JP4791173B2 - Split composite short fiber and short fiber nonwoven fabric - Google Patents

Description

The present invention is a split type composite fiber composed of two components of a polyamide polymer and a polyolefin polymer, and after splitting, becomes a polyamide short fiber and a polyolefin short fiber, and the split ratio of both components is high, has excellent split resistance, Ru der relates splittable composite short fibers used in the dry nonwoven fabric according to air-laid process.

  In various fields including the sanitary materials field, short fibers made of thermoplastic resin such as polyester, polyamide, polyolefin, etc. are used and dispersed uniformly. Adhesion with binder resin, adhesion with hot air, pressure bonding with hot roll, high pressure Dry nonwoven fabrics and wet nonwoven fabrics obtained by water flow or entanglement with metal needles are used.

  Among them, there is a high demand for nonwoven fabrics that are excellent in soft texture, low air permeability, drapeability, wiping properties, etc., and in order to make such nonwoven fabrics, it has been proposed to use nonwoven fabrics made of ultrafine fibers. For example, Patent Document 1 proposes that a high-pressure liquid flow is jetted onto divided composite fibers deposited in a web shape to divide the fibers into a nonwoven fabric made of ultrafine fibers.

  Patent Document 2 and Patent Document 3 propose a nonwoven fabric made of ultrafine fibers obtained by obtaining a nonwoven fabric made of composite fibers and then dissolving one component of the composite fibers with a solvent.

  However, any nonwoven fabric has the disadvantages that the processing speed when dividing or eluting the composite fiber is slow, the processing method is complicated and expensive, and the composite fiber is not sufficiently divided or eluted. The quality of the nonwoven fabric was not satisfactory.

  Moreover, there exists an airlaid method as a method of obtaining a dry nonwoven fabric using a short fiber. The airlaid method employs a method in which fibers are defibrated and transported in a flow of air, passed through a screen having a wire mesh or pores, and then dropped and deposited on a wire mesh. In the conveying, dispersing, and laminating processes, the friction between the fibers and the fibers and the fibers and the metal is large, and static electricity is likely to be generated.

  When a fiber lump is formed, the passability in each process deteriorates and the operability is deteriorated. In addition, even in the obtained non-woven fabric, the accumulated fibers become non-uniform, resulting in a non-uniform non-woven fabric, and the product quality is remarkably lowered. .

  Today, many functional thermoplastic resins are used to differentiate products such as higher grades and higher functionality, including those that require low-temperature processing, thermoplastic resins with high tackiness, etc. Are used, and fibers having higher fiber-fiber friction and fiber-metal friction than conventional fibers are used. Further, in order to improve manufacturing processing efficiency, the processing speed is increased. Due to these factors, the amount of static electricity generated in the manufacturing process by the airlaid method is increased, and the generation of fiber mass is also increased.

The nonwoven fabric obtained by such an airlaid method is also required to be a nonwoven fabric composed of ultrafine fibers and having sufficient quality. However, when a fiber lump is generated due to the generation of static electricity, the splitting rate of the split-type composite fibers decreases, and therefore there is a problem that it is difficult to obtain a high-quality nonwoven fabric that is made of ultrafine fibers and has no spots. It was.
JP-A-62-133164 JP-A-62-78213 JP 56-154512 A

  The present invention solves the above-mentioned problems, and particularly in the production of dry nonwoven fabrics where fiber lumps are likely to occur due to the generation of static electricity, the split rate by air agitation is high, and by dividing easily into ultrafine fibers, A split type composite short fiber that is made of ultra fine fibers, has few undivided parts, is excellent in uniformity, has a soft texture, and can obtain a low air permeability nonwoven fabric, and an ultra fine split from this split type composite short fiber It is a technical problem to provide a short fiber nonwoven fabric containing fibers.

  The present inventors have reached the present invention as a result of intensive studies to solve the above problems.

That is, the gist of the present invention is the following (a) to (c) .
(A) A split type composite fiber composed of two components of a polyamide-based polymer A and a polyolefin-based polymer B, the fiber for obtaining a dry nonwoven fabric by the airlaid method, and with respect to the longitudinal direction of the fiber In the cross section cut perpendicularly, it has a shape in which a plurality of polyamide polymers are arranged in contact with the periphery of the polyolefin polymer (except that the cross-sectional shape of the composite fiber is a circular cross section) , and air . and a stirring split ratio is 65% or more, the fiber length is 1.0～30Mm, single yarn fineness of Ri 0.5~20dtex der, the fibers, crimping has been granted, crimp form of single yarn crimp portion The ratio of the height (H) to the base (L) (H / L) of the triangle connecting the peak of the peak and the bottom of the valley adjacent to the peak satisfies the following formula (1) A split-type composite short fiber characterized by:
(1) Formula: 0.01T + 0.10 ≦ H / L ≦ 0.02T + 0.25
T is the number of decitex (dtex) of single yarn fineness
(A) A method for producing a short fiber nonwoven fabric, wherein a web is prepared by the airlaid method using the split type composite short fibers of (a) to obtain a nonwoven fabric.
(C) A short fiber nonwoven fabric obtained by the method for producing a short fiber nonwoven fabric of (a).
(A) A short fiber nonwoven fabric comprising 30% by mass or more of polyamide short fibers having a fiber length of 1.0 to 30 mm and a single yarn fineness of 0.05 to 5 dtex made of a polyamide-based polymer.

  The split type composite short fiber of the present invention has a high split ratio by air agitation, and is easily split into ultrafine fibers of polyamide short fibers and polyolefin short fibers. Can also be suitably used. And it becomes possible to obtain the nonwoven fabric which consists of an ultrafine fiber with few undivided parts, excellent uniformity, a soft texture, and low air permeability.

  Moreover, since the short fiber nonwoven fabric of the present invention contains the ultrafine fibers of polyamide short fibers divided from the split composite short fibers of the present invention, it has uniformity, soft texture and low air permeability. It is a nonwoven fabric and can be used for various purposes.

  Hereinafter, the present invention will be described in detail.

