JP2006193838A - Staple fiber for nonwoven fabric and staple fiber nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide staple fibers which are used for nonwoven fabric, can prevent the formation of fiber masses by the generation of static electricity by frictions between the fibers-fibers and between the fibers-machines especially in a process for producing a dry nonwoven fabric without imparting a special treating agent to the surfaces of the fibers, and can give the nonwoven fabric having excellent uniformity, high quality and sufficient bulkiness. <P>SOLUTION: The crimped staple fibers for the nonwoven fabric, comprising a polyester consisting mainly of alkylene terephthalate units, and having a fiber length of 1.0 to 30 mm, a single fiber fineness of 1.0 to 40 dtex, a birefringence of ≤0.0150, and an elongation of ≥250%, is characterized in that the height (H) to the bottom (L) (H/L) of a triangle formed by binding the mountain tip to two bottom points in the adjacent valleys at the largest mountain portion of a crimped portion in the crimped shape of a single fiber satisfies the following expression (1) : 0.01T+0.1≤H/L≤0.02T+0.25, wherein T is the decitex (dtex) of single fiber fineness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a polyester short fiber used for a nonwoven fabric such as a dry nonwoven fabric or a wet nonwoven fabric, and is a web for feeding, dispersing, defibrating, laminating process, etc. of a short fiber by an air flow, a card machine or the like in the nonwoven fabric manufacturing process. The present invention relates to a short fiber for a nonwoven fabric provided with an appropriate crimped form in which a fiber lump is not formed in the forming step, and a short fiber nonwoven fabric containing the short fiber.

  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 and wet nonwoven fabrics obtained by water flow or entanglement with metal needles are used.

  In the case of obtaining a dry nonwoven fabric using such short fibers, especially in the airlaid method, the fibers are defibrated and transported in a flow of air, passed through a screen having a wire mesh or pores, and then on a wire mesh. However, in the process of defibrating, transporting, dispersing, and laminating short fibers, the friction between fibers and fibers and fibers and metals is large, and static electricity is easily generated. The problem of being apt to occur.

  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 for product differentiation, upgrading, and high functionality. Some of them require low-temperature processing, high-viscosity thermoplastic resins, etc. As compared with the conventional fiber, a fiber having a greater fiber-fiber friction and fiber-metal friction is used. In addition, 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.

  In order to solve such problems, it is effective to apply a fiber treatment agent having antistatic properties and smoothness to the fiber surface. As finishing oil agents that impart smoothness and antistatic properties, fats mainly composed of waxes or fatty acids, and quaternary ammonium salts containing long-chain alkyl groups are widely used. However, although these fats can impart antistatic properties to some extent, they cannot impart sufficient smoothness.

On the other hand, silicone finishing oils are known as fiber finishing oils having excellent smoothness. For example, fibers and fiber cords to which dimethylsiloxane emulsion polymer, amine-modified silicone and the like are added have been proposed (for example, patents). (See Reference 1.)
However, both the dimethylsiloxane emulsion polymer and the amine-modified silicone have insufficient antistatic properties, and further, there is a problem that the hydrophilicity is inhibited and the fiber and the obtained product are yellowed. Moreover, these are not short fibers but long fibers (fiber cords), and cannot solve the problems caused by the generation of static electricity in the manufacturing process of the nonwoven fabric.

Further, as a fiber imparted with smoothness, antistatic property and hydrophilicity, a highly smooth fiber imparted with a mixture of an alkyl phosphate salt and an amide group-containing polyoxyalkylene-modified silicone composition has been proposed. (For example, see Patent Document 2.)
However, since this fiber also has smoothness and antistatic properties by applying a special treatment agent, there is a problem that it is disadvantageous in terms of operability and cost. In addition, there are various needs for the obtained nonwoven fabric, and various treatments are performed for the purpose of imparting high functionality to the nonwoven fabric, so that the resulting nonwoven fabric may be discolored or colored by the treatment agent applied to the fibers. There were problems and quality was insufficient.
Japanese Patent Publication No. 48-1480 Japanese Patent Laid-Open No. 9-67772

  The present invention solves the above problems and generates static electricity due to friction between fibers and fibers or between fibers and machines, particularly in the production process of a dry nonwoven fabric, without applying a special treatment agent to the fiber surface. The short fiber for a nonwoven fabric and the short fiber nonwoven fabric containing the short fiber, which can prevent the generation of fiber mass due to the above, can obtain a nonwoven fabric excellent in uniformity, high quality and sufficient bulkiness It is a technical challenge to provide

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) and (b).
(A) Made of polyester mainly composed of alkylene terephthalate unit, fiber length is 1.0-30mm, single yarn fineness is 1.0-40dtex, birefringence is 0.0150 or less, elongation is 250% or more, and crimp is given The height of the triangles (H) and the bases of the short fibers that are connected to the peak of the peak and the bottom of the valley adjacent to the peak at the maximum peak of the crimp. A short fiber for nonwoven fabric, wherein the ratio (H / L) of L) satisfies the following formula (1):
(1) Formula: 0.01T + 0.1 ≦ H / L ≦ 0.02T + 0.25
T is a short fiber nonwoven fabric characterized by containing 10% by mass or more of the short fibers for nonwoven fabric described in the number of detex (dtex) of single yarn fineness (a) (a).

  Since the short fiber for nonwoven fabric of the present invention satisfies a specific crimped form, it does not give a special treatment agent to the fiber surface, and is caused by generation of static electricity due to friction between fibers and fibers and between fibers and machines. It is possible to prevent the generation of fiber clumps, and furthermore, it is possible to prevent the static electricity between the fibers (for) and to prevent the entanglement of the fibers. Therefore, it has excellent uniformity, high quality, bulkiness, and flexibility. It is possible to obtain a sufficient nonwoven fabric (dry nonwoven fabric and wet nonwoven fabric). The short fiber for nonwoven fabric according to the present invention has a specific birefringence and elongation, so that at least a part of the fiber melts at a heat treatment temperature lower than the melting point of the polyester forming the fiber. It becomes a binder fiber that melts at a low heat treatment temperature. For this reason, it becomes possible to obtain a non-woven fabric having a good texture without causing deterioration of the polymer or curing of the texture.

