JP4791156B2 - Split composite short fiber and short fiber nonwoven fabric - Google Patents

Description

The present invention relates to a splittable conjugate fiber comprising two components of the polyester polymer and the polyolefin polymer, a high division ratios of both components has excellent split resistance, to dry the nonwoven fabric according to air-laid process Ru der relates splittable composite short fibers used.

  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, a polyester polymer mainly composed of a polyalkylene terephthalate unit and a polyolefin polymer, the fiber for obtaining a dry nonwoven fabric by the airlaid method, In the cross section cut perpendicularly to the longitudinal direction, a plurality of polyester polymers are arranged in contact with the periphery of the polyolefin polymer (however, the cross-sectional shape of the composite fiber is a circular cross section) excluding.), and the air agitation 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, the single yarn wound The ratio (H / L) of the height (H) to the base (L) of the triangle connecting the two peak points of the valleys adjacent to the peak of the peak at the maximum peak of the crimped part is as follows. (1) divided form characterized by satisfying the equation If short fibers.
(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).

  The split-type composite short fiber of the present invention has a high split ratio by air agitation and can be easily split into ultrafine fibers. Therefore, the split-type composite short fiber can be suitably used particularly in the production of a dry nonwoven fabric in which a fiber lump is easily generated due to generation of static electricity. It is possible to obtain a non-woven fabric made of ultrafine fibers with few undivided parts, excellent uniformity, soft texture, and low air permeability. Moreover, since the short fiber nonwoven fabric of the present invention contains ultrafine fibers divided from the split composite short fibers of the present invention, it is a nonwoven fabric having uniformity and soft texture, low air permeability, It can be used for various purposes.

  Hereinafter, the present invention will be described in detail.

The split-type composite short fibers of the present invention (hereinafter abbreviated as composite short fibers) are a polyester-based polymer (referred to as polymer A) mainly composed of polyalkylene terephthalate units and a polyolefin-based polymer (referred to as polymer B). ) In a cross section cut perpendicularly to the longitudinal direction of the fiber, and a shape in which a plurality of polymers A are arranged in contact with the periphery of the polymer B (however, the cross section of the composite fiber) Excluding those with 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 is measured based on the JIS L1015 8.4.1A method, and the single yarn fineness is measured based on the JIS L1015 8.5.1B method.

  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 splitting ratio 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 part made of the polymer A and a part 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 divided | segmented from the composite fiber in 10 photographed images is counted, and it calculates with the following formula from the number of arrangement | sequences of the polymer A before division | segmentation.

Air stirring division ratio (%) = (number of divided polymers A / number of arrays 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

  Since the air agitation division ratio is 65% or more, it is easily divided into ultrafine fibers by air agitation. Therefore, not only when producing a dry nonwoven fabric by the airlaid method, but also when producing a wet nonwoven fabric, It is possible to obtain a non-woven fabric having a small number of divided portions, excellent uniformity, low air permeability, and soft texture. 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 is provided with crimps , and the crimped form of the single yarn is the bottom point 2 of the valley part adjacent to the apex of the peak part at the maximum peak part of the crimped part. The ratio (H / L) between the height (H) of the triangle connecting the points and the base (L) 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, the obtained nonwoven fabric tends to have poor 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 number of crimps is measured and calculated based on JIS L1015 8.12.1. 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 in the air flow. 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. Moreover, the obtained nonwoven fabric has 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]. This crimp rate is measured and calculated based on JIS L1015 8.12.2. 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. Moreover, the obtained nonwoven fabric has poor uniformity.

  Next, the polyester-based polymer mainly composed of the polyalkylene terephthalate unit constituting the composite short fiber of the present invention preferably has a melting point of 220 ° C. or higher in order to stably produce the fiber. Is preferably 220 to 280 ° C. Specific examples include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Among these, PET is preferable. If necessary, a copolymerized polyester obtained by copolymerizing one or more of the following copolymerization components may be used.

