JPH0434058A - Production of nonwoven fabric of ultrafine short fiber - Google Patents

Abstract

PURPOSE:To obtain the subject nonwoven fabric having high strength and soft feeling and suitable as a material for medical and hygienic use in high efficiency at a low cost by treating a conjugate fiber composed of a polyolefin polymer component and a specific polymer component with a specific treating method. CONSTITUTION:A binary conjugate fiber composed of (A) a polyolefin polymer component and (B) a polymer component incompatible with the component A and having a melting point higher than that of the component A by >=20 deg.C is produced by composite melt-spinning and is drawn and collected. The obtained undrawn fiber bundle is drawn, crimped by mechanical crimping and cut into short fibers. A web made of the short fibers is treated with a high-pressure liquid jet stream to release at least a part of the segment composed of the component B from the above short fiber to form a split short fiber having a single fiber fineness of <=0.7 denier and, at the same time, three-dimensional entanglements are introduced between the short fibers to integrate the fibers. Finally, the obtained web is heat-treated at a temperature above the melting point of the component A to bond the short fibers with the short fiber of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a nonwoven fabric, and more specifically,
The present invention relates to a method for producing an ultrafine short fiber nonwoven fabric that has a soft texture and can be suitably used for medical hygiene materials.

(Prior Art) In recent years, short fiber nonwoven fabrics have been used for medical sanitary materials, particularly for disposable diapers, sanitary napkins, and the like.

Since these short fiber nonwoven fabrics are usually composed of short fibers having a single filament fineness of about 1.5 denier, they have a problem of poor texture, that is, they feel hard to the touch when used. In order to improve the texture,
Attempts have been made to obtain a nonwoven fabric made of ultrafine short fibers having a single filament fineness of about 0.5 denier. For example, JP-A-62-
In Publication No. 133164.

A method is disclosed for obtaining a nonwoven fabric composed of ultrafine staple fibers by treating composite staple fibers with a high-pressure liquid stream to split and fibrillate them. however.

This nonwoven fabric manufacturing method uses ultrafine staple fibers with a single filament fineness of about 0.5 denier, so opening properties are not improved.

It is difficult to increase the opening speed, and therefore productivity is significantly reduced. This has the problem of increased production costs. In addition, although the obtained nonwoven fabric has a soft feel due to the formation of entanglements between the short fibers due to the high-pressure liquid flow treatment, it has a problem of low tenacity because the short fibers are not thermally bonded. ing.

(Problems to be Solved by the Invention) The present invention solves the above problems and makes it possible to efficiently produce an ultrafine short fiber nonwoven fabric that has a flexible texture and can be suitably used for medical sanitary materials. It is intended to provide a method.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the inventors have found
We have arrived at the present invention. In other words, one aspect of the present invention is.

Melting a bicomponent composite fiber consisting of a polyolefin polymer component A and a polymer component B that is incompatible with the polyolefin polymer component A and has a melting point at least 20° C. higher than the melting point of the polymer component A. After composite spinning, the undrawn fiber yarns of the spun bicomponent composite fibers are collected and bundled to form an undrawn fiber yarn bundle.1.The obtained undrawn fiber yarn bundle is then stretched. After applying mechanical crimping, the fibers are cut into a predetermined fiber length to obtain two-component composite staple fibers, a web is created using the two-component composite staple fibers, and the resulting web is treated with a high-pressure liquid columnar flow. At least a portion of the segment made of the polymer component B having a high melting point is exfoliated from the composite staple fiber to produce a split staple fiber having a single filament fineness of 0.7 denier or less, and three-dimensional entanglement is caused between the staple fibers. 9. Next, the short fibers made of the low melting point polymer component A are at least partially bonded together by heat treatment at a temperature higher than the melting point of the low melting point polymer component A. The gist of the present invention is a method for producing a nonwoven fabric characterized by the following.

Next, one aspect of the present invention will be explained in detail.

