JPH11200151A - Thermally splittable composite fiber and heat-fused ultrafine fiber nonwoven fabric using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-fusible ultrafine fiber excellent in texture (flexibility and tactile sensation) using the heat-dividing conjugate fiber because the cardability of the conventional heat-dividing conjugate fiber is not so good. It is difficult to obtain a nonwoven fabric at a high yield. SOLUTION: In obtaining the heat-dividing conjugate fiber, when a cross section in the radial direction of the heat-dividing conjugate fiber is taken, a pool formed at the center of the fiber and a radially extending from the pool toward the fiber surface. These components are formed such that a main segment having a shape having a plurality of extended branches is formed of a polypropylene resin, and a plurality of sub-segments separated by the pool and the branches are formed of polyethylene terephthalate. In addition, the sub-segment, which reaches the fiber surface from the pool portion among the boundary lines with the main segment, has an average degree of curvature of 5 to 13 on the main segment side.
It is formed to indent below the%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a splittable conjugate fiber and a microfiber nonwoven fabric using the same, and more particularly to a splittable conjugate fiber which is split by mechanical impact and thermal treatment (hereinafter referred to as "heat splittable conjugate fiber"). And a heat-fused ultrafine fiber nonwoven fabric using the same.

[0002]

2. Description of the Related Art Ultrafine fibrous nonwoven fabrics have a softer touch than ordinary nonwoven fabrics, and their demand is increasing as a surface material for disposable products used for direct contact with the human body, such as disposable diapers and sanitary products. This ultrafine fiber non-woven fabric is generally manufactured using splittable conjugate fibers as material fibers. The split conjugate fibers are mainly split by physical treatment (mechanical impact), and are subjected to mechanical impact and thermal treatment. Can be roughly divided into fibers (thermo-spliable conjugate fibers).

[0003] The heat-dividing conjugate fiber can be split by a heat-sealing facility owned by most nonwoven fabric manufacturers, and can be made into a nonwoven fabric. Therefore, by using a heat-division conjugate fiber as the splittable conjugate fiber, it is possible in many cases to produce a heat-fused ultrafine fiber nonwoven fabric without investing in new equipment.
For this reason, the production of a heat-fused ultrafine fiber nonwoven fabric using the heat-dividing conjugate fiber as a material fiber is rapidly spreading.

[0004] As a heat-division conjugate fiber having the above-mentioned advantages, a specific fiber-forming polymer component B, ie, a specific fiber-forming polymer component B on the outer periphery of a polyolefin component A (for example, a polypropylene resin) when a cross section in the fiber diameter direction is taken, A fiber-forming polymer component B having a melting point difference of 20 ° C. or more from the polyolefin component A and exhibiting incompatibility with the polyolefin component A;
(For example, polyethylene terephthalate)
When the polyolefin component A and the fiber-forming polymer component B have a shape in which the convex portions have a shape provided at intervals or have a cross section in the fiber radial direction, the polyolefin component A and the fiber-forming polymer component B are arranged in the circumferential direction. It has been known to have a multi-layered hollow fiber shape which is alternately distributed along the periphery (all disclosed in Japanese Patent Application Laid-Open No. 2-16 / 1990).
No. 9720).

Japanese Patent Application Laid-Open No. Hei 6-73613 discloses that
A first component composed of a fiber-forming thermoplastic resin (eg, polyethylene terephthalate) having a melting point higher than 130 ° C. and lower than 350 ° C. and a specific thermoplastic resin (eg, a polypropylene-based resin) having a melting point lower than the first component by 20 ° C. or more. (A) and (b) below, which are formed by the second component.

(A) When the cross section in the fiber radial direction is taken, these components are distributed so that the first component is divided into two or more by the second component, and the second component is compounded by heat treatment. A thermally splittable conjugate fiber that separates from fibers into two or more ultrafine fibers, and also splits the first component into two or more ultrafine fibers.

(B) When the cross section in the fiber radial direction is taken, the first component is divided into two or more by the second component, and the first component forms a pool at the center of the fiber. These components are distributed as described above, and the second component is separated from the conjugate fiber by heat treatment to form two or more ultrafine fibers, and the first component becomes one ultrafine fiber without being split, and is a heat-dividable conjugate fiber. .

[0008]

The heat-fusible ultrafine fiber nonwoven fabric using the heat-dividing conjugate fiber as the material fiber is formed by mechanically winding the heat-dividing conjugate fiber (after drawing) at about 11 to 20 pieces / inch. Mechanical crimping step of applying a crimp, carding step of passing the heat-dividing conjugate fiber after mechanical crimping through a carding machine to produce a web, and fibers constituting the web by subjecting the web to heat treatment It is manufactured by sequentially performing a non-woven fabric forming step of heat-fusing each other to form a non-woven fabric. Let's manufacture a heat-fused ultrafine fiber non-woven fabric using the above-mentioned conventional heat-dividing conjugate fiber as a material fiber. In this case, the following problem occurs.

