JPH09119050A - Combined filament yarn nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a combined filament yarn nonwoven fabric which is suitable for an electrode separator for alkali secondary batteries and a padding cloth having a dry fabric hand with good balance of hydrophobic and hydrophilic properties by mixing a hydrophobic filament yarn obtained by subjecting to melt-flow spinning with a hydrophilic filament yarn. SOLUTION: A hydrophobic polymer with a surface tension of <=45dyne/cm such as a polyolefin, fluoropolymer or a polyester and a hydrophilic polymer with a surface tension of >=45dyne/cm such as a polyamide are melt-blown from a melt-blowing spinneret where the orifices for the hydrophobic polymer and those for the hydrophilic polymer are alternately arranged in a line to give the combined filament yarn nonwoven fabric with fluffs reduced, comprising 10-80wt.% of the hydrophobic fiber and 90-20wt.% of the hydrophilic fiber, having an average fiber diameter of 0.5-10μm and a unit weight (metsuke) of 5-100g/m<2> and a thickness of 0.1-1.5mm in at least one of the fibers. This nonwoven fabric is treated with a hydrophilizing agent in an amount of 0.1-3wt.% to give the objective combined filament yarn nonwoven fabric with a water retention of >=200%, water absorption rate of >=300mm/30min, alkali resistance of <=5%, and the water absorption rate of >=200mm/30min after 10min soaking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed fiber non-woven fabric composed of ultrafine fibers spun by a melt blow method, and more particularly to a mixed fiber non-woven fabric composed of hydrophobic fibers and hydrophilic fibers, which are different materials. By utilizing the characteristics of the above, it can be used as an alkaline secondary battery separator that has an excellent balance of chemical resistance and hydrophilicity with respect to aqueous chemicals centered on alkaline aqueous solutions, as well as an interlining material for clothes that has excellent moisture permeability and has a dry feel. The present invention relates to a suitable mixed fiber nonwoven fabric.

[0002]

2. Description of the Related Art Nonwoven fabrics obtained by the melt blow method have a large surface area, bulkiness, and
It is used in various applications such as filters, masks, wiping cloths, battery separators, clothing interlinings, and heat insulating materials by taking advantage of its characteristics such as shielding properties. For an example of using a meltblown nonwoven fabric made of polyamide as a battery separator, see [CONH / CH] in Japanese Patent Publication No. 5-64418.
₂ ratio] is 1/9 to 1/12 and the fiber diameter is 3 μm to 10 μ
m non-woven fabric is disclosed.

As a mixed fiber type melt-blowing method, Japanese Patent Application Laid-Open No. 60-99057 discloses a method for producing an ultrafine fiber nonwoven fabric in which two types of thermoplastic resins are combined in parallel and spun by the melt-blowing method. ing. In addition, JP-A-7-8
Japanese Patent No. 2649 discloses an ultrafine mixed fiber product composed of a high melting point component and a low melting point component having a melting point difference of 10 ° C. or more, and a manufacturing method. Further, Japanese Patent Laid-Open No. 7-102408 discloses a melt blow spinneret device as a manufacturing method. These mixed fiber type non-woven fabrics have low adhesive strength between fibers and are subjected to a fusion treatment by post-processing such as calendering to improve the dimensional stability of the non-woven fabric.

[0004]

The conventional non-woven fabric composed of ultrafine fibers has a drawback in that the structure is not stabilized mainly by the entanglement and fusion of the fibers, so that the strength is weak and fuzzing is large. It was unsuitable for clothing interlinings that had problems of process passability and required abrasion resistance and washing resistance. As a method for enhancing the low structural stability of such a non-woven fabric, measures such as heat treatment using a heating press roller or an ultrasonic welder have been adopted. However, the number of processes increases and the cost increases,
In some cases, the fibers of the bonded portion melted and the non-woven fabric became a film, which deteriorated the texture.

Conventionally, as a polymer to be used for a melt blown nonwoven fabric, most of the materials have been polypropylene because of its high productivity, easy miniaturization and chemical resistance. However, post-processing is required for battery separator applications that require hydrophilicity, and the sustainability of the effect was not sufficient.

[0006] Nylon meltblown non-woven fabrics are excellent in hydrophilicity, but they tend to be fluffed and easily cause problems in sheet handling. Particularly in alkaline secondary batteries and the like, where durability in an alkaline aqueous solution is important, there is a problem that the nonwoven fabric is oxidized and the shape cannot be retained.