  Moreover, since the short fiber nonwoven fabric of the present invention comprises the short fiber for nonwoven fabric of the present invention, both the dry nonwoven fabric and the wet nonwoven fabric have excellent uniformity, high quality, bulkiness, flexibility, The texture is also a non-woven fabric that can be used for various purposes.

Hereinafter, the present invention will be described in detail.
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 in 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), since an air flow is actively generated, the fibers are rubbed with each other. The generation of static electricity also increases due to friction with the device (metal).

  The short fiber of the present invention generates static electricity by friction between fibers and between fiber and metal in all web forming processes (defibration, transport, dispersion, and lamination processes) by making the fiber structure specific. It is difficult to prevent static electricity generated and the short fibers gather to form a fiber lump.

  When considering the problem of static electricity as described above, there are many crimps. That is, if the fiber is crimped, it exhibits a three-dimensional structure, so that static electricity is more likely to accumulate as the three-dimensional space portion increases. On the other hand, the flatter the state without crimps, the more planar the structure becomes, and the more difficult it is to accumulate static electricity. However, the number of contact points (surfaces) between fibers or 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. Further, since a three-dimensional structure is formed by crimping, the single yarn fineness is a factor that affects the size of the space portion, and is a factor that affects the degree of static electricity and the degree of fiber entanglement.

  Therefore, the present inventors considered these factors in consideration and made the above-mentioned effect (static electricity, fiber entanglement) particularly by adopting a three-dimensional shape to which specific crimps were given in consideration of the single yarn fineness. And the improvement of the texture of the nonwoven fabric was found to be improved.

  First, the short fiber for nonwoven fabric of the present invention, as shown in FIG. 1, in the crimped form of a single yarn, the apex P of the peak in the maximum peak of the crimped part, and the bottom point Q of the adjacent valley, A triangle is formed by connecting two points R, and the ratio (H / L) of the height (H) to the base (L) of the triangle satisfies the following expression (1). In particular, when a dry nonwoven fabric is obtained by the air laid method, it is preferable that H / L is represented by the formula (4).

Here, when there are a plurality of peak portions in the fiber length of the short fiber of the present invention, the maximum peak portion means the one having the highest peak height (H).
(1) Formula: 0.01T + 0.1 ≦ H / L ≦ 0.02T + 0.25
(4) Formula: 0.01T + 0.1 ≦ H / L ≦ 0.02T + 0.20

  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. In the present invention, even if the expression (3) that defines the crimping rate described later is satisfied, if there is a part where the crimping is greatly applied to some of the crimped parts in the fiber, the space of the three-dimensional structure A part becomes large, it is easy to accumulate static electricity, and it becomes easy to produce the entanglement of fibers. Therefore, as specified in the formula (1), by making the form at the maximum peak part specific as the crimped form, it becomes possible to prevent the generation of fiber mass due to static electricity or fiber entanglement.

  When H / L is too large, the space portion of the three-dimensional structure becomes large, static electricity is easily accumulated, and fiber entanglement tends to occur. On the other hand, if H / L is too small, 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. It is not preferable. Moreover, the obtained nonwoven fabric tends to be poor in bulkiness.

  For the measurement of H / L, 1 g of short fibers are collected, and 20 single fibers are arbitrarily taken out 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 bottom points Q and R of the valley portion adjacent to the vertex P of the mountain portion at the maximum mountain portion are obtained. 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 short fiber of the present invention preferably satisfies the following formula (2): 0.1T + 3.8 ≦ crimp 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, in the measurement of the number of crimps, when the fiber length is short and measurement is difficult, the measurement is performed on the fibers before the crimping and before the cut, and converted into the number per 25 mm fiber length.

  If the number of crimps is higher than the formula (2), the number of crimped portions that become space portions due to a three-dimensional structure increases, and the short fibers are fed, dispersed, defibrated, and laminated between the fibers in the air flow. The generated static electricity is easily accumulated, and the 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. This is not preferable because a fiber-like fiber lump is formed. Moreover, the obtained nonwoven fabric tends to be poor in bulkiness.

  Furthermore, the short fiber for nonwoven fabric of the present invention preferably satisfies the following formula (3): 0.8T + 0.3 ≦ crimp rate ≦ 1.0T + 4.9 [T is the single yarn fineness (dtex)]. This crimp rate is measured and calculated based on JIS L1015 8.12.2. In addition, in the measurement of the number of crimps, when the fiber length is short and measurement is difficult, the measurement is performed on the fibers before the crimping and before the cut, and converted into the number per 25 mm fiber length.

  When the crimping rate is higher than that of equation (3), the space part due to the three-dimensional structure increases, and the static electricity generated between the fibers is reduced during the feeding, dispersion, defibration, and lamination processes of the short fibers in the air flow. Since it becomes easy and the fibers are easily entangled, a ball-shaped fiber lump is generated, 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. Is not preferable. Moreover, the obtained nonwoven fabric tends to be poor in bulkiness.

In terms of the number of crimps and the crimp rate, it is preferable that the crimp number satisfies the formula (5) and the crimp rate satisfies the formula (6), particularly when a dry nonwoven fabric is obtained by the airlaid method.
(5) Formula: 0.1T + 4.8 ≦ crimp number ≦ 0.2T + 6.6
(6) Formula: 0.8T + 1.2 ≦ crimp rate ≦ 1.0T + 2.8

  The short fiber of the present invention has a fiber length of 1.0 to 30 mm and a single yarn fineness of 1.0 to 40 dtex, and a more preferable fiber length is 2 to 25 mm, more preferably 5 to 15 mm. The single yarn fineness is preferably 1.3 to 33 dtex, more preferably 1.5 to 25 dtex. The fiber length was measured based on the JIS L1015 8.4.1A method, and the fineness was measured based on the JIS L1015 8.5.1B method.