That is, the above-described conventional heat-division conjugate fiber is easily split by a mechanical impact, and when a sufficient mechanical crimp is applied to the heat-division conjugate fiber, the division proceeds in a mechanical crimp application step. As a result, NEP and cotton loss occur frequently in the carding process, and the card passing property deteriorates.
If the mechanical crimp is weakened in order to suppress the progress of the splitting of the heat-splitting conjugate fiber in the mechanical crimping step, not only the card passing property in the carding step is deteriorated, but also the fibers in the web Since the entanglement is weak, the web is easily broken when the web is transported. Furthermore, heat-dividable conjugate fibers having weak mechanical crimp are unlikely to be split by heat even in a nonwoven fabric forming step.

A first object of the present invention is to provide a heat-splitting conjugate fiber which has a good card passing property and is easy to obtain a heat-fused ultrafine fiber nonwoven fabric excellent in texture (softness and touch). It is in.

It is a second object of the present invention to provide a heat-fused ultrafine fiber nonwoven fabric which is excellent in texture (softness and touch) and can be easily manufactured at a high yield.

[0012]

The heat-splitting conjugate fiber of the present invention, which achieves the first object, contains two components of a polypropylene resin and polyethylene terephthalate. (1) The polypropylene-based resin is distributed so as to form a main segment having a shape having a pool formed at the center of the fiber and a plurality of branches radially extending from the pool toward the fiber surface. (2) wherein the polyethylene terephthalate is distributed to form a plurality of sub-segments separated by the reservoir and the branch,
And (3) the sub-segment has an average degree of curvature of 5 to 13% on the main segment side, from the boundary line with the main segment, which reaches the fiber surface from the pool.
Characterized by being formed so as to penetrate under the sword.

[0013] The heat-fused ultrafine fiber nonwoven fabric of the present invention that achieves the second object includes the ultrafine fibers generated by splitting the above-described heat-dividing conjugate fiber of the present invention.
(a) a single-layer structure composed of only the aforementioned ultrafine fibers, (b) a monolayer structure composed of a cotton blend containing at least 30 wt% of the aforementioned ultrafine fibers, or (c) a 70% by weight or more of the aforementioned ultrafine fibers. A multi-layer structure in which the fiber layers are arranged as surface layers.

[0014]

Embodiments of the present invention will be described below in detail. As described above, the heat-dividing conjugate fiber of the present invention comprises two components of a polypropylene-based resin (hereinafter abbreviated as “PP-based resin”) and a polyethylene terephthalate (hereinafter abbreviated as “PET”). Contains.

Specific examples of the above PP resin include PP resins generally used as synthetic fiber materials, that is, homopolypropylene, ethylene-propylene random copolymer, ethylene-propylene-butene 1 copolymer. Coalescence and the like. Among these PP-based resins, ethylene-propylene is used in order to obtain a heat-division conjugate fiber having a high heat division property and a high fusion strength at the time of fusion when used as a material fiber of the heat-fusion ultrafine fiber nonwoven fabric. Random copolymers are preferred. On the other hand, as the above-mentioned PET, PET generally used as a synthetic fiber material is preferable.

The heat-dividing conjugate fiber of the present invention containing the two components of the PP resin and PET has a pool formed at the center of the fiber when the cross section in the fiber diameter direction is taken. The main segment having a shape having a plurality of branch portions radially extending from the portion toward the fiber surface is formed by the above-mentioned PP-based resin, and the plurality of sub-regions separated by the pool portion and the branch portion are formed. As the segments are formed by the above PET,
These components are allocated.

Here, the “cross-section in the fiber radial direction” referred to in the present invention means that the radial cross-sectional shape of the undrawn yarn and the radial cross-sectional shape of the drawn yarn are substantially similar. It means the cross-sectional shape in the radial direction of the undrawn yarn or drawn yarn. For the same reason, the joint ratio described later means the joint ratio in an undrawn yarn or a drawn yarn.

The above-mentioned reservoir in the main segment is:
In order to prevent the main segment from being thinned in the mechanical crimping step and the carding step performed when manufacturing the heat-fused ultrafine fiber nonwoven fabric using the heat-dividing conjugate fiber of the present invention, each of the plurality of branch portions is used. It is for joining to each other. On the other hand, the plurality of branch portions in the main segment are for forming a plurality of sub-segments made of PET in cooperation with the pool.

The total number of branched portions in the main segment may be 2 or more, but from 4 to 8 in order to obtain a heat-splitting conjugate fiber which is easy to obtain a heat-fused ultrafine nonwoven fabric having excellent flexibility and touch. Is preferred. Along with this,
It is preferable that the total number of sub-segments made of PET is 2 or more, and the total number of sub-segments is 4 to 8 as in the case of the main segment. The ratio of the sum of the cross-sectional areas of the sub-segments to the cross-sectional area of the main segment when the cross section in the fiber radial direction is taken ((the former) / (the latter); hereinafter, abbreviated as “cross-sectional area ratio”). 60 / 40-30 /
It is preferably 70.