The polyolefin polymer component A, which is one component of the two-component composite staple fiber in the present invention, has fiber-forming ability and can be melt-spun using a normal melt-spinning device. , low-density polyethylene (LDPB), direct-set low-density polyethylene (LL[1PB), high-density polyethylene (HDPB), polypropylene, modified polyethylene or modified polypropylene made by copolymerizing ethylene or propylene with unsaturated carboxylic acid such as acrylic acid, etc. etc. On the other hand, polymer component B, which is another component, is a polyester polymer or polyamide polymer that is incompatible with the former 8-polyolefin polymer component A, and both have fiber-forming ability and 1 The polyester polymer can be melt-spun using an ordinary melt-spinning device. Examples of the polyester polymer include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and copolyesters containing these as main components. Examples of the acid component of the copolymerized polyester include carboxylic acids such as isophthalic acid and adipic acid, and examples of the glycol component include glycols such as neopentyl glycol. Also,
Polyamide polymers include nylon 6° and nylon 4.
6. Nylon 66, nylon 610. Examples include polyamides such as Suyron 12 and copolymerized nylons containing these as main components. Further, as long as monopolymer acid components A and B exhibit incompatibility between the components of one fraction, the above-mentioned compounds may be used alone or in a mixture of two or more thereof. Note that each of the polymer acid components A and B may contain one or more conventional additives such as a matting agent, a heat stabilizer, a pigment, or a polymer crystallization accelerator.

Polymer component B, which is one component of the two-component composite short fiber in the present invention, needs to have a melting point that is at least 20° C. higher than the melting point of polymer component A, which is another component. The melting point of a polymer as used in the present invention is measured using a differential calorimeter DSC-2 manufactured by PerkinElmer, according to the manual of the device, with a sample amount of approximately 5 mg and a scanning speed of 20°C/min. It was determined from the obtained DSC curve. If the melting point difference between polymer component B and polymer component A is less than 20°C, the heat deformation temperature ranges of one component will overlap, and when the web is heat treated with a heat treatment device, polymer component B with a high melting point will be deformed or This is not preferable because problems such as melting and deterioration of the strength and texture of the obtained nonwoven fabric occur.

The two-component composite short fiber as used in the present invention is composed of the polymer component A and the polymer component B. Figure 1 is a cross-sectional view showing an example of the two-component composite short fiber referred to in the present invention. Figure 1 shows an example in which 4 and 3 pieces are added to , respectively (
C) is an example in which 9 polymer acid components A and B are arranged radially and alternately on the circumference, and Figure 1 (d) is an example in which 1 polymer acid components A and B are arranged radially and alternately on the circumference. This is an example in which a hollow part is provided.

Monopolymer acid content B in the two-component composite short fibers referred to in the present invention
The number of segments is two or more, preferably four or more. If the number of this segment is one, crimping may occur in the composite short fibers depending on spinning conditions or drawing conditions, and when forming into a web, the spreadability of the fibers decreases, making it impossible to obtain a uniform web. , undesirable. In addition, if the number of segments is large, the advantage of splitting will be improved, but if there is too many segments, the cross-sectional structure will be such that segments made only of polymer component B are adhered to each other, making it difficult to split and peel them in the subsequent process. Usually about 1,8
It is best to limit it to about 100 pieces.

The method for producing the ultrafine short fiber nonwoven fabric of the present invention is as follows.

The polymer component A is incompatible with the polymer component A and is at least 20° C. above the melting point of the polymer component A.
A bicomponent composite fiber made of polymer component B having a high melting point is melt-composite-spun using a conventional melt-composite spinning lid, and the undrawn fiber threads of the spun bicomponent composite fiber are collected. The fibers are pulled by a bowing means such as a roll and then bundled to form an undrawn fiber yarn bundle. Next, the obtained undrawn fiber yarn bundle is drawn and mechanically crimped, and then cut into a predetermined fiber length to obtain a two-component composite short fiber.

Next, a web is created using the two-component composite short fibers,
By treating the obtained web with a high-pressure liquid columnar flow, at least a portion of the segments made of the polymer component B having a high melting point are exfoliated from the composite short fibers, and the single fiber fineness is reduced to 0.
．． The split short fibers are 7 denier or less, and at the same time, the short fibers are three-dimensionally entangled and integrated. When forming a web, after cutting the melt-spun undrawn fiber yarn bundle, the fibers are spread by a spreading means such as a card, and the resulting web is deposited on a collecting surface of a moving net conveyor, etc. let High-pressure liquid columnar flow treatment is a process in which a high-pressure liquid columnar flow collides with the web surface to split the two-component composite short fibers using stresses such as shearing, elongation, and compression, and at the same time create three-dimensional entanglements between the short fibers. They are integrated by combining them. The liquid used may be water at room temperature or warm water. As a nozzle for injecting a columnar flow of liquid, it is preferable to use a nozzle having a hole diameter of 0.05 to 1.0, preferably 0.1 to 0.4. The injection pressure is 5 to 150
kg/cm! G, preferably 10 to 100 kg/c
I]! It is better to set it as G.

