum width) / (length of the deformed core)
c '(maximum width of deformed core) / (length of deformed core)
Cite. Of the irregularly shaped core portions, the convex portion satisfying a ′ may satisfy one or both of b ′ and c ′. For example, one or more of the deformed core portions may satisfy a ′ and b ′, may satisfy a ′ and c ′, or may satisfy a ′, b ′, and c ′. Good. Further, one or more of the deformed core portions do not satisfy a ′, but may satisfy one or both of b ′ and c ′.

  In the present embodiment, the minimum thickness of the first component (sheath portion) in the cross section, that is, the shortest distance between the second component and the fiber surface may be 3 μm or less, preferably 2.5 μm or less. More preferably 2 μm or less, particularly preferably 1.8 μm or less. The lower limit of the minimum thickness of the first component is, for example, 0.5 μm, and preferably 0.7 μm. The effect of the minimum minimum thickness of the first component is as described above in relation to the first embodiment.

  Other configurations (composite ratio, fineness, fiber length, etc.) of this embodiment are as described in relation to the first embodiment. Therefore, the description thereof is omitted here.

(Manufacturing method of composite fiber)
The core-sheath type composite fiber of the first embodiment and / or the second embodiment (hereinafter collectively referred to as “multi-leaf core-sheath type composite fiber”) is produced, for example, as follows. Can do. First, a thermoplastic resin that forms each of the first component and the second component is prepared. Subsequently, in order to obtain a desired fiber cross-sectional structure, composite spinning is performed using an appropriate composite type nozzle, and the fiber is drawn at a take-up speed of 100 to 1500 m / min to obtain a spun filament. The fineness of the spinning filament may be 1.5 dtex or more and 60 dtex or less. As described above, even when trying to obtain the fibers of the first embodiment during composite spinning, the fibers of the second embodiment may be inevitably included, and vice versa.

  The spun filament is then drawn as needed. The spinning filament may be stretched at a magnification of 1.5 times or more and 8 times or less at a stretching temperature of 50 ° C. or higher and 160 ° C. or lower depending on the type of thermoplastic resin constituting the fiber. The stretching method is not particularly limited, and wet stretching is performed while heating with a high-temperature liquid such as warm water (50 ° C. or more and less than 100 ° C.), and dry stretching is performed while heating in a high-temperature gas or a high-temperature metal roll. A known stretching method such as steam stretching in which steam is stretched while heating the fiber under normal pressure or a pressurized state of water vapor at 100 ° C. or higher may be used.

  A predetermined amount of fiber treatment agent is adhered to the obtained drawn filament as necessary, and mechanical crimping is given by a crimper (crimping device). The number of crimps may be, for example, 5 pieces / 25 mm to 25 pieces / 25 mm, preferably 8 pieces / 25 mm to 20 pieces / 25 mm, and more preferably 10 pieces / 25 mm to 18 pieces / 25 mm. Thereafter, it is cut into a predetermined fiber length.

(raw cotton)
Synthetic fibers are manufactured and sold in a certain amount as raw cotton or raw fiber for the production of nonwoven fabrics and the like. As described above, when trying to manufacture the conjugate fiber of the first embodiment, the conjugate fiber of the second embodiment may be inevitably included, or vice versa. Therefore, in the product provided as raw cotton, both the fibers of the first embodiment and the fibers of the second embodiment may be included. According to such raw cotton, a flexible and smooth non-woven fabric can be obtained. In the raw cotton, the proportion of the fibers of the second embodiment is not particularly limited, and may be, for example, 3% by mass to 80% by mass, 3% by mass to 75% by mass, and 3% by mass to 70% by mass. The mass% or less may be sufficient.

(Nonwoven fabric)
Another embodiment of the present invention is a nonwoven fabric comprising the fibers of the first embodiment and / or the fibers of the second embodiment. In the nonwoven fabric of this embodiment, the fibers may be thermally bonded by the first component. The nonwoven fabric may contain only 20% by mass or more of the fibers of the first embodiment, or may contain only 20% by mass or more of the fibers of the second embodiment, or both together 20% by mass. These may be included.