By forming the above-mentioned center-segmented main segment with a PP resin and forming the above-mentioned sub-segments with PET, it is possible to prevent the main segment from being thinned in the opportunity crimping step and the carding step. Accordingly, it becomes possible to obtain a heat-dividing conjugate fiber having good card passing property.

However, it is not possible to obtain a heat-fused ultrafine fiber nonwoven fabric having an excellent texture by using the heat-dividing conjugate fiber only if the cardability of the heat-dividing conjugate fiber is good. From the viewpoint of obtaining a heat-fused ultrafine fiber nonwoven fabric having an excellent texture, it is preferable that as many ultrafine fibers having a small fineness as possible are generated from the heat-splitting conjugate fiber used as a material fiber of the heat-fused ultrafine fiber nonwoven fabric. It is desired that the main segment is thinned in the nonwoven fabric forming step, and a plurality of ultrafine fibers are newly generated from the main segment.

In the heat-splitting conjugate fiber of the present invention, the main segment made of PP resin and the sub-segment made of PET are so formed that the main segment is thinned in the nonwoven fabric forming step and a plurality of ultrafine fibers are newly generated. Is a specific state, that is, when taking a cross-section in the fiber radial direction, of the boundary line between the main segment and the sub-segment, the one reaching the fiber surface from the above-mentioned reservoir portion on the main segment side. It is formed in a state in which it is indented below an average curvature of 5 to 13%.

Here, the “average degree of curvature of the boundary line between the main segment and the sub-segment that reaches the fiber surface from the pool portion” in the present invention refers to the following procedure (1).
Means the value measured according to (4).

(1) As shown in FIG. 1, for a certain sub-segment 1a, (i) the point X _a closest to the reservoir 2a, and (ii) the boundary between the sub-segment 1a and the main segment 2 on the fiber surface. seeking a point Y _a1, Y _a2, further line X _a -Y _a1 connecting said point X _a and the boundary points Y _a1
Determining the maximum distance D _a1 between the arc X _a -Y _a1 and. Also,
Line X _a -Y connecting said boundary points Y _a2 and the point X _a
determining the maximum distance D _a2 between _a2 and an arc X _a -Y _a2. (2) Percentage of the maximum distance D _{a1 to} the radius R of the fiber (meaning １ ／ of the fiber diameter) (D _a1 / R)
× 100 (%) is obtained, and the degree of curvature of the arc X _a −Y _a1 is calculated. The percentage of the maximum distance D _a2 to the radius R of the fiber (D _a2 /
R) × 100 (%) is obtained and set as the curvature of the arc X _a −Y _a2 . (3) For the other sub-segments 1b, 1c, 1d,
Similarly, two curvatures are obtained. (4) The average value of the degrees of curvature obtained in the above (2) and (3) is obtained and defined as the “average degree of curvature” in the present invention.

As is clear from the above description of "the average curvature of the boundary line between the main segment and the sub-segment that reaches the fiber surface from the pool portion", the heat-splitting composite of the present invention is clear. The main segment and the sub-segment of the fiber are formed such that a part thereof is exposed to the fiber surface when the cross section in the fiber radial direction is taken.

In the heat-splitting conjugate fiber of the present invention, the sub-segment made of PET, which is a low heat shrinkage component, is indented on the side of the main segment made of PP resin, which is a high heat shrinkage component, as described above. The main segment is thinned by the heat treatment in the forming step, and a plurality of ultrafine fibers can be newly generated from the main segment. As a result, by using the heat-dividing conjugate fiber of the present invention as a material fiber, it becomes easy to obtain a heat-fused ultrafine fiber nonwoven fabric having an excellent texture.

At this time, if the ratio of the pool portion to the fiber diameter of the heat-dividing conjugate fiber is too large, it becomes difficult to make the main segment thin in the nonwoven fabric forming step. On the other hand, if the ratio of the pool portion to the fiber diameter of the heat-dividing conjugate fiber is too small, it is difficult to suppress the main segment from being thinned in the mechanical crimping step or the carding step.

From these viewpoints, in the heat-division conjugate fiber of the present invention, it is preferable that the ratio of the joint portion indicated by the ratio of the pool to the fiber diameter is approximately 5 to 13%. The bonding portion ratio is more preferably 7 to 10%, and particularly preferably 7 to 9%.

Here, the term "joint portion ratio" as used in the present invention means a percentage of the diameter of the pool portion with respect to the fiber diameter, and the diameter of the pool portion is, as shown in FIG.
Point X closest to pool 2a for 1b, 1c, 1d
_a , _Xb , _Xc , and _Xd are obtained, and these points _Xa
It means a value obtained by measuring the distance from the center O of the pool portion 2a for each _Xd and calculating the average value, and then doubling the average value.