As a means for solving these problems, it is possible to mix fibers having different fiber characteristics, but there is a problem that fibers having a large difference in surface tension are difficult to fuse with each other and the dimensional stability is not good. It was Further, there is no known method for uniformly mixing different kinds of fibers.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and are composed of a hydrophobic fiber and a hydrophilic fiber, which are suitable for battery separators, clothing interlinings, heat insulating materials and the like. The present invention has led to the invention of a mixed fiber non-woven fabric excellent in lint-free property in which fibers hardly drop out and in which fibers are uniformly dispersed, and which is excellent in process passability. Hereinafter, the present invention will be described in detail.

In the first invention, hydrophobic fibers and hydrophilic fibers spun by the melt blow method are mixed with each other,
The surface tension of the polymer that constitutes each fiber is 45d.
less than yne / cm, 45 dyne / cm or more, the hydrophobic fiber is 10 to 80% by weight, and the hydrophilic fiber is 90 to
It is a mixed fiber non-woven fabric containing 20% by weight and having little fuzz.

In a second aspect of the invention, at least one of the fibers of the first aspect of the invention has an average fiber diameter of 0.5 μm or more.
0 μm or less, the weight of the entire nonwoven fabric is 5 g / m ² or more and 100 g / m ² or less, and the thickness of the nonwoven fabric is 0.1
It is a mixed fiber non-woven fabric having a size of at least mm and at most 1.5 mm.

The third invention is the mixed fiber non-woven fabric according to claim 1 or 2, wherein the hydrophobic fibers are made of polyolefin or a fluoropolymer, and the hydrophilic fibers are made of polyamide.

A fourth invention is the mixed fiber non-woven fabric according to claim 1 or 2, wherein the hydrophobic fibers are made of polyester and the hydrophilic fibers are made of polyamide.

A fifth aspect of the present invention is that the water retention of the mixed fiber non-woven fabric treated with 0.1 to 3% hydrophilicity is 200% or more, the water absorption rate is 30 mm / 30 minutes or more, and the alkali resistance is 5% or less, The mixed fiber nonwoven fabric according to any one of claims 1 to 4, which has a water absorption rate of 20 mm / 30 minutes or more after immersion in water for 10 minutes.

The present invention will be described in detail below.
The melt-blowing method, which is a method for producing a nonwoven fabric applied in the present invention, is a molten thermoplastic resin extruded from a spinning hole, is fiberized by a high-temperature and high-speed gas blown from around the spinning hole, or a collecting conveyor net or A method of spraying onto a rotating drum to obtain a fibrous web, disclosed in US Pat. No. 3,532,800.

In the method for producing a mixed fiber nonwoven fabric of the present invention, for example, a hydrophobic resin and a hydrophilic resin are fed into the spinneret by different extruders, and the discharge holes for the hydrophobic resin are alternated with the discharge holes for the hydrophilic resin. The molten polymer extruded from the spinneret lined up in (1) is manufactured by a melt blow method in which the molten polymer is thinned by a high-temperature high-speed fluid. As a result, the hydrophobic resin and the hydrophilic resin are thinned to a fiber diameter of 10 μm or less, and are taken up by a conveyor before the fibers are solidified, so that they are taken as a self-fused non-woven fabric having good dimensional stability. In order to self-fuse the fibers to stabilize the dimensions, the distance between the orifices is 1.5 mm or less and 0.4 mm or more, and the temperature of the fibers on the conveyor is higher than the glass transition temperature of at least one of the constituent resins. It is necessary. Further, when the sheet is pulled under the condition of being capable of self-fusing, fiber movement is suppressed because fusion occurs between adjacent fibers, it is difficult for the fibers to be ubiquitous, and it is possible to uniformly disperse the fibers. it can.
To determine whether the fibers are uniformly dispersed, the non-woven fabric is dyed, and the dispersion state can be grasped from the difference in dyeability due to the difference in material. In the mixed fiber nonwoven fabric of the present invention, the fibers were fine and the fibers were uniformly dispersed, so that the spots could not be visually confirmed.

When the hydrophobic resin and the hydrophilic resin are fed into the spinneret by independent extruders, the viscosity of each polymer can be adjusted and the discharge amount can be controlled separately. It is possible to control individual fiber diameters and constituent ratios of the hydrophilic fiber and the hydrophilic fiber. Thereby, the sheet characteristics of the mixed fiber nonwoven fabric can be controlled. As a result, the balance of contradictory characteristics such as dry feeling and water absorption can be controlled.