  The short fiber of the present invention is made of polyester mainly composed of an alkylene terephthalate unit. In order to stably produce a fiber, among these, a polyester composed mainly of an alkylene terephthalate unit having a melting point of 220 ° C. or higher is preferable. Specific examples include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Among these, PET is preferable. Moreover, these polyesters are good also as the copolymer polyester which copolymerized the copolymerization component shown below as needed one type or multiple types.

  In addition, although it does not specifically limit as an upper limit of melting | fusing point, When setting it as the above polyesters, it is preferable to set it as 220-280 degreeC.

  Examples of the copolymer component include terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, bisphenol S, bisphenol A, cyclohexanedimethanol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, Examples include polyethylene glycol.

  Furthermore, in the polyester, in a range not impairing its effect, matting agents such as titanium oxide, antioxidants such as hindered phenol compounds, ultraviolet absorbers, light stabilizers, pigments, flame retardants, antibacterial agents, A conductivity-imparting agent, a hydrophilic agent, a water-absorbing agent and the like may be blended.

  The short fiber of the present invention has a birefringence of 0.0150 or less and an elongation of 250% or more. The short fiber of the present invention has such characteristics and is mainly used as a binder fiber. That is, when the birefringence is 0.0150 or less and the elongation is 250% or more, the degree of molecular orientation of the polymer is not sufficient, and the crystallinity is low. For this reason, by heat-treating at a temperature lower than the melting point of the polyester, at least a part of the fibers is melted and serves as a binder fiber.

  Among them, the short fiber of the present invention is preferably one in which at least a part of the fiber melts when heat-treated at a temperature lower by 50 ° C. than the melting point of the polyester, and further, at a temperature lower by 100 ° C. than the melting point of the polyester. It is preferable that at least a part of the fibers melt when heat-treated.

  That is, when the melting point of the polyester is 220 ° C., the short fiber of the present invention is preferably one in which at least a part of the fiber melts when heat-treated at a temperature of 170 ° C. (220-50). It is preferable that at least a part of the fiber is melted when heat-treated at a temperature of 220C.

  The heat treatment at this time in the present invention means that 1 g of the short fiber of the present invention is collected, spread on a stainless steel wire net, and heat-treated for 10 minutes with a box-type hot air drier. It is to confirm with.

  The birefringence of the short fiber of the present invention is preferably 0.0150 or less, more preferably 0.0120 to 0.0050. The birefringence indicates the degree of molecular orientation, but if this exceeds 0.0150, the molecular orientation has progressed, the elongation has become low, and even if heat treatment is performed at a temperature lower than the melting point of the polyester, Since some of the fibers do not melt, they cannot be used as binder fibers.

  The elongation of the short fiber of the present invention is preferably 250% or more, and more preferably 300 to 530%. If the elongation is less than 250%, the molecular orientation of the polymer is advanced by stretching, the birefringence increases, and even if heat treatment is performed at a temperature lower than the melting point of the polyester, a part of the fiber is melted. Therefore, it cannot be used as a binder fiber.

  The birefringence in the present invention is measured by an interference fringe measurement method using a combination of a polarizing microscope and a compensator. The elongation is measured according to the method of JIS L1015 8.7 tensile strength and elongation. In addition, when a fiber is short and cannot be measured, it measures by obtaining 20 mm or 10 mm fiber in the fiber before cutting.

  Thus, since the short fiber of the present invention is not obtained using a special polymer having a low melting point, melt spinning can be easily performed and the fiber can be obtained with good operability.

  And since a part of fiber melts at temperature lower than melting | fusing point of a polymer, it can be used as a binder fiber. Furthermore, by appropriately selecting the heat treatment temperature, the nonwoven fabric is made of only the short fibers of the present invention, only a part of the fibers is melted, and the short fibers of the present invention are used as both the main fiber and the binder fiber. You can also.

  In the short fiber of the present invention, in order to satisfy the above-described crimped form, birefringence, and elongation of the single yarn, after the melt spinning, the undrawn yarn is not substantially stretched. It is preferable that it is what was obtained by providing. That is, after melt spinning, the crimping conditions (nip pressure, stuffing pressure) are adjusted to an appropriate value using a crimping device such as an indentation type crimper for the undrawn yarn obtained without substantially drawing. It is preferable to impart mechanical crimping.

  The short fibers of the present invention are suitable as short fibers for dry nonwoven fabrics and wet nonwoven fabrics, and the dry fibers are particularly suitable as short fibers for nonwoven fabrics manufactured by the airlaid method. According to the airlaid method, it is possible to easily obtain a non-woven fabric only by bonding with hot air, and it is possible to omit a bonding process using a binder resin or a pressure bonding process using a hot roll, which is advantageous in terms of cost.

  Furthermore, the short fiber of this invention can be used suitably also for manufacture of a wet nonwoven fabric. As described above, the short fiber of the present invention can prevent the generation of fiber mass due to the generation of static electricity due to the friction between fiber and fiber or between fiber and machine, particularly in the production process of dry nonwoven fabric. Even in wet nonwoven fabrics, the dispersion of single fibers is good, and since there are few contact points (surfaces) between single fibers, it is difficult for fibers to converge, and it is possible to obtain wet nonwoven fabrics with excellent uniformity and sufficient bulkiness it can.

  In addition, the cross-sectional shape of the short fiber of the present invention is not particularly limited, and is not limited to a round shape, but is a flat shape, a trilobal shape, a hexaloval shape, a W shape, an H shape, or other irregular cross sections, or a polygon such as a rectangle or a triangle. A shape or a hollow shape may be used.