If the fiber diameter of the heat-splitting conjugate fiber is too small, that is, if the fineness of the heat-splitting conjugate fiber is too small (generally less than 0.5 d), the above-mentioned joint ratio is 5%.
% Or more, the card passing property in the carding step performed when manufacturing the nonwoven fabric is deteriorated regardless of the properties of the heat splittable conjugate fiber. If the fiber diameter of the heat-division conjugate fiber is too large, that is, if the fineness of the heat-division conjugate fiber is too large (approximately 16d or more), the main segment becomes thin in the mechanical crimping step and the carding step. Even if this can be suppressed, the fineness of the PP-based fiber or the PET-based fiber generated by the splitting of the thermally splittable conjugate fiber is too large to be called the ultrafine fiber.

Therefore, the fineness of the heat splittable conjugate fiber of the present invention is preferably 1.5 to 10 de, and
It is more preferable to set it to 5.0 de. Further, the fineness of the main segment made of the PP-based resin is preferably 40 to 70% of the fineness of the heat-division conjugate fiber.

When the heat-splitting conjugate fiber of the present invention having the above-described fiber cross-sectional shape and the above-mentioned joint ratio is used as a material fiber to produce a heat-fused ultrafine fiber nonwoven fabric, one of the sub-segments made of PET is used. In the carding step, the portion mainly peels off and divides from the vicinity of the apex of the bent portion generated by the application of the mechanical crimp, and generates an ultrafine fiber. However, since the fiber made of PET has a relatively small frictional resistance on its surface, there is substantially no occurrence of NEP or cotton loss and deterioration of card passing property. Further, as described above, the main segment made of the PP-based resin does not substantially become thin until the carding step is completed.

Therefore, when a heat-fused nonwoven fabric is to be obtained by using the heat-dividing conjugate fiber of the present invention, a good card passing property can be obtained. Further, since the number of mechanical crimps can be generally set to 11 to 20 pieces / inch as in the related art, a web in which fibers are sufficiently entangled can be obtained by performing the carding step. Therefore, when the obtained web is transported, the web is less likely to break.

Further, in the non-woven fabric forming step performed after the carding step, while the sub-segments are further separated and split, the main segments are split by heat shrinkage, and ultrafine fibers made of PP resin are newly formed. Occurs. As a result, it becomes possible to easily obtain a heat-fused ultrafine fiber nonwoven fabric having an excellent texture.

If the number of mechanical crimps applied in the mechanical crimp applying step is approximately 11 to 20 pieces / inch, the heat splittable composite fiber of the present invention is subjected to the heat crimping after the mechanical crimp is applied. In most of the staple fibers obtained by cutting the splittable conjugate fiber into a predetermined length, at least one portion of the staple fiber generated by mechanical crimping and the portion excluding the vicinity of the vertex of the bent portion is in an undivided state, and the fiber cross-section structure in an undivided state Has been maintained.

The heat-splitting conjugate fiber of the present invention having the above-mentioned advantages can obtain a desired undrawn yarn by appropriately selecting the shape of the splittable conjugate spinneret and the discharge viscosities of the PP resin and PET. It can be obtained by stretching the drawn yarn to about 2 to 5 times, or by cutting it to 2 to 10 cm after drawing to obtain a staple fiber.

Next, the heat-fused ultrafine fiber nonwoven fabric of the present invention will be described. The heat-fused ultrafine fiber nonwoven fabric of the present invention contains, as described above, the ultrafine fibers generated by splitting the above-described heat-dividing conjugate fibers of the present invention, and (a) a single layer composed of only the ultrafine fibers described above. Structure, (b) 3
Characterized in that it has a single-layer structure composed of a blended cotton containing 0 wt% or more, or (c) a multi-layer structure in which a fiber layer containing 70 wt% or more of the ultrafine fibers is arranged as a surface layer. is there.

Here, the reason for setting the lower limit of the content of the ultrafine fibers in the heat-fused ultrafine fiber nonwoven fabric of (b) to 30 wt% is that when the content of the ultrafine fibers is less than 30 wt%, the texture ( This is because it becomes difficult to obtain a heat-fused ultrafine fiber nonwoven fabric having excellent flexibility and touch feeling. More preferably, the content is 50 wt% or more.

In the case of obtaining the heat-fused microfiber nonwoven fabric of the above (b), the material fibers other than the above-described heat-division conjugate fiber of the present invention include, for example, the material fibers other than the heat-division conjugate fiber of the present invention. Heat-splitting conjugate fiber, heat-fusible conjugate fiber of PP / high-density polyethylene, heat-fusible conjugate fiber of PP / ethylene copolymerized PP, PP / ethylene-butene-1 copolymerized P
P-based heat-fusible conjugate fibers, PET / high-density polyethylene-based heat-fusible conjugate fibers, polyester, PP fibers, rayon, and the like can be used.