  The non-woven fabric may contain 50% by mass or more of the fiber of the first embodiment, and may be composed of only the fiber of the first embodiment, for example. Or a nonwoven fabric may contain the fiber of 2nd Embodiment 50 mass% or more, for example, may be comprised only with the fiber of 2nd Embodiment. Or a nonwoven fabric may contain 50 mass% or more of the fiber of both forms together, for example, may be comprised only with the fiber of both forms. When the nonwoven fabric includes fibers of both forms, the fibers of the second embodiment occupy 3% by mass or more and 80% by mass or less when the total amount of the fibers of both forms is 100% by mass. Good.

  The non-woven fabric may contain fibers other than the multi-leaf core-sheath composite fiber. Other fibers include, for example, natural fibers such as cotton, silk, wool, hemp, and pulp, recycled fibers such as rayon, cupra, and solvent-spun cellulose fibers, and acrylic, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene Polyesters such as terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and copolymers thereof, amides such as nylon 6, nylon 12 and nylon 66, polypropylene, polyethylene (high density polyethylene, low density polyethylene, etc. ), Polyolefins such as polybutene-1, ethylene-vinyl alcohol copolymer, and ethylene-vinyl acetate copolymer, and synthetic fibers such as polyurethane. The synthetic fiber may be a single fiber or a composite fiber. For example, the composite fiber may be a core-sheath type composite fiber or a split type composite fiber. Further, as other fibers, two or more fibers may be used in combination.

  As described above, the nonwoven fabric may be one in which fibers are integrated by thermal bonding. Alternatively, the nonwoven fabric may be one in which fibers are entangled and integrated by needle punch processing or fluid flow entanglement processing. Alternatively, the nonwoven fabric may have been subjected to a thermal bonding process after the entanglement process. As described above, according to the multi-leaf-core-sheath type composite fiber, at least a part of the heat-bonding portion is formed at a small thickness of the first component and has a smaller area or volume. Therefore, when the nonwoven fabric of this embodiment is a thermobonding nonwoven fabric, thermal bonding is not likely to be strong, and the nonwoven fabric has a soft touch as a whole.

When the non-woven fabric of this embodiment is provided as a thermobonding non-woven fabric, the thermobonding non-woven fabric is produced by using a multi-leaf core-sheath type composite fiber and, if necessary, a fiber web, and heat-treating the fiber web. Thus, the first component of the multi-leaf core-sheath composite fiber may be manufactured by a method in which the fibers are thermally bonded.
The form of the fiber web may be any one selected from a card web such as a parallel web, a cross web, a semi-random web and a random web, an air lay web, a wet papermaking web, and a spunbond web. It is appropriately selected depending on. For example, a card web is advantageous in terms of the cost of manufacturing the nonwoven fabric and provides a heat-bonded nonwoven fabric with a soft feel that is particularly suitable for the topsheet of absorbent articles.

  Next, the fiber web is heat-treated, and the fibers are thermally bonded with the first component of the multi-leaf core-sheath composite fiber. The heat treatment may be a hot air processing treatment in which hot air is applied to the fiber web, a heat treatment using infrared rays, or a method using a hot roll. The hot air processing may be performed using, for example, an air-through processing machine (hot air penetration type heat treatment machine) and a hot air blowing type heat treatment machine.

  The heat treatment temperature and the heat treatment time are selected according to the heat treatment method so that the resin constituting the first component is softened or melted and becomes sufficient to join the fibers. For example, when the first component is high-density polyethylene and heat bonding is performed by hot air processing, the heat treatment temperature is preferably 130 ° C. or more and less than 165 ° C., and the heat treatment time is 0.2 seconds or more and 25 seconds or less. It is. When the first component is low density polyethylene or linear low density polyethylene and heat bonding is performed by hot air processing, the heat treatment temperature is preferably 120 ° C. or more and less than 145 ° C., and the heat treatment time is 0. .2 seconds or more and 25 seconds or less.

  If desired, the fiber web may be subjected to a fiber entanglement treatment prior to heat treatment. When the fiber entanglement treatment is performed, a dense nonwoven fabric is obtained. The fiber entanglement process may be, for example, a needle punch process or a fluid flow (particularly water flow) entanglement process.

The basis weight of the nonwoven fabric is not particularly limited, and is appropriately selected according to the use. Basis weight of the nonwoven fabric may be, for example, ^{5g / m 2 ~120g / m 2} , may be ^{10g / m 2 ~100g / m 2} . More specifically, the nonwoven fabric, when used as a topsheet of an absorbent article, the basis weight may be a ^{12g / m 2 ~ 90g / m} 2, may be ^{15g / m 2 ~80g / m 2} . The thickness of the nonwoven fabric is not particularly limited, for example, in the case of non-woven fabric having a basis weight of ^{5g / m 2 ~120g / m 2} , the thickness may be from 0.2 mm and 5 mm.