The split type composite short fiber (hereinafter abbreviated as composite short fiber) of the present invention comprises two components, a polyamide polymer (referred to as polymer A) and a polyolefin polymer (referred to as polymer B), and is a fiber. In the cross section cut perpendicularly to the longitudinal direction, the polymer B has a shape in which a plurality of polymers A are arranged in contact with the periphery of the polymer B (except that the cross-sectional shape of the composite fiber is a circular cross section) .)

  That is, as shown in FIGS. 1 to 3, a polymer B is mainly arranged around the polymer B, and the polymer A shown in FIG. Four are arranged in contact with the periphery. The one shown in FIG. 2 is one in which eight polymers A are arranged in contact with the periphery around the polymer B, and the one shown in FIG. 3 is the polymer A around the polymer B. Twelve are arranged in contact with the periphery.

  The number of the polymers A arranged around the polymer B is preferably 2 to 20, and more preferably 3 to 8. The shapes of the polymers A and B are not particularly limited, and may be not only round or elliptical shapes but also polygonal shapes such as triangles and squares. These shapes may be appropriately selected in consideration of the shape and fineness of the fiber obtained after the division and the operability during spinning.

  Furthermore, the composite ratio of the polymer A and the polymer B may be appropriately adjusted in consideration of the use of a product such as a nonwoven fabric to be obtained, but the ratio of the polymer A may be 50% by mass or more. Among these, 75% by mass or more is preferable.

  Next, the composite short fiber of the present invention has a fiber length of 1.0 to 30 mm, and a more preferable fiber length is 2 to 25 mm, more preferably 5 to 15 mm. The single yarn fineness is 0.5 to 20 dtex, preferably 1.0 to 15 dtex. The fiber length was measured based on JIS L1015 8.4.1 (average fiber length) A method, and the single yarn fineness was measured according to JIS L1015 8.5.1 (positive fineness) B method (simple method). It is measured based on.

  When the fiber length is less than 1.0 mm, the fibers tend to be fused by heat generated when the fibers are cut. On the other hand, if it exceeds 30 mm, a fiber lump due to entanglement of fibers occurs during air agitation, and the fiber division rate decreases.

  If the single yarn fineness is less than 0.5 dtex, it is not preferable from the standpoints of operability and productivity during yarn production. On the other hand, if it exceeds 20 dtex, the fineness of the fibers after the division is not sufficiently reduced, and it becomes difficult to obtain ultrafine fibers.

  Furthermore, the composite short fiber of the present invention has an air stirring division ratio of 65% or more. The air agitation division ratio indicates a ratio at which the composite fiber is divided into a polyamide short fiber made of the polymer A and a polyolefin short fiber made of the polymer B when stirred in the air. That is, the air stirring division ratio in the present invention is measured and calculated as follows.

The composite short fiber of the present invention was introduced into the stirring tank 1 by the air flow from the sample feeding blower 3 to the stirring tank 1 using a simple air flow stirring tester as shown in FIG. An air flow of 20 m / sec is blown and stirred in the stirring tank 1 for 1 minute. The short fibers after stirring are taken out from the sampling port 4, and arbitrary 10 positions are selected, and an enlarged photograph of the fiber cross section is taken. The number of the polymer A (polyamide short fiber) divided from the composite fiber is counted in the 10 photographs taken, and the following formula is calculated from the number of arrays of the polymer A before the division.
Air stirring division ratio (%) = (number of divided polymers A / number of arrangements of polymers A before division) × 100
Example: In the schematic diagram of FIG. 5, the number of divided polymers A = 9, the number of arrays of the polymer A before dividing = 12, the dividing ratio (%) = (9/12) × 100 = 75

  When the air stirring division ratio is 65% or more, it is easily divided into ultrafine fibers of polyamide short fibers and polyolefin short fibers by air stirring. Even in the case of producing a non-divided portion, excellent uniformity, low air permeability, and soft texture nonwoven fabric can be obtained. If the air agitation division ratio is less than 65%, it is difficult to achieve the above effects. The air stirring division ratio is preferably 70% or more, and more preferably 75% or more.

  In addition, in the case of the composite short fiber in which the polymers A and B are arranged radially as shown in FIG. 4, division by air stirring becomes difficult, and the air stirring division ratio becomes low and cannot be made 65% or more.

Furthermore, the composite short fiber of the present invention has been crimped , and in particular, at the maximum peak portion of the crimped portion, the bottom point of the valley portion adjacent to the apex of the peak portion is the crimped form of the single yarn. The ratio (H / L) of the height (H) and base (L) of the triangle connecting the two points satisfies the following formula (1) .
(1) Formula: 0.01T + 0.10 ≦ H / L ≦ 0.02T + 0.25
T is the number of detexes (dtex) of single yarn fineness. By using such a shape, static electricity generation is reduced, and short fibers gather together to form a fiber mass. The rate will also be high.

  That is, when the above crimped form is satisfied, the air stirring division ratio can be set to 70% or more, which is particularly suitable when a dry nonwoven fabric is obtained by the airlaid method. Furthermore, as will be described later, when the crimped form of the composite short fiber of the present invention satisfies all the expressions (1) to (3), the air stirring division ratio can be 75% or more.

  When a dry nonwoven fabric is obtained, particularly when it is produced by the airlaid method, static electricity is generated more. As an apparatus used for this airlaid method, for example, as disclosed in Japanese Patent Laid-Open No. 5-9813, a plurality of rotating cylinders are housed in a housing, and these cylinders are rotated at a high speed to positively move to the periphery of the cylinder. An apparatus that can generate an air flow and blow the fiber component in a predetermined direction by the air flow can be mentioned. In the web formation by the airlaid method (short fiber defibration, transport, dispersion, and lamination processes), the air flow is actively generated, so that the fibers are rubbed with each other. The generation of static electricity also increases due to friction with the (metal member).

  The composite short fiber of the present invention has a specific shape of the fiber having crimps, so that in each step of web formation (defibration, conveyance, dispersion, lamination step), between fibers, between fibers and metal It is difficult to generate static electricity due to friction, and it is difficult to accumulate the generated static electricity, so that short fibers gather to form a fiber lump.