On the other hand, in the heat-fused ultrafine fiber nonwoven fabric of (c), the surface layer on at least one main surface side of the heat-fused ultrafine fiber nonwoven fabric includes the above-mentioned fiber layer containing 70 wt% or more of the ultrafine fibers. As long as it is formed, 3
In order to obtain a heat-fused microfiber nonwoven fabric excellent in texture in a nonwoven fabric having a multilayer structure of two or more layers, it is necessary to form each of the surface layers on both main surfaces of the heat-fused microfiber nonwoven fabric with the above-described fiber layer. Is preferred.

The reason for setting the lower limit of the content of the ultrafine fibers in the fiber layer (surface layer) to 70% by weight is that when the content of the ultrafine fibers is less than 70% by weight, the texture (softness and feel) is reduced. This is because it becomes difficult to obtain a heat-fused ultrafine fiber nonwoven fabric excellent in (1).

In the case where the content of the ultrafine fibers in the fiber layer (surface layer) is set to 70% by weight or more and less than 100% by weight, the heat splitting of the present invention described above among the material fibers of the fiber layer (surface layer) is performed. As material fibers other than conductive composite fibers,
For example, a heat-splitting conjugate fiber other than the heat-splitting conjugate fiber of the present invention, a heat-fusible conjugate fiber of PP / high-density polyethylene, a heat-fusible conjugate fiber of PP / ethylene copolymer PP,
A heat-fusible conjugate fiber of PP / ethylene-butene-1 copolymer PP, a heat-fusible conjugate fiber of PET / high-density polyethylene, polyester, PP fiber, rayon and the like can be used.

The number of layers of the heat-fused ultrafine fiber nonwoven fabric of the above (c) may be two or three or more.
The number of the layers can be appropriately selected according to the intended use of the heat-fused ultrafine fiber nonwoven fabric. At this time, the layers other than the above-mentioned fiber layer (surface layer) are formed so that a heat-sealed nonwoven fabric is obtained.
By one or more heat fusible fibers or
It is preferable that the fiber is formed of a cotton blend containing about 50% by weight or more of one or more kinds of heat-fusible fibers. The proportion of the above-mentioned fiber layer (surface layer) in the heat-fused microfiber nonwoven fabric is appropriately selected according to the feeling required according to the use of the heat-fused microfiber nonwoven fabric, the strength of the nonwoven fabric, and the like. When the intended heat-fused microfiber nonwoven fabric is used for disposable items used for direct contact with the human body, such as disposable diapers and sanitary products, the above-mentioned fibers occupying the heat-fused microfiber nonwoven fabric The ratio of the layer (surface layer) can be selected within a range of about 30 to 70 wt%.

The heat-fused microfine nonwoven fabric of any of the above (a) to (c) can be obtained in the same manner as the conventional heat-fused microfine nonwoven fabric, except that the above-mentioned material fibers are used. At this time, the basis weight of the heat-fused ultrafine fiber nonwoven fabric can be appropriately selected according to the intended use. Like disposable diapers and sanitary products, in order to obtain a heat-sealing microfibrous non-woven fabric used as a surface material for disposable for use in applications where direct contact with the human body is generally selected within the range of 10 to 50 g / m ² Is done.

In the production of the heat-fused ultrafine fiber nonwoven fabric of the present invention, the material fibers are generally added in the same manner as in the prior art.
Even if a mechanical crimp of pieces / inch is provided, good card passing properties can be obtained as described above. In the nonwoven fabric forming step, the main segment of the thermally splittable conjugate fiber of the present invention used as the material fiber of the heat-fused ultrafine fiber nonwoven fabric is thinned, and ultrafine fibers made of PP resin are newly generated.

Therefore, the heat-fused ultrafine fiber nonwoven fabric of the present invention can be easily manufactured with a high texture (flexibility and tactile sensation) at a high yield. And among the heat-fused ultrafine fiber nonwoven fabrics of the present invention, the heat-fused ultrafine fiber nonwoven fabric of (b) or (c) is the aforementioned (a)
Has the advantage that it is easier to obtain a nonwoven fabric having a higher nonwoven fabric strength than the heat-fused ultrafine fiber nonwoven fabric.

[0047]

Hereinafter, embodiments of the present invention will be described.
With respect to the measurement items or evaluation items in each embodiment, the measurement method or evaluation method will be described in advance.

1. Bonding ratio 1 mm thick plate with pinholes (hereinafter referred to as
It is called "pinhole plate". ) Is prepared, and the pinholes formed in the pinhole plate are filled with undrawn yarns together with fine fiber rayon fibers, and these fibers are cut along the upper and lower surfaces of the pinhole plate. A cross section of the undrawn yarn in the fiber diameter direction was photographed using an optical microscope, and the diameter of the pool and the fiber diameter were determined from the photograph, and calculated from these values. However, when the main segment was formed by PET without forming the main segment by the PP resin, the ratio of the pool occupying the fiber diameter was calculated, and a minus sign was given to this value to obtain the joint ratio. .

2. The number of crimps was determined by the method of JIS L1015.

3. Card Passability A visual evaluation was made based on the following criteria. ：: There is almost no cotton fall or nep, and the web does not break. ：: Cotton fall or nep slightly occurred. X: Cotton shedding or NEP occurs frequently or the web breaks.