If the injection pressure is less than 5 kg/Cr1G, the segments made of the polymer component B cannot be sufficiently exfoliated, which is not preferable. The distance between the nozzle and the web is 1~
The distance is preferably 15 cm, preferably 3 to 13 cm. If this distance becomes too large, air will be mixed into the liquid columnar flow, reducing the effect of three-dimensional entanglement, which is not preferred.

Next, heat treatment is performed at a temperature equal to or higher than the melting point of the low melting point polymer component A to at least partially bond the short fibers together using the short fibers made of the low melting point polymer component A to obtain a nonwoven fabric. In addition.

The obtained nonwoven fabric may be subjected to a softening process to improve the flexibility of the nonwoven fabric. In the heat treatment, it is preferable to use a device that can sufficiently heat the inside of the web; for example, a hot air circulation dryer, an infrared heating device, etc. can be used. FIG. 2 is a process diagram showing an example of the manufacturing method of the present invention.

1 is a web, 2 is a net conveyor, 3 is a liquid columnar flow jet nozzle, 4 is a suction box, 5 is a dryer, 6 is a heat treatment machine, and 7 is a nonwoven fabric.

Next, the ultrafine short fiber nonwoven fabric obtained by the manufacturing method of the present invention will be explained.

The ultrafine short fiber nonwoven fabric obtained by the production method of the present invention is
(a) a bicomponent composite short fiber made of a polymer component A and a polymer component B that is incompatible with the polymer component A; and (b) a segment made of a polymer component B from the bicomponent composite staple fiber. Partially exfoliated two-component composite short fibers; (c) Split short fibers consisting only of the polymer component A developed by splitting the two-component composite short fibers; (d) Consisting only of the polymer component B. It is composed of split short fibers.

The ultrafine short fiber nonwoven fabric obtained by the production method of the present invention is
The splitting ratio of the segments made of the polymer component B is at least 80%. This splitting ratio is (a)
A two-component composite short fiber, (b) a two-component composite short fiber in which a segment made of polymer component B is partially exfoliated from the two-component composite short fiber, and (c) a two-component composite short fiber developed by splitting the two-component composite short fiber. Ten arbitrary locations of the nonwoven fabric composed of split short fibers made only of the polymer component A and (d) split short fibers made only of the polymer component B are selected, and the cross section of the nonwoven fabric is enlarged. Take a cross-sectional photograph and then take a cross-sectional photograph.

It is calculated by determining the total number of segments of polymer component B that are exfoliated from the composite short fibers and the total number of segments of polymer component B that are present. It represents the ratio (%) of the total number of segments of combined component B. Since the ultrafine short fiber nonwoven fabric obtained by the production method of the present invention has a soft texture, the fiber splitting ratio is at least 80%.
%, and if the fiber splitting ratio is less than 80%, the flexibility will be poor when made into a nonwoven fabric, which is not preferable.

Further, the split short fibers are composed only of the polymer component B developed by splitting the composite short fibers.

It is preferable that the single yarn fineness is 0.7 denier or less, preferably 0.5 denier or less. Even if the splitting ratio is 80% or more, if the single fiber fineness of the splitting short fibers made of one polymer component B exceeds 0.7 denier, a nonwoven fabric with a flexible texture cannot be obtained, Undesirable.

(Example) Next, the present invention will be specifically described based on Examples. In addition, various characteristics in the examples were measured by the primary method.

Relative viscosity: What is the relative viscosity of polyester polymers?

Using a mixed solution of equal weights of phenol and tetrachloroethane as a solvent, the measurement was performed at a sample concentration of 0.5 g/100 mf and a temperature of 20°C.

Relative viscosity: What is the relative viscosity of polyamide polymers?

Using sulfuric acid with a concentration of 96% by weight as a solvent, the sample concentration was 0.5g1
50-1 Measured at a temperature of 25°C.

Melt flow rate: Measured by ASTM DI238L method.

Melting point: Determined from a DSC curve obtained by measuring a sample amount of about 5 mg at a scanning speed of 20° C./min using a differential scanning calorimeter model DSC-2 manufactured by Birkin Elma.

