JPH1088476A - Superfine short fiber for papermaking and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide uniform superfine short fibers for papermaking having 1-10μm fiber diameter and 300-2000L/D, ratio of the length of the single fiber L over the diameter of the single fiber D, and a method for efficiently producing the same. SOLUTION: The superfine short fibers for papermaking are produced by putting composite short fibers, obtained by cutting the composite fibers consisting of an easily alkali-hydrolyzable polymer (polymer A) and at least one component or more of polymers (polymer B) being differently hydrolyzable from the easily alkali-hydrolyzable polymer into <=5mm length, in a bag of a non alkali hydrolyzable fiber, dipping the bag into an aqueous alkali solution having >=3 times weight of the composite short fiber and decomposing and removing the easily alkali-hydrolyzable polymer component (polymer A) by exposing in a mild flowing condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a fiber having a single yarn diameter of 1 to 10 μm and a ratio of a single yarn diameter [D] to a length [L];
The present invention relates to a uniform ultrafine short fiber for papermaking having an L / D of 300 to 2,000 and a method for producing the same.

[0002]

2. Description of the Related Art As a method of taking out a bundle of ultrafine fibers by decomposing and removing one component from a conjugate fiber, for example, a tow of the conjugate fiber is preliminarily shrinked, and a sea component of the conjugate fiber is removed with an organic solvent. (Japanese Patent Publication No. 54-28490), wrapping a composite fiber around a non-alkali hydrolyzable porous bobbin, circulating an alkaline solution using a cheese dyeing machine, etc. Of dissolving and removing conductive resin to obtain a bundle of ultrafine fibers (Japanese Patent Application Laid-Open No. 4-65577)
Etc. are known.

[0003] As a method for producing ultrafine short fibers for papermaking, a method of obtaining ultrafine short fibers by dispersing short fibers of polyester ultrafine fiber-generating fibers in water and subjecting the fibers to beating treatment (Japanese Patent Application Laid-Open No. 4-100992); A method in which a conjugate fiber is treated with an alkaline solution and then beaten to obtain a polyester synthetic pulp (JP-A-56-165012). Dissolve polyester and / or
Alternatively, a method of obtaining a pulp-like substance having substantially no branching by decomposing and removing (JP-A-7-331581) is known.

[0004]

Various methods for producing ultrafine short fibers for papermaking have been proposed, but ultrafine fibers having a fiber diameter of 10 μm or less may be fused when cut into short fibers, or the ultrafine short fibers may be bonded to each other. Slurry clumps are generated because they are easily entangled. Therefore, it is very difficult to obtain ultrafine short fibers for papermaking that can be uniformly dispersed, and it has not been achieved yet. For example, as disclosed in the above-mentioned two patent documents, there is a method in which an ultrafine fiber bundle obtained by dissolving and removing a specific component from a conjugate fiber in a bundle state is cut into short fibers by a cutter or the like. In this method, when the obtained bundle of ultrafine fibers is cut into short fibers, cut binding occurs when the diameter of the ultrafine fibers is reduced. As a result, when dispersed in water, the cut binding surface does not disperse and short fiber clumps are formed, and a good ultrafine short fiber sheet cannot be obtained.

On the other hand, as disclosed in the above-mentioned two patent documents, release-type conjugate short fibers that have been cut short beforehand are dispersed in water, beaten with a pulper, beater, refiner, or the like, and subjected to ultrafine processing. A method for obtaining short fibers, and an alkali treatment of cut fibers of a weight-reduced conjugate fiber composed of a linear aromatic polyester and a special alkali-soluble organic compound by an immersion method, followed by a similar beating treatment in water to produce an ultrafine fiber. In the method for obtaining short fibers, a fibrillated pulp can be obtained. Therefore, entanglement of the ultrafine short fibers occurs due to the fibrillated product. Further, since it is a pulp-like material, the obtained ultrafine short fibers have various fiber diameters and fiber lengths. In these methods, it is not possible to obtain ultrafine short fibers for papermaking having a uniform fiber diameter and a uniform fiber length such that the single yarn is uniformly dispersed in water.

[0006] As disclosed in the above-mentioned last patent document, sea-island fibers containing melt-anisotropic aromatic polyester as island components are cut into short fibers, and then the alkali-reducible polyester components are immersed in a immersion method. In the method of dissolving and / or decomposing and removing to obtain a pulp-like product, the obtained pulp-like product has a single yarn diameter distribution of 0.1 to 0.1, although there is substantially no branching.
It is as large as 4 μm, and a single yarn having a small diameter is entangled. In addition, when the above-mentioned conjugate short fibers are directly subjected to alkali weight reduction processing by an immersion method, since the generated ultrafine short fibers are violently stirred in a high-temperature alkaline aqueous solution, problems such as complicated intertwining of the ultrafine short fibers occur. I do. Therefore, according to this method, it is not possible to obtain a fine ultrafine short fiber for papermaking having a uniform single yarn diameter and L / D and being uniformly dispersed in water.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the single yarn diameter of the fiber is 1 to 10 μm, and the ratio of the diameter [D] of the single yarn to the length [L], L / D is 300-200
The present invention was found to be uniform and extremely thin for papermaking, and a simple method for producing the same. The present invention relates to a non-alkali hydrolyzable composite staple fiber comprising an alkali hydrolyzable polymer (polymer A) and at least one polymer (polymer B) having a different hydrolyzability from the alkali hydrolyzable polymer. A fiber having a single yarn diameter of 1 to 10 μm, obtained by decomposing and removing an alkali-hydrolysable polymer component while exposing the bag and / or the aqueous alkali solution to a fluidized state. The ratio of the diameter [D] to the length [L] of the yarn, L / D is 300-2
It is characterized by a uniform ultrafine short fiber for papermaking of 000.