  When considering the problem of static electricity as described above, the more the number of crimps and the larger or stronger the crimps are applied, the easier it is to store electricity in terms of shape. That is, if the fiber is crimped, it exhibits a three-dimensional solid shape, so that static electricity tends to accumulate as the three-dimensional space portion increases. On the other hand, as the flat state without crimping becomes flat, it becomes more flat and less likely to accumulate static electricity. However, the number of contact points (surfaces) between fibers or between fibers and metal increases, and the generation of static electricity due to friction increases. .

  When considering the bulkiness, the bulkiness of the nonwoven fabric obtained decreases as the flat state without crimping decreases. On the other hand, the more the crimp is applied, the higher the bulkiness of the resulting nonwoven fabric, but the higher the bulkiness of the fibers. It tends to be a nonwoven fabric with poor uniformity.

  Moreover, the problem of static electricity and fiber entanglement, and the texture (bulkness and flexibility) of the resulting nonwoven fabric are also affected by the single yarn fineness. That is, in the problem of static electricity, static electricity is generated by contact between fibers or between a fiber and a metal, and thus the single yarn fineness factor that determines the size of the contact point and the contact surface is large. In addition, since a three-dimensional solid shape is formed by crimping, the single yarn fineness is a factor that determines the size of the space portion, and is a factor that determines the degree of static electricity and the degree of fiber entanglement.

  Therefore, the present inventors have considered these factors in consideration, and by making the shape of the split-type composite short fibers into a three-dimensional shape to which a specific crimp considering the single yarn fineness is given, (The prevention of static electricity and fiber entanglement and the improvement of the nonwoven fabric texture) were further improved, and further, the split-type composite short fibers were easily divided by air agitation, and the above-mentioned air agitation division ratio was further increased.

First, as shown in FIG. 6, the fiber of the present invention is a single yarn crimped form in which the peak apex P of the peak portion at the maximum peak portion of the crimped portion and the bottom points Q and R of the adjacent valley portions are two. The points are connected to form a triangle, and the ratio (H / L) of the height (H) to the base (L) of the triangle satisfies the following formula (1).
Here, when there are a plurality of peak portions in the fiber length of the fiber of the present invention, the maximum peak portion means the one having the maximum peak height (H).
(1) Formula: 0.01T + 0.10 ≦ H / L ≦ 0.02T + 0.25

  In order to express the degree of crimp, the crimp rate is generally used, but the method for measuring the crimp rate is obtained from the difference in length between when a load is applied and when there is no load. However, in the present invention, even if the expression (3) that defines the crimping rate described later is satisfied, the crimping is such that the space part of the three-dimensional shape becomes large in some crimped parts in the fiber. If there is a part where the area is large, it is easy to accumulate static electricity, and the fibers tend to be entangled. Therefore, as specified in Equation (1), by specifying the shape at the maximum peak as a crimped shape, the size of the space portion due to crimping is specified, so that static electricity and fiber entanglement It is possible to prevent the generation of fiber lumps due to.

  When H / L is too large, the space portion becomes large in the three-dimensional shape of the fiber, and static electricity is easily accumulated, and the fiber becomes entangled easily. On the other hand, if the H / L is too small, the shape of the fiber becomes nearly flat, and the contact points (surfaces) between the fibers or between the fibers and the metal increase, so static electricity is likely to be generated, and a fiber lump is generated. The air stirring division ratio also decreases. For this reason, even if division processing such as air stirring is performed, the number of undivided portions increases, and the resulting nonwoven fabric tends to be poor in uniformity.

  In addition, the measurement of H / L is as follows. First, 1 g of short fibers are collected, and 20 single fibers are arbitrarily extracted therefrom. Then, an enlarged photograph (about 10 times) is taken with respect to the taken out single fiber, and as described above from the photograph, two points of the bottom points Q and R of the valley part adjacent to the peak part P at the peak part are adjacent to the maximum peak part. A triangle is formed, and the height (H) and the base (L) of the triangle are measured, and the ratio (H / L) is calculated. In this way, 20 single fibers are measured and the average value is taken.

  Next, the composite short fiber of the present invention preferably satisfies the formula (2): 0.1T + 3.8 ≦ crimped number ≦ 0.3T + 7.3 [T is the number of dtex of the single yarn fineness]. The crimp number is measured and calculated based on JIS L1015 8.12.1 (crimp number). In addition, when the fiber length is short in the measurement of the number of crimps, it is measured on the fiber before cutting after the crimping and is converted into the number per 25 mm fiber length.

  If the number of crimps is higher than that in equation (2), the number of crimped parts that become a space part due to a three-dimensional solid shape will increase, and will be generated between fibers in the short fiber feeding, dispersion, and defibrating process by airflow This is not preferable because static electricity is easily accumulated and fibers are easily entangled with each other. On the other hand, when the value is lower than the expression (2), the crimped portion is reduced, so that the shape of the fiber is almost flat, and the number of contact points (surfaces) between the fibers or between the fiber and the metal increases, so that static electricity is easily generated. A ball-shaped fiber lump is formed, and the air stirring division ratio is lowered, which is not preferable. For this reason, even if it performs the division | segmentation process by air stirring etc., an undivided part increases and the nonwoven fabric obtained becomes a thing with poor uniformity.

  Furthermore, it is preferable that the composite short fiber of the present invention satisfies the following formula (3): 0.8T + 0.3 ≦ crimp rate ≦ 1.0T + 4.9 [T is the decitex (dtex) number of single yarn fineness]. The crimp rate is measured and calculated based on JIS L1015 8.12.2 (crimp rate and residual crimp rate). In addition, when the fiber length is short in the measurement of the crimp rate, it is difficult to measure, and after the crimp is applied, the fiber is measured before being cut and converted to the number per 25 mm fiber length.