  Copolymerization components include terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, bisphenol A, bisphenol S, cyclohexanedimethanol, 1,4-butanediol, 1,6-hexadiol, diethylene glycol, polyethylene glycol Etc.

  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. A copolymerized olefin may be used as necessary.

  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, fibers are divided when transported into the fiber production machine (preliminary defibration or air feeding) or defibrated, and there is no need to separately provide a process and equipment for dividing the fibers, which is advantageous in terms of cost. is there.

  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 obtain a non-woven fabric by using a polyester-based polymer after splitting as a main fiber and a polyolefin-based polymer as a binder fiber, and performing heat treatment to melt the binder fiber portion made of the polyolefin-based polymer.

  When the nonwoven fabric is made using only the short fiber of the present invention as described above, the binder fiber (polyolefin polymer) can be easily melted and bonded to the main fiber only by heat treatment with hot air. Thus, the bonding step using a binder resin or the pressure bonding step using a hot roll can be omitted, 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, and the fiber length made of a polyester polymer mainly composed of polyalkylene terephthalate units is 1.0 to 30 mm. The polyester staple fiber having a single yarn fineness of 0.05 to 5 dtex is contained by 40% by mass or more.

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 polyester fiber is a main fiber and the polyolefin polymer is a binder fiber, and the binder fiber is melted. Those obtained by bonding the main fibers are preferable.

    The mass of the polyester short fiber comprising the polyester polymer in the nonwoven fabric is preferably 30% by mass or more, and more preferably 40% by mass or more. If the amount is less than 30% by mass, the resulting nonwoven fabric has a low proportion of ultrafine fibers, so that it 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, other short fibers may be used together with the composite short fiber of the present invention as long as the mass of the polyester short fiber composed of the polyester polymer in the nonwoven fabric is 30% by mass or more. In this case, other short fibers may be used for either the main fiber or the 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 polyester polymer and a polyolefin polymer are combined and spun using a commonly used compound spinning apparatus. 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. The falling short fibers are sucked by the suction box 14 at the lower part and deposited on the cotton collecting conveyor 17 that moves in the direction of the arrow to create a web, and heat treated by the heat treatment machine 18 downstream (heat treatment temperature: olefin). To obtain a dry nonwoven fabric. 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) Intrinsic viscosity Measured at a temperature of 20 ° C. using a mixture of equal mass of phenol and ethane tetrachloride 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-Uniformity-
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 the fineness before division is 2.2 T: 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 17T: ○: 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
A PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is used as the polymer A, a polyethylene having a melting point of 131 ° C. and a melt index (MI) value of 20 g / min is used as the polymer B, and these are used in an ordinary composite melt spinning apparatus. The melt spinning was performed under the conditions of a spinning temperature of 278 ° C., a discharge amount of 568 g / min (PET 426 g / min, polyethylene 142 g / min), and a spinning speed of 1000 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 to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.3 ktex tow and then drawn at a draw ratio of 2.55 times and a draw temperature of 75 ° C. Subsequently, crimping was applied with a push-in type crimper with the nip pressure of 0.38 MPa and the stuffing pressure of 0.10 MPa. Then, after applying a commonly used spinning oil mainly composed of polyoxyethylene alkyl ether as a finishing oil so as to have an adhesion amount of 0.2% by mass, it was cut to a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. The composite short fiber was obtained.
Using the simple air flow agitation tester shown in FIG. 7, only the composite short fiber of the present invention 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. Blow and stir 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, the composite short fiber of the present invention that has been pre-opened from the sample input blower 13 is input and rotated by the disentanglement blade rotation motor 15 via the disentanglement blade rotation sprocket 16. The fiber was defibrated with the defibrating blade 12 and dropped. The falling short fibers are sucked by the suction box 14 at the lower part and deposited on the cotton collecting conveyor 17 that moves in the direction of the arrow to create a web, and then heat treated by the heat treatment machine 18 downstream (heat treatment temperature: 140). The polymer B was melted by applying (C), and a dry nonwoven fabric mainly comprising polyester short fibers made of the polymer A was obtained. 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, the composite short fiber was obtained in the same manner as in Example 1 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape of FIGS. In the same manner as in Example 1, a dry nonwoven fabric was obtained.