Next, the short fiber nonwoven fabric of the present invention will be described. The short fiber nonwoven fabric of the present invention contains 10% by mass or more of the short fiber for nonwoven fabric of the present invention as described above. And it is preferable to use the short fiber of this invention as a binder fiber as above-mentioned. Specifically, the short fiber of the present invention melts at least a part of the fiber at a temperature lower than the melting point of the polyester, so that it becomes a binder fiber, and the part of the fiber remains without being melted. Becomes a main fiber constituting the nonwoven fabric.
Thereby, the nonwoven fabric which has the unique texture excellent in uniformity, bulkiness, and a softness | flexibility can be obtained.

  That is, the short fiber for nonwoven fabric of the present invention has a crimped shape as described above, thereby preventing the fibers from being entangled and producing a uniform and bulky web in the nonwoven fabric manufacturing process. In the case of the binder fiber, at least a part of the fiber is melted by the heat treatment, but since the main fiber and the short fiber of the present invention are uniform and bulky at the stage of the web, the short fiber of the present invention Even if a part of them melts, the nonwoven fabric satisfies the uniformity and bulkiness. And when all the short fibers of the present invention are melted, there is no remaining portion as the fibers, and it becomes possible to bond the main fibers with the melted components while maintaining the uniformity and bulkiness of the non-woven fabric. This will also improve the performance.

  In the nonwoven fabric of the present invention, when the proportion of the short fiber of the present invention is less than 10% by mass, the amount of the component that the short fiber melts becomes too small, so that the adhesive component is small and the bonding point of the main fiber is small. It tends to be difficult to make a nonwoven fabric. Even if it is obtained, it becomes a nonwoven fabric with poor mechanical properties.

  On the other hand, as described above, by selecting the heat treatment temperature, only a part of the short fiber of the present invention is melted, and when the short fiber of the present invention is used as both the binder fiber and the main fiber, the nonwoven fabric of the present invention is used. The ratio of the short fibers of the present invention may be 100% by mass. However, when all of the short fibers of the present invention are melted and used as a total melt binder fiber, the proportion of the short fibers of the present invention is preferably 60% by mass or less. When the ratio of the short fiber of the present invention exceeds 60% by mass, the ratio of the main fiber decreases, the bulkiness becomes poor, and the amount of the component in which the short fiber of the present invention melts increases so that the flexibility is increased. It tends to be a poor nonwoven fabric.

  The main fibers other than the short fibers of the present invention used in the nonwoven fabric of the present invention are the same as the short fibers of the present invention in view of the texture such as uniformity and bulkiness of the obtained nonwoven fabric. Therefore, it is preferable to use a short fiber that satisfies the shape, the number of crimps, and the crimp rate of the formulas (1) to (3) in the present invention.

  As such a main fiber, a synthetic fiber made of a thermoplastic resin made of polyester, polyamide, or the like can be used. Among them, a polyester mainly having an alkylene terephthalate unit, and the melting point of the polyester is 220 to 280. C. is preferred. Specific examples include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Among these, PET is preferable. Further, these polyesters may be copolymer polyesters obtained by copolymerizing one or more of the following copolymer components as required.

  Examples of copolymer components include terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, bisphenol S, bisphenol A, cyclohexanedimethanol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, Examples include polyethylene glycol.

  The short fiber nonwoven fabric of the present invention may be either a dry nonwoven fabric or a wet nonwoven fabric as described above. Moreover, if the short fiber of this invention is contained 10 mass% or more, a fabric weight etc. will not be specifically limited.

Since the short fiber of the present invention melts at least a part of the fiber at a temperature lower than the melting point of the polyester, when obtaining the short fiber nonwoven fabric of the present invention, all the short fibers of the present invention are melted. The heat treatment temperature may be appropriately selected according to whether or not only a part is melted.
Further, the heat treatment time may be appropriately selected, and it is also preferable to apply pressure during the heat treatment.

  Note that if the heat treatment temperature is high or the heat treatment time is long, the texture of the resulting nonwoven fabric tends to become stiff and the polymer tends to deteriorate, so the short fiber of the present invention is 100 ° C. lower than the melting point of the polyester. When at least a part is melted, it is preferable to perform heat treatment at a temperature lower by 100 ° C. or more than the melting point of the polyester.

  Next, the manufacturing method of the short fiber for nonwoven fabrics of this invention is demonstrated using an example. Polyester is melt-spun using a commonly used spinning apparatus and wound up without stretching. The obtained undrawn yarn is converged to make a tow of about 1 to 100 ktex, and after being crimped with an indentation type crimper without drawing, a finishing oil is given if necessary, and a desired fiber length To obtain the short fiber of the present invention.

  At this time, in order to satisfy the crimping form defined in the present invention, crimping conditions (nip pressure, stuffing pressure) in a crimping apparatus such as a push-in crimper are appropriately adjusted.

  Further, the short fiber of the present invention is preferably obtained by imparting crimp to an undrawn yarn without substantially drawing after melt spinning, but the birefringence and elongation are adjusted appropriately. It is possible to adjust the spinning speed and spinning temperature.

  Next, about the manufacturing method of the short fiber nonwoven fabric of this invention, each of a dry-type nonwoven fabric and a wet nonwoven fabric is demonstrated using an example. An example in which another fiber is used as the main fiber of the short fiber of the present invention for both the dry nonwoven fabric and the wet nonwoven fabric will be described.

  First, in the case of a dry type non-woven fabric (airlaid method), the short fiber (binder fiber) of the present invention and other short fibers as main fibers are input from the sample input blower 13 using the simple airlaid tester shown in FIG. A set of five first defibrating blades 11 and a second defibrating wing 12 which are rotated by a rotating motor 15 via a defibrating blade rotating sprocket 16 are defibrated and scattered and dropped. While dropping the short fibers are sucked by the suction box 14 at the lower part, they are deposited on the cotton collecting conveyor 17 that moves in the direction of the arrow to create a web, and heat treatment is performed by the heat treatment machine 18 downstream (the present invention). At least some of the short fibers are melted) 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.