  The nonwoven fabric of this embodiment can be used for various applications, and is preferably used for a product for skin contact that is used by directly applying to the skin, taking advantage of its flexibility and smooth touch, in which case the nonwoven fabric of this embodiment is Occupies at least part of the surface that contacts the skin. Skin contact products include, for example, sanitary articles such as masks, supporters and bandages, absorbent articles such as disposable diapers, sanitary napkins, and sheets for cages, and liquid-impregnated skin-coated sheets impregnated with liquids such as cosmetics ( For example, a face mask, a keratin care sheet, a decollete sheet, etc.).

  The nonwoven fabric of this embodiment is particularly preferably used as a surface sheet for absorbent articles. As described above, even if the multi-leaf core-sheath type composite fiber is increased in its fineness, it can provide a flexible nonwoven fabric and can reduce the area of the thermal bonding portion. Therefore, in order to improve liquid permeability, for example, even if a non-woven fabric is formed using a multileaf core-sheath type composite fiber having a fineness of 2.0 dtex or more and 2.8 dtex or less, the fineness is 1.6 dtex or more and 2.6 dtex or less. The same flexibility and tactile sensation as those obtained using a normal core-sheath type composite fiber (one having a circular core shape) can be obtained.

Example 1
The first component consists of high density polyethylene (melting point before spinning: 128 ° C.), the second component consists of polyethylene terephthalate (melting point before spinning: 253 ° C.), and the two components are 60/40 (first / second). Core-sheath type composite fibers arranged so as to have a cross-sectional shape shown in FIG. Specifically, the spinning temperature of the first component was 270 ° C., the spinning temperature of the second component was 330 ° C., the take-up speed was 1400 m / min, and a spun filament with a fineness of 3.6 dtex was obtained. Subsequently, the spun filament was stretched 2.3 times in warm water at 80 ° C. to obtain a stretched filament having a fineness of 2.1 dtex. Next, after applying the fiber treating agent, 15 crimps / 25 mm of mechanical crimps were applied to the drawn filaments using a stuffing box type crimper. Thereafter, a drying treatment was performed, and a composite fiber was obtained by cutting into a fiber length of 51 mm.

(Example 2)
The first component consists of high density polyethylene (melting point before spinning: 128 ° C.), the second component consists of polyethylene terephthalate (melting point before spinning: 253 ° C.), and the two components are 60/40 (first / second). Core-sheath type composite fibers arranged so as to have a cross-sectional shape shown in FIG. Specifically, the spinning temperature of the first component was 270 ° C., the spinning temperature of the second component was 330 ° C., the take-up speed was 1400 m / min, and a spun filament with a fineness of 5.6 dtex was obtained. Next, the spun filament was drawn 2.7 times in warm water at 80 ° C. to obtain a drawn filament having a fineness of 2.6 dtex. Next, after applying the fiber treating agent, 15 crimps / 25 mm of mechanical crimps were applied to the drawn filaments using a stuffing box type crimper. Thereafter, a drying treatment was performed, and a composite fiber was obtained by cutting into a fiber length of 51 mm.

(Comparative Example 1)
The first component consists of high-density polyethylene (melting point before spinning: 128 ° C.), the second component consists of polyethylene terephthalate (melting point before spinning: 253 ° C.), and the composite ratio of the two components is 60/40 (first / first). 2), and a core-sheath type composite fiber having a circular second component was produced. Specifically, the spinning temperature of the first component was 270 ° C., the spinning temperature of the second component was 330 ° C., the take-up speed was 1400 m / min, and a spun filament with a fineness of 5.6 dtex was obtained. Next, the spun filament was drawn 2.7 times in warm water at 80 ° C. to obtain a drawn filament having a fineness of 2.6 dtex. Next, after applying the fiber treating agent, 15 crimps / 25 mm of mechanical crimps were applied to the drawn filaments using a stuffing box type crimper. Thereafter, a drying treatment was performed, and a composite fiber was obtained by cutting into a fiber length of 51 mm.