  When the crimping rate is higher than that of Equation (3), the space portion due to the three-dimensional solid shape increases or becomes large, and static electricity generated between the fibers in the process of feeding, dispersing, and defibrating short fibers in the air flow. Therefore, the fibers are easily entangled with each other, so that a ball-like fiber lump is generated and the air stirring division ratio is lowered, which is not preferable. On the other hand, when the value is lower than the expression (3), the shape of the fiber becomes almost flat, and the number of contact points (surfaces) between the fibers or between the fiber and the metal increases. This is not preferable because the air stirring division ratio is reduced. For this reason, even if it performs the division | segmentation process by air stirring etc., an undivided part increases and the nonwoven fabric obtained becomes a thing with poor uniformity.

  Next, as the polyamide polymer constituting the composite short fiber of the present invention, in order to stably produce the fiber, and as described later, it is considered that the divided polyamide fiber is used as the main fiber. Then, it is preferable that melting | fusing point shall be 200 degreeC or more, and it is preferable that it is 200-280 degreeC above all.

  Specific examples of the polyamide polymer include aliphatic polyamide and aromatic polyamide, and nylon 6 and nylon 66 are particularly preferable. If necessary, it may be a copolymerized polyamide obtained by copolymerizing another polyamide, or a mixture of two or more polyamides may be used.

  In addition, examples of the polyolefin polymer constituting the composite short fiber of the present invention include aliphatic α-monoolefins having 2 to 18 carbon atoms, among which polyethylene and polypropylene are preferable. If necessary, it may be a copolymerized olefin in which other olefins are copolymerized, or two or more kinds of polyolefins may be mixed and used.

  Further, in the composite short fiber of the present invention, a matting agent such as titanium oxide, an antioxidant such as a hindered phenol compound, an ultraviolet absorber, a light stabilizer, a pigment, a difficult dye, and the like, as long as the effect is not impaired. A flame retardant, an antibacterial agent, a conductivity imparting agent, a hydrophilic agent, a water absorbing agent and the like may be blended.

The composite short fiber of the present invention, the dry nonwoven fabric applications, used for producing the d Areido method. According to the airlaid method, when the fiber is transported into the production machine (preliminary defibration or air feed) or defibrated, the fiber is easily divided into polyamide short fibers and polyolefin short fibers, and a process and equipment for dividing the fibers are provided. There is no need to provide it separately, which is advantageous in terms of cost.

  In addition, the composite short fiber of the present invention may be used together with other fibers when making a nonwoven fabric, or only the composite short fiber of the present invention may be used. Among these, considering the composition of the composite short fiber of the present invention, it is preferable to obtain a nonwoven fabric using only the composite short fiber of the present invention. That is, it is preferable to use a polyamide short fiber after splitting as a main fiber and a polyolefin short fiber as a binder fiber, and heat-treat to melt the polyolefin short fiber (binder fiber) portion to obtain a nonwoven fabric.

  As described above, when the nonwoven fabric is formed using only the short fiber of the present invention, the binder fiber (polyolefin short fiber) can be easily melted and the main fiber (polyamide short fiber) can be bonded only by heat treatment with hot air. Therefore, it is possible to omit a generally performed bonding with a binder resin or a pressure bonding step with a hot roll, which is advantageous in terms of cost.

Next, the short fiber nonwoven fabric of the present invention will be described. The short fiber nonwoven fabric of the present invention is a nonwoven fabric obtained by creating a web by the airlaid method using the composite short fibers, the fiber length of the polyamide-based polymer is 1.0-30 mm, the single yarn fineness is 0.05-5 dtex It contains 30% by mass or more of polyamide short fibers.

The short fiber nonwoven fabric of the present invention is preferably a nonwoven fabric using only the above-described composite short fiber of the present invention. The polyamide short fiber is a main fiber and the polyolefin short fiber is a binder fiber. What adhered the fiber is preferable.

  The polyamide short fiber has the same single yarn shape as the composite short fiber of the present invention, and is represented by the formula (1) in the composite short fiber of the present invention (the formula (4) in the short fiber nonwoven fabric of the present invention). It is preferable to satisfy the shape, and it is further preferable to satisfy the number of crimps and the crimp rate of the expressions (2) and (3) in the composite short fiber of the present invention.

  The polyamide short fibers in the nonwoven fabric are preferably 30% by mass or more, and more preferably 40% by mass or more. When the content is less than 30% by mass, the resulting nonwoven fabric has a low proportion of ultrafine fibers (polyamide fibers), and therefore is inferior in uniformity, inferior in low air permeability and softness. Also, it tends to have poor mechanical properties.

  In the short fiber nonwoven fabric of the present invention, as long as the mass of polyamide short fibers in the nonwoven fabric is 30% by mass or more, other short fibers may be used together with the composite short fiber of the present invention. You may use for any of a main fiber and a binder fiber. In consideration of the uniformity, flexibility, etc. of the resulting nonwoven fabric, the other short fibers have the same single yarn shape as the short fibers of the present invention, and the shapes of the formulas (1) to (3) in the present invention Those satisfying the number of crimps and the crimp rate are preferred.

Next, the manufacturing method of the composite short fiber of this invention is demonstrated using an example.
A spinning hole in which a polyamide polymer and a polyolefin polymer are perforated so as to be in a shape in which a plurality of polyamide polymers are arranged in contact with the periphery of the polyolefin polymer using a commonly used composite spinning device Spin the composite.

  Then, the spun yarn is wound once without stretching. The obtained undrawn yarn is converged to form a tow of about 1 to 100 ktex, and hot drawn at a draw ratio of 2 to 6 times and a temperature of about 20 to 90 ° C. And after crimping with an indentation type crimper, a finishing oil agent is provided as needed, and it cuts into desired fiber length, and obtains the fiber of this invention.

  In order to satisfy the crimping form defined in the present invention, the stretching conditions (magnification, temperature) and the crimping conditions (nip pressure, stuffing pressure) in a crimping apparatus such as a push-in crimper are adjusted. By doing.