Tensile strength in vertical direction of non-woven fabric Width is 25mm, length is 10mm
A measurement sample piece of 0.0 cm was prepared and measured by the strip method described in JIS L-1096.

A measurement sample piece with a compressive bending strength of 50 mm and a length of 100 mm was prepared, and this sample piece was sized with a height of 50 mm and a circumference of 1.
00 = cylindrical shape and placed on a flat plate type load cell.

The cylindrical sample piece was compressed at a speed of 50 cycles per minute, the maximum load was determined, and the obtained value was taken as the compression stiffness.

Fabric weight: Measured by the method described in JIS P-8142.

Example 1 Melting point: 130°C, melt flow rate: 20 g/
A 10-minute polyethylene polymer was used as polymer component A, a polyethylene terephthalate polymer with a melting point of 260°C and a relative viscosity of 1.38 was used as polymer component B, and the composite spinning hole was 319.
The bicomponent composite fibers were melt spun through a spinneret with holes at a spinning temperature of 270°C. Nine polymer acid content A during melt spinning
The single hole discharge rate of the polymer component B was set to 0.125 g/min. After the spun composite fiber yarn was cooled, it was taken up by a take-up roll having a circumferential speed of 1000 m 2 /min to obtain a package of undrawn fiber yarn. The obtained package was bundled into a tow of 100,000 denier, stretched at a stretching temperature of 75°C and a stretching ratio of 2.8, and then mechanically crimped with a push-in crimper to a length of 5.
Two-component composite short fibers were obtained by cutting into 1 mm pieces. The short fibers had a single fiber fineness of 2 denier and were as shown in FIG. 1(a).

It had a cross-sectional shape in which four polymer components B were added in a petal shape around polymer component A and nine polymer acid components A.

Next, the two-component composite short fibers were opened at a speed of 50 m/min using a roller card to create a web with a basis weight of 40 g/g, as shown in FIG.

The resulting web was deposited on the surface of a moving net conveyor at a speed of 10 m/min and treated with two successive high-pressure water columns. This processing condition is such that the injection nozzle hole diameter is 0.15m.
m, and the nozzle hole arrangement interval is 1. Omm, the number of nozzle hole rows is 2
．． The pressure in the first row of nozzle holes was 20 kg/rtx"G, the pressure in the second row of nozzle holes was 40 kg/m"G, and the distance between the nozzle and the web was 100 mm, and the injection treatment was performed from the web side. In addition, when performing this treatment, the water used for spraying was collected and removed using a suction box.

Continuing with the high-pressure water column flow treatment, the web was subjected to heat treatment using a dryer. What are the processing conditions?

The treatment temperature was 150° C. and the treatment time was 1 minute.

The obtained nonwoven fabric had a basis weight of 45 g/m', a longitudinal tensile strength of 9.2 kg/3 cm, and a compression stiffness of 7.
It was 3g. Select 10 arbitrary locations on the nonwoven fabric, enlarge the cross section of the nonwoven fabric, and take cross-sectional photographs. Next, in the 10 cross-sectional photographs, determine the total number of segments of polymer component B that have peeled off from the composite short fibers. When the total number of segments of polymer component B was determined and the 10% fiber ratio was determined, the 100% fiber ratio was 97%. This nonwoven fabric includes (d) split staple fibers made only of the polymer component B, and (i) two-component composite short fibers in which segments made of the polymer component B have not been peeled at all.

(b) two-component composite short fibers in which segments made of polymer component B are partially exfoliated from the two-component composite short fibers; and (c)
Split short fibers composed only of the polymer component A developed by splitting the two-component composite short fibers were observed.

Further, when the single fiber fineness of the split short fibers composed only of the polymer component B developed by splitting the composite short fibers was determined, it was found to be extremely fine at 0.37 denier. This nonwoven fabric had a soft touch.

Comparative Example 1 Two-component composite short fibers were obtained in the same manner as in Example 1, except that no heat treatment was performed, and the fibers were opened using a roller card to create a web with a basis weight of 40 g/m''. The resulting web was treated with a high-pressure water column twice in succession to obtain a nonwoven fabric.

The obtained nonwoven fabric has a basis weight of 38 g/m'', a longitudinal tensile strength of 6.3 kg/3 cm, and a compression stiffness of 6.5.
g, and although it had excellent flexibility, it had low strength due to the fact that the short fibers were not bonded together.