  In the case of a wet nonwoven fabric, the short fibers (binder fibers) of the present invention and other short fibers as main fibers are put into a pulp disintegrator and stirred. Thereafter, the obtained sample is transferred to a paper machine, and after adding a dispersion oil mainly composed of an alkyl phosphate metal salt, stirring is performed with an accompanying stirring blade to make a paper, thereby obtaining a wet nonwoven web. The paper-made wet nonwoven web is heat-treated with a hot air dryer (at least a part of the short fibers of the present invention is melted) to obtain a wet nonwoven fabric.

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) Fineness, fiber length, H / L of crimped portion, number of crimps, crimp rate Measured and calculated by the above method.
(4) Birefringence and elongation Measured by the above method.
(5) Formation of fiber masses The short fibers obtained were evaluated for the production of fiber masses using the simple air flow agitator of FIG. 100 g of short fibers are pre-defibrated with a cotton dissipator and then fed into the stirring tank 1 by air flow from the sample feeding blower 3, and an air flow of 20 m / second is blown from the stirring blower 2 to the inside of the stirring tank 1. For 1 minute. 0.1 g of the fiber after stirring was sampled from the sampling port 4 and spread on black paper, and the presence or absence of an independent fiber mass was visually evaluated.
○: Fiber mass is not generated
Δ: A small amount of fiber lump is generated. ×: A large amount of fiber lump is generated. (6) Melted state of fiber 1 g of the obtained fiber is sampled at the temperature of the following 1) to 2) [0035] The same heat treatment was carried out, the state of the fiber after the heat treatment was judged visually, and the following three-stage evaluation was made.
◎ Almost all fibers are melted.
○ Some of the fibers are melted.
X Almost all fibers are not melted.
1) Melting point of polymer-50 ° C
2) Melting point of polymer-100 ° C
(7) Uniformity and bulkiness of non-woven fabric <dry type non-woven 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 ×: Incomplete defibration and non-uniformity-Bulkiness-
The obtained dry nonwoven fabric was cut into 20 cm × 20 cm to make a sample, and 10 cm of the samples were stacked, and an acrylic plate (370 g) of 25 cm × 25 cm × 5 mm was placed thereon, and a 1 kg weight was placed on the acrylic plate. The height of the center of each of the four sides of the lower surface was measured, and the three-level evaluation was performed as follows based on the average value of the four points.
○: Height is 9.0 mm or more
Δ: Height is 8.0 mm or more and less than 9.0 mm
X: Height is less than 8.0 mm -Flexibility-
The obtained dry nonwoven fabric was cut into 20 cm × 20 cm to make a sample, and the softness was evaluated by a three-stage evaluation as follows according to the touch feeling of the panel.
○: Good flexibility
Δ: Somewhat poor flexibility ×: Poor flexibility <wet nonwoven fabric>
-Uniformity-
The uniformity state of the obtained wet nonwoven fabric was observed with the naked eye, and was evaluated in three stages as follows.
○: Sufficiently dispersed and uniform Δ: Partially poorly dispersed portion ×: Insufficient dispersion and non-uniformity-bulkyness-
The obtained wet nonwoven fabric was cut into 20 cm × 20 cm to make a sample, and 10 samples were stacked on top of each other, and a 25 cm × 25 cm × 5 mm acrylic plate (370 g) was placed thereon. The height of the center of each of the four sides of the lower surface was measured, and the three-level evaluation was performed as follows based on the average value of the four points.
○: Height is 8.0 mm or more
Δ: Height is 7.0 mm or more and less than 8.0 mm
X: Height is less than 7.0 mm
-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-stage evaluation as follows according to the touch feeling of the panel.
○: Good flexibility
△: Somewhat poor flexibility ×: Poor flexibility

Example 1
As a polyester, a PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is a round shape having a hole number of 720, using a normal spinning device, at a spinning temperature of 285 ° C., a discharge rate of 190 g / min, and a spinning speed of 1200 m / min. Spinning was performed with a nozzle having a cross section to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 13.3 ktex tow, and then stretched without being drawn, and then crimped with a crimping condition as a crimping condition with a nip pressure of 0.40 MPa and a stuffing pressure of 0.08 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, the tow is cut to obtain a single yarn fineness of 2.2 dtex, A short fiber having a fiber length of 5 mm was obtained.
Table 1 shows the crimped form, number of crimps, crimp rate, birefringence, and elongation of the obtained short fiber.
Next, using a simple air laid tester shown in FIG. 3, a dry nonwoven fabric having a basis weight of 50 g / m ² was obtained as follows. The short fiber obtained as the binder fiber was used, the main fiber shown in Reference Example 1 was used, and the mass ratio of the binder fiber to the main fiber (binder fiber / main fiber) was 40/60.
First, the short fibers fed from the sample feeding blower 13 are defibrated and scattered by a set of five first defibrating blades 11 and second defibrating blades 12 which are rotated by a defibrating blade rotating motor 15 via a defibrating blade rotating sprocket 16. I dropped it. Falling short fibers are sucked by the suction box 14 at the lower part and deposited on a cotton collecting conveyor 17 that moves in the direction of the arrow to create a web, which is then heat treated by a heat treatment machine 18 downstream (heat treatment temperature). : 160 ° C.) to obtain a dry nonwoven fabric. At this time, the basis weight adjustment of the nonwoven fabric was performed by changing the moving speed of the cotton collecting conveyor 17.