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. Further, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Example 15
A PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is used as a 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 a polymer B. The melt spinning was performed under the conditions of a spinning temperature of 282 ° C., a discharge rate of 608 g / min (PET 456 g / min, polypropylene 152 g / min), and a spinning speed of 1000 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 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 2.73 times and a draw temperature of 75 ° C. Subsequently, the crimping condition was applied by a push-in crimper with a nip pressure of 0.40 MPa and a stuffing pressure of 0.10 MPa. Thereafter, a commonly used spinning oil mainly composed of polyoxyethylene alkyl ether as a finishing oil was applied so that the adhesion amount was 0.2% by mass, and then cut to obtain a single yarn fineness of 2.2 dtex and a fiber length. A 5 mm composite short fiber was obtained.
Next, a dry nonwoven fabric was obtained using the obtained composite short fibers in the same manner as in Example 1. However, the heat treatment temperature at which the polymer B was melted after creating the web was 170 ° C.

Comparative Example 2
Except for changing the spinneret so that the cross-sectional shape of the fiber becomes the shape shown in FIG. 4, a composite short fiber was obtained in the same manner as in Example 15, and a dry nonwoven fabric was obtained in the same manner as in Example 15. .

Example 16
A PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is used as the polymer A, a polyethylene having a melting point of 131 ° C. and a melt index (MI) value of 20 g / min is used as the polymer B, and these are used in an ordinary composite melt spinning apparatus. The melt spinning was performed under the conditions of a spinning temperature of 278 ° C., a discharge rate of 452 g / min (PET 339 g / min, polyethylene 113 g / min), and a spinning speed of 900 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 to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.8 ktex tow, then drawn at a draw ratio of 3.28 times and a draw temperature of 75 ° C., and a crimping condition was applied by a push-in crimper with a nip pressure of 0.48 MPa and a stuffing pressure. Crimping was given as 0.17 MPa. Then, after applying a commonly used spinning oil mainly composed of polyoxyethylene alkyl ether as a finishing oil so as to have an adhesion amount of 0.2% by mass, it was cut to obtain a single yarn fineness of 17 dtex and a fiber length of 5 mm. A composite short fiber was obtained.
A dry nonwoven fabric was obtained in the same manner as Example 1 using the obtained composite short fiber.

Example 17, Comparative Example 3
As shown in Table 1, the composite short fiber was obtained in the same manner as in Example 16 except that the spinneret was changed so that the cross-sectional shape of the fiber became the shape of FIGS. In the same manner as in No. 16, a dry nonwoven fabric was obtained.

Examples 18-29
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 16. Further, a dry nonwoven fabric was obtained in the same manner as in Example 16.

Example 30
A PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is used as a 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 a polymer B. The melt spinning was performed under the conditions of a spinning temperature of 282 ° C., a discharge rate of 483 g / min (PET 362 g / min, polypropylene 121 g / min) and a spinning speed of 900 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 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 3.50 times and a draw temperature of 80 ° C. Subsequently, the crimping condition was applied by a push-in crimper with a nip pressure of 0.49 MPa and a stuffing pressure of 0.17 MPa. Then, after applying a commonly used spinning oil mainly composed of polyoxyethylene alkyl ether as a finishing oil so as to have an adhesion amount of 0.2% by mass, it was cut to obtain a single yarn fineness of 17 dtex and a fiber length of 5 mm. A composite short fiber was obtained.
Next, a dry nonwoven fabric was obtained using the obtained composite short fibers in the same manner as in Example 1. However, the heat treatment temperature at which the polymer B was melted after creating the web was 170 ° C.