The surface tension of the polymer of the hydrophobic fiber used for producing the mixed fiber nonwoven fabric of the present invention is less than 45 dyne / cm, and the surface tension of the polymer of the hydrophilic fiber is 45 dyn.
e / cm or more. Although the reason why the critical value is 45 dyne / cm is not clear, various experiments have revealed that the difference in characteristics changes with this value. That is, the presence of fibers having a surface tension of less than 45 dyne / cm improves waterproofness and chemical resistance to water-based chemicals, for example, alkali resistance to KOH aqueous solution, which is important for battery separator applications. It is presumed that this is because the fibers do not get wet with the aqueous solution and are not easily eroded. On the other hand, the presence of fibers having a surface tension of 45 dyne / cm or more improves the properties such as moisture permeability and water absorption of the nonwoven fabric sheet. The surface tension is measured according to JIS K6768 in a standard solution (formamide 8 having a surface tension of 45 dyne / cm).
A cotton swab is dipped in a mixed solution of 0.3% by volume and 19.7% by volume of ethylene glycol monoethyl ether, the standard solution is applied on the film made of each polymer, and the state of the liquid film after 2 seconds is judged. The surface tension of the polymer that keeps the applied state for 2 seconds or more without breaking the liquid film is 45 dyne / cm or more, and the polymer that breaks the liquid film and generates droplets is 45 dyne.
/ Cm or less.

As the resin of the thermoplastic fiber used in the mixed fiber nonwoven fabric of the present invention, in the case of a hydrophobic resin, a polyolefin resin such as polyethylene, polypropylene and copolymer polypropylene, a polyester resin such as polyethylene terephthalate and polybutylene terephthalate, and a fluorine resin. Nylon 6 if it is a hydrophilic resin and hydrophilic resin,
Polyamide resin such as nylon 66, nylon 4, nylon 610.

The mixed fiber nonwoven fabric of the present invention contains 10 to 80% by weight, preferably 20 to 70% by weight, and more preferably 40 to 60% by weight of hydrophobic fibers in the mixed fibers. When the hydrophobic fiber content in the mixed fiber nonwoven fabric is less than 10% by weight, it becomes difficult to balance the characteristics of the hydrophobic fiber and the characteristics of the hydrophilic fiber. For example, taking a balance between waterproofness and hygroscopicity as an example, a nonwoven fabric having poor waterproofness is obtained. On the other hand, when the hydrophobic fiber content in the mixed fiber nonwoven fabric exceeds 80% by weight, the resulting nonwoven fabric has poor hygroscopicity.

In the mixed fiber nonwoven fabric of the present invention, the fiber diameter of at least one of the hydrophobic fiber and the hydrophilic fiber is 0.5.
It is not less than 10 μm and preferably not less than 1 μm and not more than 5 μm, more preferably not less than 1.5 μm and not more than 3 μm. When the fiber diameter of at least one of the fibers is less than 0.5 μm, the single yarn strength is low and fluffing is likely to occur, resulting in poor processability. Further, when the fiber diameter of both is more than 10 μm, the voids between the fibers become large, and when used as a battery separator, for example, a problem occurs in the electrolyte shielding property,
When used as a clothing interlining, there is a problem in the strike-back resistance, which is an adhesive passage. On the other hand, if the fiber diameters of both are smaller than 0.5 μm, the sheet tends to be fluffed, which causes a problem in handling.

The mixed fiber nonwoven fabric of the present invention has a basis weight of 5 g / m ^2.
Or more and 100 g / m ² or less, preferably 10 g / m ² or more and 50 g / m ² or less. If the basis weight deviates from this area, the combined functions cannot be realized. That is, when the basis weight is small and the sheet thickness is thin, the number of laminated fibers in the thickness direction is small, and it is difficult to express the fiber characteristics of both. Further, even if the basis weight is too large, improvement of the function cannot be expected. Explaining with an example, when it is used as a separator, if the basis weight is less than 5 g / m ² , a problem occurs in the shielding property of the electrolyte. When it is used as a clothing interlining, the smaller the basis weight, the better the compatibility with the outer material and the better the texture, and it is suitable as a thin and lightweight clothing interlining for women. However, if the basis weight is less than 5 g / m ² , a problem occurs in the anti-strikeback property.