Examples 2-7, Comparative Examples 1-4
Various conditions (nip pressure, stuffing pressure) for applying crimping with an indentation type crimper are changed as shown in Tables 1 and 2, and the crimping forms, the number of crimps and the crimping rate shown in Tables 1 and 2 are used. Except that, short fibers were obtained in the same manner as in Example 1.
Using the obtained short fibers, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Example 8
A polyester having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is used as a polyester, and is a round shape having a hole number of 518 using a normal spinning device at a spinning temperature of 285 ° C., a discharge rate of 400 g / min, and a spinning speed of 700 m / min. Spinning was performed with a nozzle having a cross section to obtain an undrawn yarn. The obtained undrawn yarn was converged on a 13.7 ktex tow, and was not stretched, and was applied as it was by using a push-in type crimper with a nip pressure of 0.32 MPa and a stuffing pressure of 0.36 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 11 dtex and a fiber length of 5 mm. Short fibers were obtained.
Table 1 shows the crimped form, number of crimps, crimp rate, birefringence, and elongation of the obtained short fiber.
A dry nonwoven fabric was obtained in the same manner as in Example 1 except that the short fiber obtained as the binder fiber was used and the main fiber shown in Reference Example 2 was used.

Examples 9-13, Comparative Examples 5-8
Various conditions (nip pressure, stuffing pressure) for applying crimping with an indentation type crimper are changed as shown in Tables 1 and 2, and the crimping forms, the number of crimps and the crimping rate shown in Tables 1 and 2 are used. Except that, short fibers were obtained in the same manner as in Example 8.
Using the obtained short fiber, a dry nonwoven fabric was obtained in the same manner as in Example 8.

Example 14
As a polyester, a PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is a round shape having 120 holes under the conditions of a spinning temperature of 285 ° C., a discharge rate of 211 g / min, and a spinning speed of 800 m / min using an ordinary spinning device. Spinning was performed with a nozzle having a cross section to obtain an undrawn yarn. After the obtained undrawn yarn was focused on a 12.7 ktex tow, it was stretched without being drawn, and a crimping condition was applied with a crimping condition of a nip pressure of 0.44 MPa and a stuffing pressure of 0.43 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 22 dtex and a fiber length of 5 mm. Short fibers were obtained.
Table 1 shows the crimped form, number of crimps, crimp rate, birefringence, and elongation of the obtained short fiber.
A dry nonwoven fabric was obtained in the same manner as in Example 1 except that the short fibers obtained as the binder fibers were used, and the main fibers were those shown in Reference Example 3.

Examples 15-19, Comparative Examples 9-12
Various conditions (nip pressure, stuffing pressure) for applying crimping with an indentation type crimper are changed as shown in Tables 1 and 2, and the crimping forms, the number of crimps and the crimping rate shown in Tables 1 and 2 are used. Except that, short fibers were obtained in the same manner as in Example 14.
A dry nonwoven fabric was obtained in the same manner as in Example 14 using the obtained short fibers.

Examples 20-21, Comparative Examples 13-14
Short fibers were obtained in the same manner as in Example 1 except that the fiber length when cutting the tow was changed to the fiber lengths shown in Tables 1 and 2.
Using the obtained short fibers, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Comparative Example 15
Spinning was performed with a nozzle having a round cross section of 720 holes under the conditions of a discharge amount of 272 g / min and a spinning speed of 1200 m / min to obtain an undrawn yarn. Short fibers were obtained in the same manner as in Example 1 except that the obtained undrawn yarn was focused on a 13.6 ktex tow and then drawn with the draw ratio and draw temperature shown in Table 2.
Table 2 shows the crimped form, number of crimps, crimp ratio, birefringence, and elongation of the obtained short fiber.
Furthermore, a dry nonwoven fabric was obtained in the same manner as in Example 1 using the obtained short fibers.

Comparative Example 16
Spinning was performed with a nozzle having a round cross section with 720 holes under the conditions of a discharge amount of 345 g / min and a spinning speed of 1200 m / min to obtain an undrawn yarn. Short fibers were obtained in the same manner as in Example 1 except that the obtained undrawn yarn was focused on a 14.3 ktex tow and then drawn with the draw ratio and draw temperature shown in Table 2.
Table 2 shows the crimped form, number of crimps, crimp ratio, birefringence, and elongation of the obtained short fiber.
Furthermore, a dry nonwoven fabric was obtained in the same manner as in Example 1 using the obtained short fibers.

Comparative Example 17
Spinning was performed with a nozzle having a round cross section with 518 holes under the conditions of a discharge rate of 840 g / min and a spinning speed of 700 m / min, to obtain an undrawn yarn. Short fibers were obtained in the same manner as in Example 8 except that the obtained undrawn yarn was focused on a 14.4 ktex tow and then drawn with the draw ratio and the draw temperature shown in Table 2.
Table 2 shows the crimped form, number of crimps, crimp ratio, birefringence, and elongation of the obtained short fiber.
Further, using the obtained short fibers, a dry nonwoven fabric was obtained in the same manner as in Example 8.

Comparative Example 18
Spinning was performed with a nozzle having a round cross section of 518 holes under the conditions of a discharge amount of 1056 g / min and a spinning speed of 700 m / min, to obtain an undrawn yarn. Short fibers were obtained in the same manner as in Example 8 except that the obtained undrawn yarn was focused on a 13.6 ktex tow and then drawn with the draw ratio and draw temperature as shown in Table 2.
Table 2 shows the crimped form, number of crimps, crimp ratio, birefringence, and elongation of the obtained short fiber.
Further, using the obtained short fibers, a dry nonwoven fabric was obtained in the same manner as in Example 8.

Comparative Example 19
Spinning was performed with a nozzle having a round cross section with 120 holes, under the conditions of a discharge rate of 458 g / min and a spinning speed of 800 m / min, to obtain an undrawn yarn. Short fibers were obtained in the same manner as in Example 14 except that the obtained undrawn yarn was focused on a 13.7 ktex tow and then drawn with the draw ratio and draw temperature as shown in Table 2.
Table 2 shows the crimped form, number of crimps, crimp ratio, birefringence, and elongation of the obtained short fiber.
Furthermore, using the obtained short fibers, a dry nonwoven fabric was obtained in the same manner as in Example 14.