Example 2 Melting point is 170°C, melt flow rate value is 50g/10
Polypropylene polymer of 100% was used as polymer component A.

The two-component composite filament was melt-spun in the same manner as in Example 1 except that the melting temperature was 270°C, and the undrawn fiber yarn package was obtained by taking it off with a take-up roll. were collected and bundled to form a 100,000 denier tow, stretched at a stretching temperature of 75°C and a stretching ratio of 2.9, and then mechanically crimped with a push-in crimper to a length of 5.
Two-component composite short fibers were obtained by cutting into 1 mm pieces. This short fiber has a single filament fineness of 2 denier, and as shown in Figure 1(a), four polymer components B are arranged around nine polymer components A and one polymer acid component A in a petal shape. It had an additional cross-sectional shape.

Next, in the same manner as in Example 1, the two-component composite short fibers were opened using a roller card to obtain a basis weight of 40 g/m''.
After creating a web of
It was deposited on the surface of a net conveyor moving at a speed of 1/2 min and treated with two consecutive high-pressure water column flows.

Continuing with the high-pressure water column flow treatment, the web was subjected to heat treatment using a dryer. What are the processing conditions?

The treatment temperature was 170° C. and the treatment time was 1 minute.

The obtained nonwoven fabric has a basis weight of 43 g/rn'', a longitudinal tensile strength of 9-5 kg/3 cm, and a compression stiffness of 7.
It was 3g. When 10 arbitrary points of the nonwoven fabric were selected and the 10% fiber ratio was determined, the 40% fiber ratio was 95%. This nonwoven fabric includes (d) split staple fibers made only of the polymer component B, (b) two-component composite short fibers with no exfoliated segments made of the polymer component B, and ( B)
(c) a two-component conjugate short fiber in which a segment made of polymer component B is partially exfoliated from the two-component conjugate short fiber;
The polymer component A expressed by splitting component composite short fibers
It was recognized that split short fibers were composed only of Also,
When the single fiber fineness of split short fibers composed only of polymer component B developed by splitting the composite short fibers was determined,
It was extremely thin with an OJ5 denier. This nonwoven fabric had a soft touch.

Comparative Example 2 Two-component composite short fibers were obtained in the same manner as in Example 2, except that no heat treatment was performed, and the fibers were opened using a roller card to create a web with a basis weight of 40 g/m. The resulting web was treated with a high-pressure water column twice in succession to obtain a nonwoven fabric.

The obtained nonwoven fabric has a basis weight of 38 g/m'', a longitudinal tensile strength of 6.8 kg/3 cm, and a compression stiffness of 6.9.
g, and although it had excellent flexibility, it had low strength because the short fibers were not bonded.

Example 3 Nylon hexapolymer with a melting point of 217°C and a relative viscosity of 3.09 (manufactured by Unitika Co., Ltd., trade name A 1030B RF)
) was used as polymer component B and the melting temperature was 265°C, but in the same manner as in Example 1, the two-component composite filament was melt-spun and taken off with a take-up roll to obtain a package of undrawn fiber yarn. The obtained packages were collected and bundled into a 100,000 denier tow, and the stretching temperature was set to 75°C and the stretching ratio was 2.
．． After stretching at step 6 and mechanically crimp using a push-in crimper at step 9, the fibers were cut into a length of 51 mm to obtain a two-component composite short fiber. This short fiber has a single fiber fineness of 2 denier, and as shown in Figure 1(a), four polymer components B are arranged around one polymer acid component A and nine polymer acid components A. It had a cross-sectional shape added to the shape.

Next, in the same manner as in Example 1, the two-component composite short fibers were opened using a roller card to give a basis weight of 40 g/
After creating a web of m', the resulting web is deposited on the surface of a moving net conveyor at a speed of 10 m/min,
Two consecutive treatments were carried out with high pressure water column flow.

Continuing with the high-pressure water column flow treatment, the web was subjected to heat treatment using a dryer. What are the processing conditions?

The treatment temperature was 150° C. and the treatment time was 1 minute.

The obtained nonwoven fabric has a basis weight of 47 g/m'', a longitudinal tensile strength of 8.9 kg/3 cm, and a compression stiffness of 4.8.
It was g. When 10 arbitrary points of the nonwoven fabric were selected and the 10% fiber ratio was determined, the 90% fiber ratio was 90%. Also.