The mixed fiber nonwoven fabric of the present invention has a thickness of 0.1 mm.
Or more and 1.5 mm or less, preferably 0.2 mm or more and 1.0
mm or less. For example, when the mixed fiber non-woven fabric of the present invention is used as a battery separator, if the thickness is less than 0.1 mm, not only the fiber filling rate becomes too large and the water retention rate deteriorates, but also the electrolytic solution shielding property is problematic. Cause If the thickness exceeds 1.5 mm, it is difficult to reduce the size of the battery, which is unsuitable. Further, when the mixed fiber non-woven fabric of the present invention is used for the clothing interlining, if the thickness is too small, the fiber filling rate becomes large and the water absorption and air permeability deteriorate. On the other hand, if the thickness is too large, there is a problem that the texture becomes hard.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION When the mixed fiber nonwoven fabric of the present invention is used as a battery separator, it is preferable to improve hydrophilicity by hydrophilic treatment. Generally, a polyoxyethylene-based hydrophilizing agent is often used as the hydrophilizing agent, but the hydrophilizing agent is not necessarily limited thereto. However, when used as a battery separator, a polyoxyethylene hydrophilizing agent is particularly useful. The amount of the hydrophilizing agent applied is preferably 0.1% by weight to 3% by weight based on the weight of the nonwoven fabric. If the applied amount is less than 0.1% by weight, the hydrophilic agent may not be uniformly applied to the nonwoven fabric, or the hydrophilicity may be insufficient. On the other hand, if the applied amount of the hydrophilizing agent exceeds 3% by weight, an excessive amount of the hydrophilizing agent is eluted into the liquid, which deteriorates the performance of the electrolytic solution when used as a separator, which is not preferable.

When the mixed fiber nonwoven fabric of the present invention is used as a battery separator for an alkaline secondary battery or the like, it is often subjected to a hydrophilic treatment, but the water retention rate is preferably 200% or more. If the water retention rate is less than 200%, the electrolytic solution cannot be sufficiently retained and the performance of the battery separator is deteriorated. There is no particular upper limit for the water retention rate, but it is desirable to be up to about 1000%.

The hydrophilized mixed fiber nonwoven fabric of the present invention has a water absorption rate of 30 mm / 30 minutes or more, preferably 50 mm /
30 minutes or more. When the mixed fiber non-woven fabric of the present invention having a water absorption rate of less than 30 mm / min is used as a battery separator, the mixed fiber non-woven fabric of the present invention is not compatible with the electrolytic solution and deteriorates the battery performance.

When the hydrophilized mixed fiber nonwoven fabric of the present invention is used as a battery separator, the alkali resistance is 5% or less, preferably 3% or less based on the weight of the nonwoven fabric. If the alkali resistance exceeds 5%, it becomes difficult to maintain the shape as a battery separator, and the sheet may dissolve into the liquid and cannot maintain the shape when used for a long time. There is also a problem that the performance of the battery is deteriorated due to deterioration of the electrolytic solution due to the eluted resin. The mixed fiber nonwoven fabric of the present invention is suitable as a battery separator because, for example, polypropylene improves the shape retention due to its good oxidation resistance and polyamide functions to suppress the decrease in hydrophilicity.

When the mixed fiber nonwoven fabric of the present invention is subjected to a hydrophilic treatment and used as a battery separator, the water absorption rate after immersion in water for 10 minutes is preferably 20 mm / 30 minutes or more. When the water absorption rate after immersion in water for 10 minutes is less than 20 mm / 30 minutes, the hydrophilizing agent of the battery separator is eluted, which causes deterioration of battery performance.

When the materials constituting the mixed fiber non-woven fabric are fluoropolymer and polyamide, when the non-woven fabric is triboelectrically charged by using a needle punch machine or the like, the electric charge is small and the performance as an electret filter is small. There is also an advantage that can be maintained for a long time. Further, since there are fibers having different polymer surface characteristics, there is an advantage that the performance is improved when used as a liquid filter for filtering suspended matters having different surface potentials.

[0029]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples. The physical properties shown in the examples were measured by the following methods.

B. Measurement of Fiber Diameter A scanning micrograph of the fiber was taken at a magnification of 1000 times, the width of the side surface of 500 fibers arbitrarily extracted from the photograph was measured, and the width was determined by the arithmetic mean.