Next, the manufacturing method of the short fiber nonwoven fabric of this invention is demonstrated using an example.
As a preliminary opening, a simple air flow agitation tester as shown in FIG. 7 is used, and the composite short fiber of the present invention is introduced into the agitation tank 1 from the sample feeding blower 3 by an air flow, and 20 m from the agitation blower 2 The air flow of / sec is blown and stirred in the stirring tank 1 for 1 minute. Subsequently, using the simple airlaid tester shown in FIG. 8, the pre-opened fiber of the present invention is fed from the sample loading blower 13 and is rotated by the defibrating blade rotating motor 15 via the defibrating blade rotating sprocket 16. The set of the first defibrating blade 11 and the second defibrating blade 12 is defibrated and scattered and dropped. Thereby, the composite short fiber of this invention is divided | segmented into a polyamide short fiber and a polyolefin short fiber. Then, while dropping both short fibers with the suction box 14 at the bottom, they are deposited on the cotton collecting conveyor 17 moving in the direction of the arrow to create a web. Subsequently, heat treatment (heat treatment temperature: melting point of polyolefin short fibers + about 10 ° C.) is performed by a heat treatment machine 18 located downstream, and the polyolefin short fibers are melted as binder fibers to obtain a dry nonwoven fabric made of polyamide short fibers. The basis weight adjustment of the nonwoven fabric is performed by changing the moving speed of the cotton collection conveyor 17.

Next, the present invention will be specifically described with reference to examples. In addition, the measuring method of each characteristic value in an Example is as follows.
(1) Melting point The temperature which gives the extreme value of the melting absorption curve measured with a differential scanning calorimeter (DSC7 manufactured by Perkin Elmer Co., Ltd.) at a temperature rising rate of 20 ° C./min was defined as the melting point.
(2) Relative viscosity Measured at a concentration of 1 g / dl and a temperature of 25 ° C. using 96% sulfuric acid as a solvent.
(3) Melt index (MI)
Measured with ASTM D 1238.
(4) Fineness, fiber length, H / L of crimped portion, number of crimps, crimp rate Measured and calculated by the above method.
(5) Air stirring division ratio Measured and calculated by the above method.
(6) Formation of fiber lump The obtained composite short fiber is air-stirred under the same conditions and method as the air-stirring division ratio. When taking out the short fibers after stirring, 0.1 g of the short fibers were collected and spread on black paper, and the presence or absence of a fiber lump was visually evaluated.
○: No fiber lump is generated Δ: A small amount of fiber lump is generated x: A large amount of fiber lump is generated (7) Uniformity, air permeability and flexibility of the nonwoven fabric
The uniformity state of the obtained dry nonwoven fabric was observed visually, and was evaluated in three stages as follows.
○: Fully defibrated and uniform △: Partially undefibrated part ×: Insufficient defibration and non-uniformity-Air permeability-
The obtained dry nonwoven fabric was measured for air permeability using a fabric air permeability tester (AP-360 type, manufactured by Daiei Kagaku Seisaku Seisakusho), and was evaluated according to an average of 5 points as follows.
When fineness before division is 2.2 dtex ○: Air permeability is less than 20.0 cc / cm ² / sec.
Δ: The air permeability is 20.0 cc / cm ² / sec or more and less than 30.0 cc / cm ² / sec.
X: Air permeability is 30.0 cc / cm ² / sec or more.
When the fineness before division is 17.0 dtex ○: The air permeability is less than 30.0 cc / cm ² / sec.
Δ: The air permeability is 30.0 cc / cm ² / sec or more and less than 40.0 cc / cm ² / sec.
X: The air permeability is 40.0 cc / cm ² / sec or more.
-Flexibility-
The obtained wet nonwoven fabric was cut out into 20 cm × 20 cm to make a sample, and the softness was evaluated by a three-step evaluation as follows according to the touch of the panel.
○: Good △: Somewhat bad ×: Bad

Example 1
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.53 is used as polymer A, and polyethylene having a melting point of 132 ° C. and a melt index (MI) value of 20 g / min is used as polymer B. Used, melt spinning was performed under the conditions of a spinning temperature of 270 ° C., a discharge rate of 616 g / min (nylon 462 g / min, polyethylene 154 g / min) and a spinning speed of 800 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 1014 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 11.5 ktex tow and then drawn at a draw ratio of 3.45 times and a draw temperature of 50 ° C. Subsequently, crimping was applied by a push-in type crimper with a nip pressure of 0.43 MPa and a stuffing pressure of 0.15 MPa. Then, after applying an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil so as to have an adhesion amount of 0.2% by mass, it is cut into a composite short fiber having a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Obtained.
Using the simple air flow agitation tester shown in FIG. 7, only the obtained composite short fiber is introduced into the agitation tank 1 by the air flow from the sample feeding blower 3, and an air flow of 20 m / sec is applied from the agitation blower 2. The mixture was blown and stirred in the stirring tank 1 for 1 minute (preliminary opening).
Next, using a simple airlaid tester shown in FIG. 8, a dry nonwoven fabric having a basis weight of 100 g / m ² was obtained as follows. First, pre-opened composite short fibers are loaded from the sample loading blower 13 and rotated by the defibrating blade rotating motor 15 via the defibrating blade rotating sprocket 16, each having a set of five first defibrating blades 11 and second defibrating blades 12. Defibrated and scattered and dropped. Thereby, the composite short fiber was divided into a polyamide short fiber and a polyolefin short fiber. Then, the falling short fibers are sucked by the suction box 14 at the lower part and are deposited on the cotton collecting conveyor 17 that moves in the direction of the arrow to create a web. Subsequently, heat treatment (heat treatment temperature: 140 ° C.) was performed by a heat treatment machine 18 on the downstream side, and the polyolefin short fibers were melted as binder fibers to obtain a dry nonwoven fabric mainly composed of polyamide short fibers. At this time, the basis weight adjustment of the nonwoven fabric was performed by changing the moving speed of the cotton collecting conveyor 17.