(Comparative Example 2)
The first component consists of high-density polyethylene (melting point before spinning: 128 ° C.), the second component consists of polyethylene terephthalate (melting point before spinning: 253 ° C.), and the composite ratio of the two components is 60/40 (first / first). 2), and a core-sheath type composite fiber having a circular second component was produced. Specifically, the spinning temperature of the first component was 270 ° C., the spinning temperature of the second component was 330 ° C., the take-up speed was 1500 m / min, and a spun filament with a fineness of 3.6 dtex was obtained. Next, the spun filament was stretched 2.3 times in warm water at 80 ° C. to obtain a stretched filament having a fineness of 2.2 dtex. Next, after applying the fiber treating agent, 15 crimps / 25 mm of mechanical crimps were applied to the drawn filaments using a stuffing box type crimper. Thereafter, a drying treatment was performed, and a composite fiber was obtained by cutting into a fiber length of 51 mm.

(Comparative Example 3)
The first component consists of high-density polyethylene (melting point before spinning: 128 ° C.), the second component consists of polyethylene terephthalate (melting point before spinning: 253 ° C.), and the composite ratio of the two components is 60/40 (first / first). 2), and a core-sheath type composite fiber having a circular second component was produced. Specifically, the spinning temperature of the first component was 270 ° C., the spinning temperature of the second component was 330 ° C., the take-up speed was 1500 m / min, and a spinning filament having a fineness of 3.5 dtex was obtained. Subsequently, the spun filament was stretched 2.4 times in warm water at 80 ° C. to obtain a stretched filament having a fineness of 1.8 dtex. Next, after applying the fiber treating agent, 15 crimps / 25 mm of mechanical crimps were applied to the drawn filaments using a stuffing box type crimper. Thereafter, a drying treatment was performed, and a composite fiber was obtained by cutting into a fiber length of 38 mm.

(Comparative Example 4)
The first component 51 is made of high-density polyethylene (melting point before spinning: 128 ° C.), the second component 52 is made of polyethylene terephthalate (melting point before spinning: 253 ° C.), and the two components are 60/40 (first / second). The core-sheath type composite fiber 50 arranged to have the cross-sectional shape shown in FIG. Specifically, the spinning temperature of the first component was 270 ° C., the spinning temperature of the second component was 330 ° C., the take-up speed was 1500 m / min, and a spun filament with a fineness of 3.6 dtex was obtained. Next, the spun filament was stretched 2.3 times in warm water at 80 ° C. to obtain a stretched filament having a fineness of 2.2 dtex. Next, after applying the fiber treating agent, 15 crimps / 25 mm of mechanical crimps were applied to the drawn filaments using a stuffing box type crimper. Thereafter, a drying treatment was performed, and a composite fiber was obtained by cutting into a fiber length of 51 mm.
A synthetic fiber was obtained.

Nonwoven fabrics were produced from the conjugate fibers obtained in each of the Examples and Comparative Examples, and the mechanical properties of the nonwoven fabrics were evaluated, and the flexibility and smoothness of the nonwoven fabrics were evaluated by a sensory test. The nonwoven fabric is produced by producing a fiber web having a basis weight of about 30 g / m ² with a roller card machine, and subjecting the obtained fiber web to a heat treatment for 12 seconds with an air-through processing machine (hot air penetration type heat treatment machine) set at 140 ° C. Then, the fiber was obtained by a method of thermally bonding the fibers together. The mechanical properties of the nonwoven fabric were evaluated by the methods shown below.

(thickness)
Using a thickness measuring machine (trade name: THICKNESS GAUGE model CR-60A, manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), measurement was performed with a load of 2.94 cN per 1 cm ^{2 of} the sample.

(MD strength, MD elongation, 10% MD strength)
According to JIS L 1096 6.12.1 A method (strip method), using a constant speed tension type tensile tester, under conditions of a specimen width of 5 cm, a grip interval of 10 cm, and a tensile speed of 30 ± 2 cm / min. A tensile test was performed, and a load value (tensile strength) at break, elongation at break, and stress at 10% elongation were measured. The tensile test was carried out with the longitudinal direction (MD direction) of the nonwoven fabric as the tensile direction. All the evaluation results are shown as an average of values measured for three samples.