B. Measurement of basis weight 5 sheets are cut out in a certain area and weighed by a precision balance. The measured value is the arithmetic mean, and the basis weight which was calculated per 1 m ^2.

C. Measurement of thickness A sample was cut into a sample with a width of 2 cm and a length of 10 cm
7 g according to SL 1096 (General textile property test method)
The average value was obtained by measuring with a load of / cm ² .

D. Water retention rate A sample is cut into a width of 10 cm and a length of 10 cm, and left as a pretreatment at 20 ° C. and a relative humidity of 65% for 24 hours or more. The sample is weighed with a precision balance, immersed in distilled water for 1 hour, cut into droplets for 10 minutes, placed in a known weight container, and weighed. The water retention rate was determined from the weight difference before and after the test.

E. Water absorption rate The sample is cut into a rectangular shape with a width of 2 cm and a length of 30 cm, and the sample is held so as to be vertical. The bottom of the sheet is 5 in distilled water
It was dipped in mm and the suction height after 30 minutes was determined.

F. Alkali resistance A sample is cut into a certain size and left as a pretreatment for 24 hours or more at 20 ° C. and 65% relative humidity. The sample is weighed with a precision balance and immersed in a boiling 31% KOH aqueous solution for 1 hour. After immersion, the sample is washed with distilled water and dried, then 20
The sample is allowed to stand for 24 hours or more at a temperature of 65 ° C. and a relative humidity of 65%, and the weight of the sample is weighed. The alkali resistance is evaluated from the weight change before and after the treatment.

Example 1 Using a melt-blowing spinneret in which polypropylene discharge holes having a MI of 60 with a hole diameter of 0.3 mm and nylon 6 discharge holes were alternately arranged in a row, the spinning temperature was 275 ° C., and MI was used.
The single-hole discharge rate of polypropylene of 60 is 0.10 g /
Min., The discharge rate of nylon 6 with a relative viscosity of 2.2 is 0.1
0 g / min, traction air temperature of 420 ° C., traction air pressure of 0.7 kg / cm ² were spun, and sprayed onto a conveyor net with a suction device, and the mixing ratio of polypropylene fiber and nylon 6 fiber was 50 /. 50 (weight) is basis weight 3
A 0.8 g / m ² mixed fiber nonwoven fabric was obtained. The obtained mixed fiber non-woven fabric was a non-fluffed non-woven fabric having good processability.
To improve the hydrophilicity of this mixed fiber non-woven fabric, 0.5% of Perex RP (manufactured by Kao), which is a polyoxyethylene-based hydrophilic agent, is used.
% Aqueous solution to impart a hydrophilizing agent. The characteristics of this non-woven fabric are shown in Table 1. The non-woven fabric satisfied all the required characteristics as a battery separator. In addition, when used as a clothing interlining, there was no problem with strike back, and the texture was excellent in water absorption and dry feeling.

Example 2 Using the melt-blowing spinneret used in Example 1, the spinning temperature was 275 ° C., polypropylene with MI of 300 had a single hole discharge rate of 0.15 g / min, and nylon 6 had a relative viscosity of 2.2. Single hole discharge rate of 0.10 g / min, traction air temperature 4
The mixture was spun under the conditions of 20 ° C. and a pulling air pressure of 0.7 kg / cm ² , and was sprayed on a conveyor net with a suction device, and the mixing ratio of polypropylene fiber and nylon 6 fiber was 60 /.
A mixed fiber nonwoven fabric having a basis weight of 31.4 g / m ² was obtained at 40 (weight). The obtained mixed fiber non-woven fabric was a non-fluffed non-woven fabric having good processability. This mixed fiber non-woven fabric was subjected to the same hydrophilic treatment as in the example in order to improve hydrophilicity. The non-woven fabric properties are also shown in Table 1. The non-woven fabric also satisfied all the required characteristics as a battery separator. In addition, when used as a clothing interlining, there was no problem of strike back, and the texture was excellent in water absorption and dry feeling.