4. Division ratio of heat-division conjugate fiber in web The heat-division conjugate fiber of the present invention used as a material fiber was calculated by the following equation.

(Equation 1) Here, Sd, B and F in the above formulas are obtained by inserting a web into a polyurethane tube, filling the web, cutting the tube perpendicular to the longitudinal direction of the tube, and observing the cross section with a scanning electron microscope (SEM). A cross-sectional photograph having a photographing area of about 50 undivided fibers was photographed and obtained from this photograph. As is apparent from the above equation, when the main segment is thinned and new ultrafine fibers are generated from the main segment, the division ratio exceeds 100%.

5. Splitting ratio of heat-splitting conjugate fiber in nonwoven fabric Calculated in the same manner as in 4 above.

6. Non-woven fabric strength (1) MD non-woven fabric strength The length direction is matched with the direction parallel to the fiber orientation of the non-woven fabric (MD direction), and a measurement sample with a width of 50 mm is cut out.
Orientec Co., Ltd. tensile tester (Tensilon R
It was measured using a TM-250) under the conditions of a distance between chucks of 100 mm and a pulling speed of 50 mm / min. (2) Non-woven fabric strength in the CD direction A length of the non-woven fabric is aligned with a direction perpendicular to the fiber orientation of the non-woven fabric (a direction orthogonal to the CD direction), and a sample for measurement having a width of 50 mm is cut out. The measurement was performed under the conditions of a distance between chucks of 60 mm and a pulling speed of 50 mm / min.

7. Hand (Softness and Touch) A sensory test was conducted by five panelists on the softness and touch of the nonwoven fabric, and the results were evaluated based on the following criteria. A: Very good. ○: Good.

Example 1 (1) Production of heat-splitting conjugate fiber First, MF was used as a PP resin as a material of the main segment.
An ethylene-propylene random copolymer having an R of 24 (hereinafter abbreviated as “co-PP”; Y, manufactured by Idemitsu Petrochemical Co., Ltd.)
2035G) and PE, which is the material of the sub-segment,
As T, each having an IV [η] of 0.65 (Semi-Dal PET manufactured by Asahi Kasei Corporation) was melt-spun under the conditions shown in Table 1, and as shown in Table 1, the cross-sectional area ratio was 50/50.
Thus, a multilayer bonded conjugate fiber (unstretched yarn) having a joint ratio of 7.3% and an average curvature of 7.1% according to the present invention and having a fineness of 10.6 de was obtained.

In this conjugate fiber, when the cross section in the fiber radial direction is taken, a pool formed at the center of the fiber and four branches radially extending from the pool toward the fiber surface are formed. The co-PP is distributed so as to form a main segment having the same shape, and the PET is distributed so as to form four sub-segments separated by the pool portion and the branch portion.

The cross-sectional shape (cross-sectional shape in the fiber diameter direction) of each of the four branched portions in the main segment exhibits a trumpet shape extending from the pool portion to the fiber surface, and the tip of each branched portion reaches the fiber surface. . The tip of each sub-segment also reaches the fiber surface.

Next, the above undrawn yarn was drawn 3.6 times to obtain a drawn yarn of 3.5 de, which was mechanically crimped at 15 pieces / inch, dried, and dried to a fiber length of 44 mm. By cutting, a staple fiber consisting of one of the thermally splittable conjugate fibers of the present invention was obtained.

(2) Production of heat-fused ultrafine fiber nonwoven fabric First, the staple fibers obtained in the above (1) were collected by a conventional method to obtain raw cotton, and the raw cotton was passed through a roller card machine to obtain a web. Table 1 also shows the evaluation results of the card passing property and the splitting ratio of the heat splittable conjugate fiber in the web at this time. Next, the web was formed into a nonwoven fabric by an embossing roll fusing machine heated to 125 ° C. to obtain a heat-fused ultrafine fiber nonwoven fabric having a basis weight of 25 g / m ² . Table 1 also shows the results of the strength and division ratio of the nonwoven fabric measured for the heat-fused microfiber nonwoven fabric and the evaluation results of the texture.

Example 2 (1) Production of heat-dividing conjugate fiber The cross-sectional area ratio was 50/50 under the melt spinning conditions shown in Table 1.
Thus, a multilayer bonded conjugate fiber (undrawn yarn) having a joint ratio of 8.9% and an average curvature of 8.5% according to the present invention having a fineness of 10.6 de (undrawn yarn) was obtained. It was drawn by a factor of 0.6 to obtain a drawn yarn of 3.5 de. Then, 1
After giving a mechanical crimp of 1 piece / inch, the fiber was dried and cut into a fiber length of 44 mm to obtain a staple fiber composed of one of the thermally splittable conjugate fibers of the present invention.