Example 2 and Comparative Example 1
As shown in Table 1, composite short fibers were obtained in the same manner as in Example 1 except that the spinneret was changed so that the cross-sectional shape of the fibers was as shown in FIGS.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Examples 3-14
Various changes were made to the conditions (nip pressure, stuffing pressure) for applying crimp with the indentation type crimper as shown in Table 1, and the crimping form, number of crimps, and crimp rate shown in Table 1 were used. A composite short fiber was obtained in the same manner as in Example 1.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Example 15
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.53 is used as the polymer A, and a polypropylene having a melting point of 163 ° C. and a melt index (MI) value of 28 g / min is used as the polymer B. Used, melt spinning was performed under the conditions of a spinning temperature of 270 ° C., a discharge rate of 645 g / min (nylon 484 g / min, polypropylene 161 g / min) and a spinning speed of 800 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 1014 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 11.8 ktex tow and then drawn at a draw ratio of 3.61 times and a draw temperature of 50 ° C. Subsequently, crimping was applied using a push-in type crimper with the nip pressure of 0.45 MPa and the stuffing pressure of 0.15 MPa. Thereafter, an oil agent containing polyoxyethylene alkyl ether as a main component as a finishing oil agent was applied so that the amount of adhesion was 0.2% by mass, and then cut to form a composite short fiber having a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Got.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1 except that the heat treatment temperature by the heat treatment machine 18 was set to 170 ° C.

Comparative Example 2
A composite short fiber was obtained in the same manner as in Example 15 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape shown in FIG.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 15.

Example 16
Nylon 66 having a melting point of 257 ° C. and a relative viscosity of 2.50 is used as the polymer A, and a polyethylene having a melting point of 132 ° C. and a melt index (MI) value of 20 g / min is used as the polymer B. Used, melt spinning was carried out under the conditions of a spinning temperature of 285 ° C., a discharge rate of 652 g / min (nylon 489 g / min, polyethylene 163 g / min) and a spinning speed of 800 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 1014 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.0 ktex tow and then drawn at a draw ratio of 3.65 times and a draw temperature of 50 ° C. Subsequently, crimping was applied using a push-in crimper with a crimping condition of nip pressure 0.43 MPa and stuffing pressure 0.16 MPa. Thereafter, an oil agent containing polyoxyethylene alkyl ether as a main component as a finishing oil agent was applied so that the amount of adhesion was 0.2% by mass, and then cut to form a composite short fiber having a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Got.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Comparative Example 3
Composite short fibers were obtained in the same manner as in Example 16 except that the spinneret was changed so that the cross-sectional shape of the fibers became the shape shown in FIG. 4 as shown in Table 1.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 16.

Example 17
Nylon 66 having a melting point of 257 ° C. and a relative viscosity of 2.50 is used as the polymer A, and a polypropylene having a melting point of 163 ° C. and a melt index (MI) value of 28 g / min is used as the polymer B. Used, melt spinning was carried out under the conditions of a spinning temperature of 285 ° C., a discharge rate of 688 g / min (nylon 516 g / min, polypropylene 172 g / min) and a spinning speed of 800 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 1014 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.5 ktex tow and then drawn at a draw ratio of 3.86 times and a draw temperature of 50 ° C. Subsequently, crimping was applied using a push-in crimper with a crimping condition of nip pressure 0.43 MPa and stuffing pressure 0.16 MPa. Thereafter, an oil agent containing polyoxyethylene alkyl ether as a main component as a finishing oil agent was applied so that the amount of adhesion was 0.2% by mass, and then cut to form a composite short fiber having a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Got.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1 except that the heat treatment temperature by the heat treatment machine 18 was set to 170 ° C.

Comparative Example 4
A composite short fiber was obtained in the same manner as in Example 17 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape shown in FIG.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 17.

Example 18
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.53 is used as polymer A, and polyethylene having a melting point of 132 ° C. and a melt index (MI) value of 20 g / min is used as polymer B. Used, melt spinning was performed under the conditions of a spinning temperature of 270 ° C., a discharge rate of 424 g / min (nylon 318 g / min, polyethylene 106 g / min), and a spinning speed of 700 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 90 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.4 ktex tow and then drawn at a draw ratio of 3.95 times and a draw temperature of 55 ° C. Subsequently, crimping was applied using a push-in crimper, with the crimping conditions set to a nip pressure of 0.55 MPa and a stuffing pressure of 0.24 MPa. Thereafter, an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil agent was applied so that the adhesion amount was 0.2% by mass, and then cut to be a composite short fiber having a single yarn fineness of 17.0 dtex and a fiber length of 5 mm. Got.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Example 19, Comparative Example 5
As shown in Table 1, composite short fibers were obtained in the same manner as in Example 18 except that the spinneret was changed so that the cross-sectional shape of the fibers was as shown in FIGS.
Next, a dry nonwoven fabric was obtained in the same manner as in Example 18 using the obtained composite short fiber.

Examples 20-31
Various changes were made to the conditions (nip pressure, stuffing pressure) for applying crimp with the indentation type crimper as shown in Table 1, and the crimping form, number of crimps, and crimp rate shown in Table 1 were used. A composite short fiber was obtained in the same manner as in Example 18.
Next, a dry nonwoven fabric was obtained in the same manner as in Example 18 using the obtained composite short fiber.

Example 32
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.52 is used as polymer A, and polypropylene having a melting point of 163 ° C. and a melt index (MI) value of 28 g / min is used as polymer B. The melt spinning was performed under the conditions of a spinning temperature of 270 ° C., a discharge rate of 440 g / min (nylon 330 g / min, polypropylene 110 g / min), and a spinning speed of 700 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 90 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 11.8 ktex tow and then drawn at a draw ratio of 4.10 times and a draw temperature of 55 ° C. Subsequently, crimping was applied using a push-in crimper with the crimping conditions set to a nip pressure of 0.56 MPa and a stuffing pressure of 0.24 MPa. Thereafter, an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil agent was applied so that the adhesion amount was 0.2% by mass, and then cut to be a composite short fiber having a single yarn fineness of 17.0 dtex and a fiber length of 5 mm. Got.
Next, a dry nonwoven fabric was obtained in the same manner as in Example 18 except that the obtained composite short fiber was used and the heat treatment temperature by the heat treatment machine 18 was set to 170 ° C.

Comparative Example 6
A composite short fiber was obtained in the same manner as in Example 32 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape shown in FIG.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 32.