Comparative Example 1 Using a melt-blowing spinneret in which discharge holes having a hole diameter of 0.3 mm are aligned, a spinning temperature of 275 ° C. and a relative viscosity of 2.
Single-hole discharge rate of nylon 6 of 2 is 0.15 g / min, traction air temperature is 420 ° C, traction air pressure is 1.1 kg / cm ²
The fiber was spun under the conditions described above and sprayed onto a conveyor net equipped with a suction device to obtain an ultrafine nylon 6 nonwoven fabric having a basis weight of 31.0 g / m ² . In this non-woven fabric, fibers were fused to each other and were free of fluff. This non-woven fabric was subjected to the same hydrophilic treatment as that of the example in order to improve hydrophilicity. The characteristics of this non-woven fabric are shown in Table 1. This non-woven fabric had an alkali resistance of 7% after hydrophilization, which caused a problem in use as an alkaline secondary battery separator.

Comparative Example 2 Using a melt-blowing spinneret in which discharge holes having a hole diameter of 0.3 mm are aligned, a spinning temperature of 260 ° C. and an MI of 500 are used.
The polypropylene single hole discharge rate is 0.15 g / min,
Traction air temperature 450 ℃, traction air pressure 0.9kg / cm
^The fiber was spun under the conditions of ² and sprayed on a conveyor net with a suction device to obtain an ultrafine polypropylene nonwoven fabric having a basis weight of 30.2 g / m ² . In this non-woven fabric, fibers were fused to each other and were free of fluff. The characteristics of this non-woven fabric are shown in Table 1. This non-woven fabric was poor in suction height and liquid retention and could not satisfy the required characteristics as a battery separator.

Comparative Example 3 Using the melt-blowing spinneret used in Example 1, the spinning temperature was 275 ° C., polypropylene with MI of 1000 had a single hole discharge rate of 0.05 g / min, and nylon 6 had a relative viscosity of 2.2. Single hole discharge rate of 0.2g / min, traction air temperature 4
Spinning was carried out under the conditions of 50 ° C. and a pulling air pressure of 1.5 kg / cm ² , and the mixture was sprayed on a conveyor net with a suction device, and the mixing ratio of polypropylene fiber and nylon 6 fiber was 20 /.
A mixed fiber nonwoven fabric having a basis weight of 30.4 g / m ² was obtained at 80 (weight). During the production of this mixed fiber non-woven fabric, fibers were frequently scattered, and the scattered fibers were mixed into the non-woven fabric, resulting in a non-woven fabric with a lot of fuzz. The non-woven fabric properties are shown in Table 1. As described above, this mixed fiber non-woven fabric is a non-woven fabric with a lot of fluff, and the process passability during post-processing was poor, and treatments such as hydrophilization and calendering were difficult.

[0041]

[Table 1]

[0042]

EFFECTS OF THE INVENTION The present invention is a mixed fiber non-woven fabric composed of hydrophobic fibers and hydrophilic fibers, which has a good balance of hydrophobicity and hydrophilicity derived from the material, and a dry feeling and water absorption property. It can be used for well-balanced clothing interlining. It is also preferable to use three or more kinds of polymers in combination.

Claims (5)

[Claims] 1. A hydrophobic fiber and a hydrophilic fiber, which are spun by the melt blow method, are mixed with each other, and the surface tension of the polymer constituting each fiber is 45 dyne /
cm, 45 dyne / cm or more, 10 to 80% by weight of the hydrophobic fibers and 90 to 20% by weight of the hydrophilic fibers, and a mixed fiber non-woven fabric with less fluffing. 2. The non-woven fabric according to claim 1, wherein at least one of the fibers has an average fiber diameter of 0.5 μm or more and 10 μm or less, and the weight of the entire nonwoven fabric is 5 g / m ² or more and 100 g / m.
² or less, and the thickness of the nonwoven fabric is 0.1 mm or more
A mixed fiber non-woven fabric having a size of 5 mm or less. 3. The mixed fiber non-woven fabric according to claim 1, wherein the hydrophobic fiber is made of polyolefin or a fluoropolymer, and the hydrophilic fiber is made of polyamide. 4. The hydrophobic fiber is made of polyester, and the hydrophilic fiber is made of polyamide.
The mixed fiber non-woven fabric described in. 5. The water retention rate of the mixed fiber nonwoven fabric treated with 0.1 to 3% hydrophilicity is 200% or more, and the water absorption rate is 30 mm /
30 minutes or more, alkali resistance is 5% or less, 1
The mixed fiber nonwoven fabric according to any one of claims 1, 2, 3, and 4, which has a water absorption rate of 20 mm / 30 minutes or more after being immersed in water for 0 minutes.