(2) Production of heat-fused ultrafine fiber non-woven fabric The same conditions as in Example 1 (2) were used except that the staple fiber obtained in the above (1) was used as a material fiber, and the basis weight was 25 g / m ^2. Was obtained. Table 1 also shows the evaluation results and the measurement results of the same items as those evaluated and measured in Example 1 for the card permeability and the web and the heat-fused ultrafine fiber nonwoven fabric at this time.

Example 3 (1) Production of heat-dividing conjugate fiber The cross-sectional area ratio was 50/50 under the melt spinning conditions shown in Table 1.
Thus, a multilayer bonded conjugate fiber (undrawn yarn) having a joint ratio of 6.2% and a fineness of 10.6 de having an average curvature of 7.0% according to the present invention and having an average curvature of 7.0% was obtained. It was drawn by a factor of 0.6 to obtain a drawn yarn of 3.5 de. Then, 1
After giving a mechanical crimp of 1 piece / inch, the fiber was dried and cut into a fiber length of 44 mm to obtain a staple fiber composed of one of the thermally splittable conjugate fibers of the present invention.

(2) Production of heat-fused ultrafine fiber non-woven fabric Under the same conditions as in Example 1 (2) except that the staple fiber obtained in (1) above was used as a material fiber, the basis weight was 25 g / m ^2. Was obtained. Table 1 also shows the evaluation results and the measurement results of the same items as those evaluated and measured in Example 1 for the card permeability and the web and the heat-fused ultrafine fiber nonwoven fabric at this time.

Example 4 (1) Production of heat-dividing conjugate fiber The cross-sectional area ratio was 50/50 under the melt spinning conditions shown in Table 1.
Thus, a multilayer bonded conjugate fiber (unstretched yarn) having a joint ratio of 11.0% and a fineness of 10.6 de having an average curvature of 12.0% according to the present invention is obtained. It was drawn by a factor of 0.6 to obtain a drawn yarn of 3.5 de. Then, after giving a mechanical crimp of 13 pieces / inch to the drawn yarn, it was dried and cut into a fiber length of 44 mm to obtain a staple fiber composed of one of the heat splittable conjugate fibers of the present invention.

(2) Production of heat-fused ultrafine fiber non-woven fabric Under the same conditions as in Example 1 (2) except that the staple fiber obtained in (1) above was used as a material fiber, the basis weight was 25 g / m ^2. Was obtained. Table 1 also shows the evaluation results and the measurement results of the same items as those evaluated and measured in Example 1 for the card permeability and the web and the heat-fused ultrafine fiber nonwoven fabric at this time.

Example 5 (1) Production of heat-dividing conjugate fiber The cross-sectional area ratio was 50/50 under the melt spinning conditions shown in Table 1.
Thus, a multilayer bonded conjugate fiber (undrawn yarn) having a joint ratio of 13.7% and a fineness of 10.6 de having an average curvature of 14.5% as referred to in the present invention is obtained. It was drawn by a factor of 0.6 to obtain a drawn yarn of 3.5 de. Then, after applying a mechanical crimp of 11 pieces / inch to the drawn yarn, it was dried and cut into a fiber length of 44 mm to obtain a staple fiber composed of one of the heat-dividable conjugate fibers of the present invention.

(2) Production of heat-fused ultrafine fiber nonwoven fabric The same conditions as in Example 1 (2) were used except that the staple fiber obtained in the above (1) was used as a material fiber, and the basis weight was 25 g / m ^2. Was obtained. Table 1 also shows the evaluation results and the measurement results of the same items as those evaluated and measured in Example 1 for the card permeability and the web and the heat-fused ultrafine fiber nonwoven fabric at this time.

Comparative Example 1 (1) Production of heat-splitting conjugate fiber First, PET was used as the material of the main segment (the same as that used in Example 1 as the material of the sub-segment)
And a material having an MFR of 24
Each o-PP (same as that used as the material of the main segment in Example 1) was melt-spun under the conditions shown in Table 1, and the cross-sectional area ratio was 50/50 as shown in Table 1.
At 50, the joint ratio is -6.4%, and the average degree of curvature referred to in the present invention is -9.5% (because the material of the main segment and the material of the sub-segment are reversed from those specified in the present invention). ,
It shall be indicated by a negative value. ), Which is a multilayer bonded conjugate fiber (undrawn yarn) having a fineness of 10.6 de. Then, after giving a mechanical crimp of 11 pieces / inch to the drawn yarn, it was dried and cut into a fiber length of 44 mm to obtain a staple fiber.

(2) Production of heat-fused ultrafine fiber nonwoven fabric The staple fiber obtained in the above (1) was used as a material fiber, and the basis weight was 25 g / m ^{2 under} the same conditions as in Example 1 (2). When an attempt was made to obtain a heat-fused ultrafine fiber non-woven fabric, the production of the non-woven fabric was stopped because the yield decreased due to the occurrence of neps and cotton loss in the carding step. Table 1 also shows the evaluation results or measurement results for the same items as those evaluated or measured in Example 1 for the card passability and the web at this time.