Example 33
Nylon 66 having a melting point of 257 ° C. and a relative viscosity of 2.50 is used as the polymer A, and a polyethylene having a melting point of 132 ° C. and a melt index (MI) value of 20 g / min is used as the polymer B. Used, melt spinning was carried out under the conditions of a spinning temperature of 285 ° C., a discharge rate of 448 g / min (nylon 336 g / min, polyethylene 112 g / min) and a spinning speed of 700 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 1014 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.4 ktex tow and then drawn at a draw ratio of 4.18 times and a draw temperature of 55 ° C. Subsequently, crimping was applied using a push-in crimper, with the crimping conditions set to a nip pressure of 0.55 MPa and a stuffing pressure of 0.24 MPa. Thereafter, an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil agent was applied so that the adhesion amount was 0.2% by mass, and then cut to be a composite short fiber having a single yarn fineness of 17.0 dtex and a fiber length of 5 mm. Got.
Next, a dry nonwoven fabric was obtained in the same manner as in Example 18 using the obtained composite short fiber.

Comparative Example 7
A composite short fiber was obtained in the same manner as in Example 33 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape shown in FIG.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 33.

Example 34
Nylon 66 having a melting point of 257 ° C. and a relative viscosity of 2.50 is used as the polymer A, and a polypropylene having a melting point of 163 ° C. and a melt index (MI) value of 28 g / min is used as the polymer B. Used, melt spinning was carried out under the conditions of a spinning temperature of 285 ° C., a discharge rate of 460 g / min (nylon 345 g / min, polypropylene 115 g / min) and a spinning speed of 700 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having a number of spinning holes of 1014), and an undrawn yarn was obtained. After focusing on an 8 ktex tow, stretching was performed at a stretching ratio of 4.30 times and a stretching temperature of 55 ° C. Subsequently, crimping was performed with a push-in crimper, with the crimping conditions set to a nip pressure of 0.56 MPa and a stuffing pressure of 0.25 MPa. Thereafter, an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil agent was applied so that the adhesion amount was 0.2% by mass, and then cut to be a composite short fiber having a single yarn fineness of 17.0 dtex and a fiber length of 5 mm. Got.
Next, a dry nonwoven fabric was obtained in the same manner as in Example 18 except that the obtained composite short fiber was used and the heat treatment temperature by the heat treatment machine 18 was set to 170 ° C.

Comparative Example 8
A composite short fiber was obtained in the same manner as in Example 34 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape shown in FIG.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 34.

Examples 35-36, Comparative Examples 9-10
A composite short fiber was obtained in the same manner as in Example 1 except that the fiber length at the time of cutting was changed to the fiber length shown in Table 1, and a dry nonwoven fabric was obtained in the same manner as in Example 1.

Comparative Example 11
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.53 is used as polymer A, and polyethylene having a melting point of 132 ° C. and a melt index (MI) value of 20 g / min is used as polymer B. Used, melt spinning was performed under the conditions of a spinning temperature of 280 ° C., a discharge rate of 252 g / min (nylon 189 g / min, polyethylene 63 g / min) and a spinning speed of 1200 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 2000 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 11.8 ktex tow and then drawn at a draw ratio of 2.63 times and a draw temperature of 50 ° C. Subsequently, crimping was performed with a push-in type crimper with the nip pressure of 0.33 MPa and the stuffing pressure of 0.11 MPa. Then, after applying an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil so as to have an adhesion amount of 0.2% by mass, the composite short fiber having a single yarn fineness of 0.4 dtex and a fiber length of 5 mm is cut. Obtained.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Comparative Example 12
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.53 is used as polymer A, and polyethylene having a melting point of 132 ° C. and a melt index (MI) value of 20 g / min is used as polymer B. The melt spinning was performed under the conditions of a spinning temperature of 270 ° C., a discharge rate of 520 g / min (nylon 390 g / min, polyethylene 130 g / min), and a spinning speed of 600 m / min. At this time, composite spinning was performed so as to obtain a fiber having a cross-sectional shape as shown in FIG. 1 (using a spinneret having 90 spinning holes) to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.4 ktex tow and then drawn at a draw ratio of 4.38 times and a draw temperature of 55 ° C. Subsequently, the crimping condition was applied by a push-in type crimper with the nip pressure of 0.60 MPa and the stuffing pressure of 0.30 MPa. Thereafter, an oil agent containing polyoxyethylene alkyl ether as a main component as a finishing oil agent was applied so that the adhesion amount was 0.2% by mass, and then cut into a composite short fiber having a single yarn fineness of 22.0 dtex and a fiber length of 5 mm. Got.
Next, using the obtained composite short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Reference example 1
Nylon 6 having a melting point of 216 ° C. and a relative viscosity of 2.52 was melt-spun using a normal melt spinning apparatus at a spinning temperature of 270 ° C., a discharge rate of 404 g / min, and a spinning speed of 1000 m / min. At this time, an undrawn yarn was obtained by using a spinneret having 518 spinning holes so as to have a round cross-sectional shape. The resulting undrawn yarn was focused on a 12.3 ktex tow and then drawn at a draw ratio of 3.55 and a draw temperature of 50 ° C. Subsequently, crimping was performed with a push-in type crimper with the nip pressure of 0.43 MPa and the stuffing pressure of 0.15 MPa. Thereafter, an oil agent mainly composed of polyoxyethylene alkyl ether as a finishing oil agent was applied so as to have an adhesion amount of 0.2% by mass, and then cut into short fibers having a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Obtained.

  Table 1 shows measured values and evaluation results of the composite short fibers obtained in Examples 1 to 36 and Comparative Examples 1 to 12. Table 1 shows the evaluation results of the uniformity, air permeability, and flexibility of the dry nonwoven fabric using these composite short fibers.

  As is apparent from Table 1, the composite short fibers of Examples 1 to 36 have an air agitation division ratio of 65% or more, among which Examples 1 to 8, 15 to 25, and 32 to 36 are (1) Since the expression (3) was satisfied, the air stirring division ratio was particularly high, 75% or more, and it was easily divided into ultrafine fibers. For this reason, the obtained nonwoven fabric was excellent in uniformity, air permeability, and flexibility.