Comparative Example 4
Except for changing the spinneret so that the cross-sectional shape of the fiber becomes the shape shown in FIG. 4, a composite short fiber was obtained in the same manner as in Example 30, and a dry nonwoven fabric was obtained in the same manner as in Example 30. .

Examples 31-32, Comparative Examples 5-6
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.

  Table 1 shows measured values and evaluation results of the composite short fibers obtained in Examples 1 to 32 and Comparative Examples 1 to 6. Table 1 shows the evaluation results of the uniformity, air permeability, and flexibility of the dry nonwoven fabric made of these short fibers.

  As is apparent from Table 1, the composite short fibers of Examples 1 to 32 have an air agitation division ratio of 65% or more. Among them, Examples 1 to 8, 15 to 23, and 30 to 32 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 4, the polymers A and B were arranged radially in the cross section cut perpendicular to the longitudinal direction of the fibers, and thus 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.

  Further, the composite short fiber of Comparative Example 5 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 6 was too long, it was easy to accumulate static electricity, entangled fibers, formed a ball-shaped fiber lump, and had a low air stirring division rate. For this reason, the obtained dry nonwoven fabric was inferior in uniformity, high air permeability, and poor flexibility.

Examples 33 to 35, Comparative Example 7
Using the split composite short fiber of Example 1 and the short fiber of Reference Example 1 shown below as the other fiber, the mass ratio (split composite short fiber of Example 1 / short fiber of Reference Example 1) is 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 and the short fibers of Reference Example 1.

Reference example 1
As polyester, a PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is formed using a normal melt spinning apparatus, with a spinning temperature of 285 ° C., a discharge rate of 344 g / min, and a spinning speed of 950 m / min. Spinning was performed with a nozzle having a mold section to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 12.3 ktex tow, then drawn at a draw ratio of 3.18 times and a draw temperature of 70 ° C., and a crimping condition was applied by a push-in crimper with a nip pressure of 0.32 MPa and a stuffing pressure. Crimping was applied as 0.09 MPa. Then, after applying a spinning oil 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 to a short fiber having a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Got.

Examples 36 to 38, Comparative Example 8
Table 2 shows the mass ratio of the split composite short fibers of Example 16 and the short fibers of Reference Example 1 as the other fibers, and the mass ratio (split composite short fibers of Example 1 / short fibers of Reference Example 1). Various changes were made as described above, and both fibers were put into a simple air flow agitating tester shown in FIG. 7, and a dry nonwoven fabric was obtained in the same manner as in Example 16. At this time, the main fibers constituting the nonwoven fabric were the short fibers made of the polymer A 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 33 to 38 and Comparative Examples 7 to 8.

  As can be seen from Table 2, the short fiber nonwoven fabrics (dry nonwoven fabrics) of Examples 33 to 38 contained 30% by mass or more of the fibers of the present invention, and thus were uniform, air permeable, and flexible. It was excellent.

  On the other hand, since the short fiber nonwoven fabrics of Comparative Examples 7 to 8 did not contain 30% by mass or more of the fiber 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 expanded explanatory view which shows the crimped form of the short fiber for nonwoven fabrics of this invention. It is explanatory drawing which shows the simple airflow stirring tester used when performing preliminary opening when measuring and calculating 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 comprising two components of a polyester polymer and a polyolefin polymer mainly composed of a polyalkylene terephthalate unit, the fiber for obtaining a dry nonwoven fabric by an airlaid method, and the longitudinal direction of the fiber In the cross section cut perpendicularly to the surface, a plurality of polyester polymers are arranged in contact with the periphery of the polyolefin polymer (however, the cross-sectional shape of the composite fiber is not circular. ), and the air agitation 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 At the maximum peak of the crimped part, the ratio (H / L) of the height (H) to the base (L) of the triangle connecting the top of the peak and the bottom of the adjacent valley is (1) splittable composite short, characterized by satisfying the equation Wei.
(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 melting point of the polyester polymer is 220 ° 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.