[0070]

[Table 1]

As shown in Table 1, Examples 1 to 5
The heat splittable conjugate fiber of the present invention obtained in each of Examples 1 and 2 has a good card passing property, and the heat-fused ultrafine fiber nonwoven fabric of the present invention obtained in these Examples has excellent texture (softness and tactile sensation). I have. On the other hand, since the main segment is formed of PET and the sub-segment is formed of the PP resin, the heat-dividing conjugate fiber obtained in Comparative Example 1 has an absolute value of the joint ratio and the heat-dividing conjugate fiber in the web. In spite of the fact that the splitting ratio is the same as that of the thermally splittable conjugate fiber obtained in Example 1, ultrafine fibers made of PP resin are produced in the carding step, and the presence of the ultrafine fibers frequently causes neps and falling surfaces. As a result, the card passability deteriorated.

Example 6 Under the same conditions as in Example 1 (1), a staple fiber consisting of one of the heat-splitting conjugate fibers of the present invention was obtained. Fineness 2d made of ethylene copolymerized PP heat-fusible composite fiber
Staple fiber (P made by Ube Nitto Kasei Co., Ltd.)
(R-UF; length 38 mm) was mixed at a ratio of 30 parts by weight, and then a web was produced by a conventional method. Then, this web was formed into a nonwoven fabric under the same conditions as in Example 1 (2) to obtain a heat-fused ultrafine fiber nonwoven fabric having a basis weight of 25 g / m ² . The same items as those evaluated or measured in Example 1 for the heat-fused microfiber nonwoven fabric described above (excluding the division ratio).
Table 2 shows the evaluation results or the measurement results of

Example 7 A staple fiber (hereinafter, referred to as "staple fiber I") comprising one of the heat-splitting conjugate fibers of the present invention was obtained under the same conditions as in Example 1 (1). The same concentric sheath-core PP / ethylene copolymer P as used in Example 6 was used.
A staple fiber (hereinafter, referred to as “staple fiber II”) made of a P-based heat-fusible conjugate fiber was prepared. Next, using two card machines, the upper layer is made up of only the above-mentioned staple fiber I and has a basis weight of 10 g / m ^2.
In this case, a web having a two-layer structure in which the lower layer was a layer having a basis weight of 20 g / m ² consisting only of the staple fiber II was obtained. Thereafter, the web was formed into a nonwoven fabric under the same conditions as in Example 1 (2) to obtain a heat-fused ultrafine fiber nonwoven fabric having a basis weight of 30 g / m ² . Table 2 shows the evaluation results or measurement results for the same items (excluding the division ratio) that were evaluated or measured in Example 1 for the above heat-fused ultrafine fiber nonwoven fabric.

[0074]

[Table 2]

As shown in Table 2, Examples 6 and 7
Each of the heat-fused ultrafine fiber nonwoven fabrics obtained in the above is excellent in texture (flexibility and tactile sensation). Further, as is clear from the comparison between these heat-fused ultrafine fiber nonwoven fabrics and the heat-fused ultrafine fiber nonwoven fabric obtained in Example 1, each heat-fused ultrafine fiber nonwoven fabric obtained in Examples 6 to 7 was It is superior to the heat-fused microfiber nonwoven fabric obtained in Example 1 in the strength of the nonwoven fabric.

[0076]

As described above, according to the present invention, it is easy to obtain a heat-fused ultrafine fiber nonwoven fabric having excellent texture (softness and touch) at a high yield. For example, it becomes possible to provide the surface material of disposable articles used for the purpose of directly touching the human body at a lower cost.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a heat-division conjugate fiber 1 of the present invention for explaining how to determine the average degree of curvature and the joint ratio in the present invention.
FIG. 3 is a diagram schematically showing a cross section of a fiber in a fiber radial direction.

[Explanation of symbols]

1a, 1b, 1c, 1d: sub-segment, 2: main segment, 2a: pool portion.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI D06M 10/00 D06M 10/00 Z

Claims (3)

[Claims] When a cross section in the fiber diameter direction is taken, the polypropylene resin contains two components of a polypropylene resin and polyethylene terephthalate. (2) the polyethylene terephthalate is separated by the pool and the branch, the main segment having a shape having a plurality of branches radially extending from the portion toward the fiber surface. The sub-segments are distributed so as to form a plurality of sub-segments, and (3) the sub-segments which reach the fiber surface from the pool portion among the boundaries with the main segment are the main segments. Average curvature 5-1 on segment side
A heat-dividing conjugate fiber formed so as to indent below 3%. 2. The heat-dividing conjugate fiber according to claim 1, wherein a joint portion ratio indicated by a ratio of the pool portion to the fiber diameter is 5 to 13%. 3. The heat-dividing conjugate fiber according to claim 1 or 2, comprising a microfiber produced by splitting, (a) a single-layer structure composed of only the microfiber, and (b) the (C) a multilayer structure in which a fiber layer containing at least 70 wt% of the ultrafine fibers is arranged as a surface layer. Heat-fused microfiber nonwoven fabric.