  On the other hand, in the composite short fibers of Comparative Examples 1 to 8, in the cross section cut perpendicular to the longitudinal direction of the fibers, since the polymers A and B were arranged radially, the air stirring division ratio was low. there were. For this reason, the nonwoven fabric obtained from these short fibers has high air permeability and poor flexibility.

  In addition, the composite short fiber of Comparative Example 9 was too short in fiber length, so that the fibers were adhered due to frictional heat at the time of fiber cutting, hardly opened by preliminary opening, and a nonwoven fabric could not be obtained. . Since the composite short fiber of Comparative Example 10 was too long, it was easy to accumulate static electricity, and entanglement of the fiber was generated, forming a ball-like fiber lump, and the air stirring division ratio was low. For this reason, the obtained dry nonwoven fabric was inferior in uniformity, high air permeability, and poor flexibility. The composite short fiber of Comparative Example 11 had a single yarn fineness that was too small, so that a cut yarn was generated during spinning and the spinning operability was poor. Further, the fibers were closely adhered by the cut yarn, and the air stirring division ratio was low. For this reason, the obtained dry nonwoven fabric was inferior in uniformity, high air permeability, and poor in flexibility. Since the composite short fiber of Comparative Example 12 had a single yarn fineness that was too large, the fineness of the fiber after splitting was not sufficiently reduced, and ultrafine fibers could not be obtained. The resulting dry nonwoven fabric had high air permeability. It was inflexible.

Examples 37 to 39, Comparative Example 13
Using the split composite short fiber of Example 1 and the short fiber of Reference Example 1 shown above as the other fiber, the mass ratio (split composite short fiber of Example 1 / short fiber of Reference Example 1) Various changes were made as shown in Table 2, and both fibers were put into a simple air flow agitation tester shown in FIG. 7 to obtain a dry nonwoven fabric in the same manner as in Example 1. At this time, the main fibers constituting the nonwoven fabric were the short fibers made of the polymer A (polyamide short fibers) and the short fibers of Reference Example 1.

Examples 40 to 42, Comparative Example 14
Using the split composite short fiber of Example 18 and the short fiber of Reference Example 1 shown above as the other fiber, the mass ratio (split composite short fiber of Example 18 / short fiber of Reference Example 1) is shown. Various changes were made as shown in Fig. 2, and both fibers were put into a simple air flow agitating tester shown in Fig. 7 to obtain a dry nonwoven fabric in the same manner as in Example 18. At this time, the main fibers constituting the nonwoven fabric were the short fibers made of the polymer A (polyamide short fibers) and the short fibers of Reference Example 1.

  Table 2 shows the evaluation results of the uniformity, air permeability, and flexibility of the dry nonwoven fabrics obtained in Examples 37 to 42 and Comparative Examples 13 to 14.

  As is clear from Table 2, the short fiber nonwoven fabrics (dry nonwoven fabrics) of Examples 37 to 42 contain 30% by mass or more of polyamide short fibers divided from the composite short fibers of the present invention, and are uniform. It was excellent in properties, air permeability, and flexibility.

  On the other hand, since the short fiber nonwoven fabrics of Comparative Examples 13 to 14 did not contain 30% by mass or more of the polyamide short fibers divided from the composite short fibers of the present invention, the air permeability was high and the flexibility was poor. .

It is a cross-sectional view which shows one embodiment of the split-type composite short fiber of this invention. It is a cross-sectional view which shows the other embodiment of the split-type composite short fiber of this invention. It is a cross-sectional view which shows the other embodiment of the split-type composite short fiber of this invention. It is a cross-sectional view showing one embodiment of a split type composite short fiber in which two types of polymers are arranged radially. It is a schematic diagram which shows the state which the division | segmentation type | mold composite staple fiber of FIG. 1 divided | segmented. It is an expansion explanatory view showing the crimped form of the split type composite short fiber of the present invention. It is explanatory drawing which shows the simple airflow stirring test machine used when measuring, calculating, the test of a fiber lump, and manufacturing a dry nonwoven fabric of the air stirring division ratio of this invention. It is explanatory drawing which shows an example of the simple airlaid tester used when manufacturing the dry type nonwoven fabric by the airlaid method among the short fiber nonwoven fabrics of this invention.

Claims (6)

A split type composite fiber consisting of two components, a polyamide polymer A and a polyolefin polymer B, which is used to obtain a dry nonwoven fabric by the airlaid method and cut perpendicular to the longitudinal direction of the fiber In the cross section, it has a shape in which a plurality of polyamide polymers are arranged in contact with the periphery of the polyolefin polymer (except that the cross-sectional shape of the composite fiber is a circular cross section) , and the air stirring division rate is a but 65% or more, the fiber length is 1.0～30Mm, single yarn fineness of Ri 0.5~20dtex der, the fibers, crimping has been granted, the maximum peak of the crimp form of single yarn crimp portion The ratio (H / L) of the height (H) and base (L) of the triangle connecting the top of the peak and the bottom of the valley adjacent to the peak satisfies the following formula (1) Characteristic split composite short fiber.
(1) Formula: 0.01T + 0.10 ≦ H / L ≦ 0.02T + 0.25
T is the number of decitex (dtex) of single yarn fineness The split-type composite short fiber according to claim 1 , wherein the number of crimps and the crimp rate satisfy the following expressions (2) and (3) simultaneously.
(2) Formula: 0.1T + 3.8 ≦ crimp number ≦ 0.3T + 7.3
(3) Formula: 0.8T + 0.3 ≦ crimp rate ≦ 1.0T + 4.9
However, the number of crimps is the number per 25 mm of fiber length, and T is the number of decitex (dtex) of single yarn fineness. The split type composite short fiber according to claim 1 or 2 , wherein the polyamide polymer has a melting point of 200 ° C or higher. A method for producing a short-fiber nonwoven fabric, comprising using the split-type composite short fibers according to any one of claims 1 to 3 to produce a web by an airlaid method to obtain a nonwoven fabric. 5. The method for producing a short fiber nonwoven fabric according to claim 4, wherein the split type composite fiber is divided by an air flow in the air laid method when the web is formed by the air laid method. A short fiber nonwoven fabric obtained by the method for producing a short fiber nonwoven fabric according to claim 4 or 5.