Comparative Example 20
Spinning was performed with a nozzle having a round cross section with 120 holes under the conditions of a discharge rate of 574 g / min and a spinning speed of 800 m / min to obtain an undrawn yarn. Short fibers were obtained in the same manner as in Example 14 except that the obtained undrawn yarn was focused on a 14.4 ktex tow and then drawn with the draw ratio and draw temperature shown in Table 2.
Table 2 shows the crimped form, number of crimps, crimp ratio, birefringence, and elongation of the obtained short fiber.
Furthermore, using the obtained short fibers, a dry nonwoven fabric was obtained in the same manner as in Example 14.

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 given as 0.09 MPa. Thereafter, a spinning oil mainly composed of polyoxyethylene alkyl ether as a finishing oil was applied so as to have an adhesion amount of 0.2% by mass, and then cut to a single yarn fineness of 2.2 dtex and a fiber length of 5 mm. Fiber was obtained.

Reference example 2
Polyester having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is used as a polyester, using a normal melt spinning apparatus, spinning temperature of 285 ° C., discharge amount of 328 g / min, spinning speed of 600 m / min, and round of 120 holes. Spinning was performed with a nozzle having a mold section to obtain an undrawn yarn. The resulting undrawn yarn was focused on a toe of 14.2 ktex, then drawn at a draw ratio of 4.14 times and a draw temperature of 75 ° C., and a crimping condition was applied by a push-in crimper with a nip pressure of 0.35 MPa and a stuffing pressure. Crimping was given as 0.30 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 obtain a short fiber having a single yarn fineness of 11 dtex and a fiber length of 5 mm. Obtained.

Reference example 3
As polyester, a PET having a melting point of 256 ° C. and an intrinsic viscosity of 0.61 is obtained by using a normal melt spinning apparatus, spinning conditions of 285 ° C., discharge amount of 283 g / min, spinning speed of 900 m / min, and round of 40 holes. Spinning was performed with a nozzle having a mold section to obtain an undrawn yarn. The resulting undrawn yarn was focused on a 14.0 ktex tow, then drawn at a draw ratio of 3.57 times and a draw temperature of 80 ° C., and a crimping condition was applied by a push-in crimper with a nip pressure of 0.45 MPa and a stuffing pressure. Crimping was given as 0.35 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 obtain a short fiber having a single yarn fineness of 22 dtex and a fiber length of 5 mm. Obtained.

  Tables 1 and 2 show measured values and evaluation results of the short fibers obtained in Examples 1 to 21, Comparative Examples 1 to 23, and Reference Examples 1 to 3. Tables 1 and 2 show the evaluation results of uniformity, bulkiness, and flexibility when a dry nonwoven fabric is prepared using these short fibers.

  As apparent from Tables 1 and 2, since the short fibers of Examples 1 to 21 satisfied the formula (1), in particular, Examples 1 to 5, 8 to 11, 14 to 17, 20 to 20 Since the short fiber No. 21 satisfied the formulas (1) to (3), no static electricity was generated or static electricity was accumulated, and no fiber lump was generated. In addition, since the birefringence and the elongation satisfy the scope of the present invention, they have the ability to melt at a heat treatment temperature lower than the melting point of the polyester, and the obtained dry nonwoven fabric is The short fibers were almost completely melted by heat treatment (to become all-fused binder fibers), and the main fibers were well bonded. Furthermore, the obtained dry nonwoven fabric was excellent in uniformity, bulkiness and flexibility.

  On the other hand, since the H / L ratio of the short fibers of Comparative Examples 1, 3, 5, 7, 9, and 11 is larger than the range of the formula (1), all of them easily accumulate static electricity, and the fibers are entangled. A ball-shaped fiber mass was formed. Therefore, the obtained dry nonwoven fabric was non-uniform and inferior in quality and poor in flexibility.

  Moreover, since the H / L ratio of the short fibers of Comparative Examples 2, 4, 6, 8, 10, and 12 is smaller than the range of the formula (1), the contact points (surfaces) between the fibers and between the fibers and the machine. ), The generation of static electricity increased, and a ball-like fiber lump was formed. For this reason, the obtained dry nonwoven fabric is non-uniform and inferior in quality, and has poor flexibility. Moreover, since the short fiber of the comparative example 13 had too short fiber length, the close_contact | adherence of the fiber generate | occur | produced with the frictional heat at the time of fiber cutting, and the nonwoven fabric was not able to be obtained. Since the short fiber of Comparative Example 14 was too long, it was easy to accumulate static electricity, and entanglement of the fiber also occurred, resulting in a ball-like fiber lump. Thus, the obtained dry nonwoven fabric was uneven and inferior in quality. There was a lack of flexibility.

  The short fibers of Comparative Examples 15 to 20 were obtained by drawing undrawn yarn, and the birefringence and elongation did not satisfy the scope of the present invention, so the heat treatment temperature lower than the melting point of the polyester. The fiber was not melted by heat treatment when obtaining a dry nonwoven fabric, and did not become a binder fiber, so that the main fiber was not adhered and the nonwoven fabric could not be obtained.

Examples 22-26, Comparative Examples 21-25
The short fibers of Examples 1 to 5, Comparative Examples 1 to 4 and Comparative Example 15 were used as binder fibers, and the main fibers shown in Reference Example 1 were used to prepare wet nonwoven fabrics as follows.
The binder fiber and the main fiber were made into a mass ratio (binder fiber / main fiber) of 30/70, charged into a pulp disintegrator (manufactured by Kumagaya Riken Kogyo), and stirred at 3000 rpm for 1 minute. After that, the obtained sample was transferred to a paper machine (Kumagaya Riki Kogyo's square sheet machine), and after adding a dispersion oil mainly composed of an alkyl phosphate metal salt, stirring was performed with an accompanying stirring blade to make the paper. And it was set as the wet nonwoven fabric web. The paper-made 25 × 25 cm wet nonwoven web was heat-treated at 150 ° C. for 10 minutes with a box-type hot air dryer to obtain a wet nonwoven fabric having a basis weight of 50 g / m ² .
Table 3 shows the evaluation results of uniformity, bulkiness and flexibility of the obtained wet nonwoven fabric.