(Sensory test)
Each of the five monitors touched all samples and ranked for flexibility and smoothness. The 1st place was 3 points, 2nd place was 5 points, 3rd place was 10 points, 4th place was 12 points, 5th place was 15 points, and 6th place was 20 points. The smaller the total score, the more monitors are judged to be more flexible or smoother. The evaluation was as follows according to the total score.
++: Total score 15 to 45 points +: Total score 46 to 65 points-: Total score 66 to 100 points

  Table 1 shows the structure of the fibers, the cross-sectional shape of the fibers, the mechanical properties of the nonwoven fabric, and the results of the sensory test of the nonwoven fabric obtained in each Example and Comparative Example. Each dimension related to the cross-sectional shape of the fiber was observed by enlarging the fiber cross section with a scanning electron microscope 1000 times with respect to the obtained fibers of Examples 1 and 2 and Comparative Examples 1 to 4, and 20 fibers Was extracted at random, and the extracted fibers were measured by the method described in the first embodiment, and the average value was obtained. Since the cross-sectional shape of the second component of the fibers of Comparative Examples 1 to 3 was circular, the dimensions related to the convex portions could not be measured. In the fiber of Comparative Example 4, the width of the convex portion of the second component was almost constant throughout, so the width of the convex portion was set as the maximum width of the convex portion, and the minimum width of the convex portion base was not obtained.

  Although the fiber of Example 1 has a fineness greater than that of Comparative Example 3, the same evaluation was obtained in the sensory test of the nonwoven fabric. From this, the cross-sectional shape of the second component is the flexibility and smoothness of the nonwoven fabric. It can be seen that it contributes to Moreover, the nonwoven fabric produced with the fibers of Example 1 was clearly superior in terms of flexibility and smoothness to the nonwoven fabric produced with the fibers of Comparative Example 2 having substantially the same fineness. Similarly, the nonwoven fabric produced with the fibers of Example 2 was superior in flexibility and smoothness to the nonwoven fabric produced with the fibers of Comparative Example 1 having the same fineness. Although the fiber of the comparative example 4 is a multileaf shape in which the second component has four convex portions, the convex portion length is short, the convex portion width is constant over the entire convex portion, and the shape is close to a circle. The flexibility and smoothness of the nonwoven fabric were the same as those of Comparative Example 2.

The nonwoven fabric of this embodiment includes the following aspects.
(Aspect 1)
A first component composed of a thermoplastic resin, and a second component composed of a thermoplastic resin having a melting point after spinning higher than the melting point after spinning of the first component,
In a cross section cut along a plane perpendicular to the length direction, the first component constitutes a sheath that occupies the entire fiber surface, and the second component has a plurality of convex portions in the cross-sectional shape. Configure the leaf-shaped core,
At least one of the convex portions has a maximum width from the convex portion base to the tip, and has a (convex length) / (fiber radius) of 0.68 or more and 0.95 or less.
Core-sheath type composite fiber.
(Aspect 2)
In at least one of the convex portions, (distance in a direction parallel to the convex portion length from the base portion of the convex portion to the maximum convex portion width) / (convex length) is 0.6 or more and 0.9 or less. The core-sheath type composite fiber according to aspect 1, wherein
(Aspect 3)
The core-sheath type composite fiber according to aspect 1 or 2, wherein the shortest distance between the second component and the fiber surface is 3 μm or less in the cross section.
(Aspect 4)
In at least one of the convex portions, the core-sheath type composite fiber according to any one of aspects 1 to 3, wherein (maximum width of the convex portion) / (minimum width of the convex portion base) is 2.0 or more and 3.2 or less. .
(Aspect 5)
In at least one of the convex portions, the core-sheath type composite fiber according to any one of aspects 1 to 4, wherein (maximum convex portion width) / (convex length) is 0.7 or more and 0.95 or less.
(Aspect 6)
The core-sheath type composite fiber according to any one of aspects 1 to 5, wherein the number of convex portions is 3 or more and 6 or less.
(Aspect 7)
A first component composed of a thermoplastic resin, and a second component composed of a thermoplastic resin having a melting point after spinning higher than the melting point after spinning of the first component,
In a cross section cut along a plane perpendicular to the length direction, the first component constitutes a sheath that occupies the entire fiber surface, and the second component has a plurality of convex portions in the cross-sectional shape. A leaf-shaped core and one or more drops, petals, ginkgo leaves, citrus tufts, fan-shaped or elliptical deformed cores,
At least one of the deformed core portions has a maximum width from the base to the tip of the deformed core portion, and (deformed core length) / (fiber radius) of 0.68 or more and 0.95 or less. Have
Core-sheath type composite fiber.
(Aspect 8)
In at least one of the deformed core portions, (distance in a direction parallel to the length of the deformed core portion from the base of the deformed core portion to the maximum width) / (length of the deformed core portion) is 0.6 or more and 0.9. The core-sheath-type composite fiber of aspect 7 which is the following.
(Aspect 9)
The core-sheath type composite fiber according to aspect 7 or 8, wherein the shortest distance between the first component and the fiber surface in the cross section is 3 μm or less.
(Aspect 10)
The core-sheath type composite according to any one of aspects 7 to 9, wherein in at least one of the deformed core portions, (maximum width of deformed core portion) / (length of deformed core portion) is 0.7 or more and 0.95 or less. fiber.
(Aspect 11)
A raw cotton comprising any one of the sheath-core conjugate fibers according to any one of aspects 1 to 6 and any one of the sheath-core conjugate fibers according to any one of aspects 7 to 10.
(Aspect 12)
A nonwoven fabric comprising 20% by mass or more of any one of the core-sheath composite fibers according to any one of aspects 1 to 10, wherein the fibers are thermally bonded to each other by the first component.
(Aspect 13)
A sheet for absorbent articles, comprising the nonwoven fabric of aspect 12.