When the single fiber fineness of split short fibers composed only of polymer component B developed by splitting the composite short fibers was determined,
, OJ9 denier and extremely thin. and,
This nonwoven fabric was extremely soft to the touch.

Example 4 The two-component composite short fiber obtained in Example 1 and the melting point of 110
Example 1 was carried out in the same manner as in Example 1, except that the web was created using a mixture of 10% by weight of binder fiber (manufactured by Unitika Co., Ltd., trade name: Meltei) at 10°C.

A non-woven fabric was created.

The obtained nonwoven fabric has a basis weight of 45 g/m', a longitudinal tensile strength of 15.3 kg/3 cm, and a compression stiffness of 9.
It had a weight of 2g, high strength, and a soft touch.

Example 5 Binder fiber (manufactured by Unitika Co., Ltd., trade name Meltei)
A nonwoven fabric was produced in the same manner as in Example 1, except that the cotton blend ratio was 20% by weight.

The obtained nonwoven fabric has a basis weight of 48 g/m', a longitudinal tensile strength of 17.8 kg/3 cm, and a compression stiffness of 12.
．． It had a weight of 5 g, high strength, and a soft touch.

Comparative Example 3 Binder fiber (manufactured by Unitika Co., Ltd., trade name Meltei)
A nonwoven fabric was produced in the same manner as in Example 4, except that the cotton blend ratio was 40% by weight.

The obtained nonwoven fabric has a basis weight of 51 g/m'', a longitudinal tensile strength of 24.0 kg/3 cm, and a compression stiffness of 33.
．． 0g, and although it had extremely high strength, the adhesion between the short fibers was too strong, resulting in low flexibility.

(Effect of the invention) According to the method for producing an ultrafine short fiber nonwoven fabric of the present invention.

It is composed of two-component composite short fibers and split short fibers developed by splitting the two-component composite short fibers, and the short fibers are at least partially adhered by the short fibers made of a low melting point polymer component. Strong and excellent.

Moreover, a nonwoven fabric having a soft texture can be efficiently produced at low cost.

The obtained nonwoven fabric can be suitably used as a material for medical hygiene materials.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the two-component composite short fiber according to the present invention, and FIG. 2 is a process diagram showing an example of the manufacturing method according to the present invention. 1: Web, 2: Net conveyor, 3: Liquid columnar flow jet nozzle, 5: Dryer, 6: Heat treatment machine. 7: Nonwoven fabric patent applicant Nippon Ester Co., Ltd.

Claims (4)

[Claims] (1) A two-component composite consisting of a polyolefin polymer component A and a polymer component B that is incompatible with the polyolefin polymer component A and has a melting point at least 20°C higher than the melting point of the polymer component A. The fibers are melt-composite-spun, the undrawn fiber yarns of the spun bicomponent composite fibers are collected and bundled into undrawn fiber yarn bundles, and then the obtained undrawn fiber yarn bundles are collected. After being stretched and mechanically crimped, the fibers are cut into a predetermined fiber length to obtain two-component composite short fibers, a web is created using the two-component composite short fibers, and the obtained web is treated with a high-pressure liquid columnar flow. By doing so, at least a portion of the segment made of the polymer component B having a high melting point is exfoliated from the composite short fibers to obtain split short fibers having a single filament fineness of 0.7 denier or less, and a three-dimensional structure is formed between the short fibers. By entanglement and integration, and then heat treatment at a temperature higher than the melting point of the low melting point polymer component A, the short fibers made of the low melting point polymer component A are used to at least partially connect the short fibers. A method for producing an ultrafine short fiber nonwoven fabric characterized by adhesion. (2) The ultrafine according to claim 1, wherein the polyolefin polymer component A constituting the two-component composite staple fiber is a polyethylene polymer or a polypropylene polymer, and the polymer component B is a polyester polymer or a polyamide polymer. A method for producing short fiber nonwoven fabric. (3) Claim 1 or 2, wherein the split short fibers are ultrafine short fibers having a single filament fineness of 0.5 denier or less, which is composed only of the high melting point polymer component B developed by splitting the bicomponent composite short fibers. The method for producing the ultrafine short fiber nonwoven fabric described above. (4) 30% by weight or less of binder fibers having a melting point lower than the melting point of the polymer component A constituting the two-component composite short fibers are blended with the two-component composite staple fibers. Or the method for producing an ultrafine short fiber nonwoven fabric according to 3.