  As is apparent from Table 3, the short fibers of Examples 22 to 26 satisfied the formulas (1) to (3), and therefore had good dispersibility in water and no fiber convergence. For this reason, the obtained wet nonwoven fabric was excellent in uniformity, bulky and flexible.

  On the other hand, since the short fiber of Comparative Example 21 had an H / L ratio larger than the range of the formula (1), the number of crimps and the crimp rate were larger than the ranges of the formulas (2) and (3). These short fibers had an H / L ratio larger than the range of the formula (1) and further had a crimping ratio larger than the range of the formula (3). Therefore, the obtained wet nonwoven fabric was non-uniform, inferior in quality, and poor in flexibility. Further, since the short fiber of Comparative Example 22 has an H / L ratio smaller than the range of the formula (1), the crimp number and the crimp rate are smaller than the ranges of the formulas (2) and (3). These short fibers have an H / L ratio smaller than the range of the formula (1), and further, the crimp ratio is smaller than the range of the formula (3). Since the uniformity and bulkiness were insufficient, the obtained non-woven fabric was also inferior in uniformity and bulkiness and had poor flexibility. Moreover, since the short fiber of Comparative Example 25 did not satisfy the scope of the present invention in terms of birefringence and elongation, the fiber was not melted by heat treatment when obtaining a wet nonwoven fabric, and thus did not become a binder fiber. The main fiber was not adhered, and a nonwoven fabric could not be obtained.

Examples 27-31, Comparative Example 26
As shown in Table 4, the short fibers of Example 1 are used as the binder fibers, the short fibers of Reference Example 1 are used as the main fibers (other fibers), and the mass ratio of the main fibers to the binder fibers (main fibers / binder fibers) is shown in Table 4. A dry nonwoven fabric was obtained in the same manner as in Example 1 except that various changes were made. At this time, almost all of the short fibers of the present invention were melted by the heat treatment, and became all-fused binder fibers.
Table 4 shows the evaluation results of uniformity, bulkiness and flexibility of the obtained dry nonwoven fabric.

  As apparent from Table 4, the dry nonwoven fabrics of Examples 27 to 31 were excellent in uniformity, bulkiness, and flexibility because they contained 10% by mass or more of the short fibers of the present invention. The dry nonwoven fabric of Example 31 was excellent in uniformity because the short fibers of the present invention were all-melted binder fibers and contained 80% by mass of the short fibers of the present invention, but bulkiness and flexibility were not good. It was enough.

  On the other hand, the dry nonwoven fabric of Comparative Example 26 did not contain 10% by mass or more of the short fibers of the present invention, so the main fibers did not adhere to each other and could not be made into a nonwoven fabric.

Examples 32-36, Comparative Example 27
As shown in Table 4, the short fibers of Example 1 are used as the binder fibers, the short fibers of Reference Example 1 are used as the main fibers (other fibers), and the mass ratio of the main fibers to the binder fibers (main fibers / binder fibers) is shown in Table 4. A wet nonwoven fabric was obtained in the same manner as in Example 22 except that various changes were made.
Table 5 shows the evaluation results of uniformity, bulkiness and flexibility of the obtained wet nonwoven fabric.

  As is apparent from Table 5, the dry nonwoven fabrics of Examples 32-36 contained 10% by mass or more of the short fibers of the present invention, and thus were excellent in uniformity, bulkiness and flexibility. The dry nonwoven fabric of Example 36 was excellent in uniformity because the short fibers of the present invention were all-melted binder fibers and contained 80% by mass of the short fibers of the present invention, but was not bulky and flexible. It was enough.

  On the other hand, since the dry nonwoven fabric of Comparative Example 27 did not contain 10 mass% or more of the short fibers of the present invention, the main fibers did not adhere to each other and could not be made into a nonwoven fabric.

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 test machine for evaluating the production | generation of the fiber lump in an Example. It is explanatory drawing which shows the simple airlaid tester which manufactured the dry-type nonwoven fabric in the Example.

Claims (6)

A short fiber made of polyester mainly composed of an alkylene terephthalate unit, having a fiber length of 1.0 to 30 mm, a single yarn fineness of 1.0 to 40 dtex, a birefringence of 0.0150 or less, an elongation of 250% or more, and a crimp. In the maximum peak portion of the crimped portion where the crimped form of the single yarn is the height (H) and the bottom side (L) of the triangle connecting the two vertexes of the valleys adjacent to the peak of the peaks A short fiber for nonwoven fabric, characterized in that the ratio (H / L) satisfies the following formula (1):
(1) Formula: 0.01T + 0.1 ≦ H / L ≦ 0.02T + 0.25
T is the number of decitex (dtex) of single yarn fineness The short fiber for nonwoven fabric 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. T is the number of decitex (dtex) of single yarn fineness. The short fiber for nonwoven fabric according to claim 1 or 2, wherein the melting point of the polyester mainly composed of an alkylene terephthalate unit is 220 ° C or higher. The short fiber for nonwoven fabric according to any one of claims 1 to 3, wherein at least a part of the fiber melts when heat-treated at a temperature lower by 50 ° C than the melting point of the polyester mainly composed of an alkylene terephthalate unit. The short fiber for nonwoven fabric according to any one of claims 1 to 4, which is obtained by imparting crimp to an undrawn yarn without substantially drawing after melt spinning. A short fiber nonwoven fabric comprising 10% by mass or more of the short fiber for nonwoven fabric according to any one of claims 1 to 5.