  The composite fiber of the present invention in which the second component has a specific shape can give a nonwoven fabric having a smooth tactile sensation and flexibility, such as a surface sheet of an absorbent article, a product that comes into contact with the skin, and the like. Suitable for configuring.

DESCRIPTION OF SYMBOLS 10 Composite fiber 1 1st component 2 2nd component 12a Atypical core part 12b Multilobe-shaped core part 20 Composite fiber 50 Composite fiber 51 1st component 52 2nd component

Claims (11)

A first component composed of a thermoplastic resin, and a second component composed of a thermoplastic resin having a melting point after spinning higher than the melting point after spinning of the first component,
In a cross section cut along a plane perpendicular to the length direction, the first component constitutes a sheath that occupies the entire fiber surface, and the second component has a plurality of convex portions in the cross-sectional shape. Configure the leaf-shaped core,
In at least one of the convex portions, (distance in a direction parallel to the convex portion length from the base portion of the convex portion to the place where the width of the convex portion is maximum) / (convex length) is 0.6 or more and 0.9 or less. Is,
Core-sheath type composite fiber.   The core-sheath-type conjugate fiber according to claim 1, wherein the shortest distance between the second component and the fiber surface in a cross section is 3 µm or less.   The core-sheath-type conjugate fiber according to claim 1 or 2, wherein at least one of the convex portions has (maximum convex portion width) / (minimum convex portion base width) of 2.0 or more and 3.2 or less.   The core-sheath type composite according to any one of claims 1 to 3, wherein at least one of the protrusions has (maximum width of the protrusion) / (length of the protrusion) of 0.7 to 0.95. fiber.   The number of convex parts is 3 or more and 6 or less, The core-sheath-type composite fiber of any one of Claims 1-4. A first component composed of a thermoplastic resin, and a second component composed of a thermoplastic resin having a melting point after spinning higher than the melting point after spinning of the first component,
In a cross section cut along a plane perpendicular to the length direction, the first component constitutes a sheath that occupies the entire fiber surface, and the second component has a plurality of convex portions in the cross-sectional shape. A leaf-shaped core and one or more drops, petals, ginkgo leaves, citrus tufts, fan-shaped or elliptical deformed cores,
In at least one of the deformed core portions, (distance in a direction parallel to the length of the deformed core portion from the base of the deformed core portion to the maximum width) / (length of the deformed core portion) is 0.6 or more and 0.9. Is
Core-sheath type composite fiber.   The core-sheath-type conjugate fiber according to claim 6, wherein the shortest distance between the second component and the fiber surface in a cross section is 3 µm or less.   The core-sheath type composite fiber according to claim 6 or 7, wherein in at least one of the irregular core parts, (maximum width of the irregular core part) / (length of the irregular core part) is 0.7 or more and 0.95 or less. .   A raw cotton comprising the core-sheath type composite fiber according to any one of claims 1 to 5 and the core-sheath type composite fiber according to any one of claims 6 to 8.   A nonwoven fabric comprising 20% by mass or more of the core-sheath composite fiber according to any one of claims 1 to 8, wherein the fibers are thermally bonded to each other by the first component.   The sheet | seat for absorbent articles which comprises the nonwoven fabric of Claim 10.

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