A composite fiber comprising an alkali-hydrolysable polymer (polymer A) and at least one polymer (polymer B) having a different hydrolyzability from the alkali-hydrolysable polymer is reduced to a length of 5 mm or less. The cut composite staple fiber is sealed in a bag made of non-alkali hydrolyzable fiber, immersed in an alkaline aqueous solution having a weight of at least three times the weight of the composite staple fiber, and the bag and / or the alkaline aqueous solution is allowed to flow. A fiber having a diameter of 1 to 10 μm, a diameter [D] of the single yarn and a length of 1 to 10 μm, wherein the alkali component hydrolyzable polymer component (polymer A) is decomposed and removed while being exposed to water.
[L] and L / D of 300 to 2,000.

According to this production method, under a condition of mild alkali weight loss, a uniform fiber diameter and L
Since the ultrafine short fibers for papermaking having / D are obtained, when the ultrafine short fibers are dispersed in water, a slurry without a uniform fiber mass can be easily obtained by ordinary stirring. Therefore, in order to uniformly disperse the pulp-like material in water, there is no need for a commonly used pulper, beater or refiner,
The ultrafine short fiber of the present invention can be suitably used for a nonwoven fabric sheet for artificial leather, a battery separator, and the like in which a fiber mass is a product defect. Moreover, since the ultrafine short fibers of the present invention have a uniform single yarn diameter and L / D, uniform three-dimensional entanglement treatment can be achieved by forming the obtained sheet into a nonwoven fabric by a method such as columnar flow entanglement. And an unexpectedly excellent effect such that a high-strength nonwoven fabric can be obtained.

The ultrafine short fibers for papermaking of the present invention are substantially different from pulp-like short fibers in a fibrillated state in which substantially various fiber diameters and fiber lengths are mixed. It is an ultra-fine short fiber that has very little entanglement and hardly generates defective fiber lumps. The conjugate fiber used in the present invention is a conjugate fiber comprising an alkali-hydrolysable polymer (polymer A) and at least one polymer (polymer B) having a different hydrolyzability from the alkali-hydrolysable polymer. The cross-sectional form of the fiber may be at least one selected from the group consisting of a laminated type, a split type, a wedge type, a core-sheath split type, and a sea-island type, and is not particularly limited. It is preferable that the polymer B to be the ultrafine fiber of the present invention is continuous in the length direction of the conjugate fiber and has a uniform fiber diameter.

For example, such an easily hydrolyzable polymer (Polymer A) is exemplified as a block polyether ester in which an alcohol component is copolymerized with polyethylene glycol having an average molecular weight of 600 to 6000, or sulfoisophthalic acid 2 as an acid component. It is a polyester copolymerized in an amount of at least mol% or a copolymerized polyester combining these two components. In particular, a block polyetherester obtained by copolymerizing polyethylene glycol in an amount of 10% by weight or more, preferably 15% by weight or more has an extremely large alkali dissolution rate constant K, and can be easily alkali-hydrolyzed under mild conditions (Polymer A). Is preferred because it can be decomposed and removed.

The alkali decomposition rate ratio between the alkali-hydrolysable polymer (polymer A) and at least one component (polymer B) having a different hydrolyzability from the alkali-hydrolysable polymer is preferably 1/100
It is 0 times or more, more preferably 1/1500 times or more. In addition, the alkali dissolution rate constant refers to a sample having a concentration of 2
It is a dissolution rate obtained by dissolving a 90% by weight aqueous solution of sodium hydroxide at 90 ° C. For calculating the alkali dissolution rate constant K of polyester fiber, see Hashimoto (Journal of the Textile Society of Japan,
14, 510.1958). That is, assuming that a fiber radius r ₀ (cm) of a polyester filament to be subjected to an alkali treatment before treatment and a treatment time until the filament completely dissolves and disappears are t (seconds), K = r ₀ / t (cm / second). ).

As the polymer B, for example, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and the like, and isophthalic acid, adipic acid, dodecandioic acid, sulfoisophthalic acid, cyclohexane dimethanol, etc. Modified polyesters obtained by copolymerizing acid components of the above or glycol components such as diethylene glycol, propylene glycol and polyethylene glycol, nylon 6, nylon 6, 6, nylon 12, poly-P-phenylene terephthalamide, poly-m-phenylene iso Examples include polyamides such as phthalamide, polyolefins such as polyethylene and polypropylene, and acrylics such as polyacrylonitrile.

The ultrafine short fibers for papermaking comprising the polymer B obtained by decomposing and removing the alkali-hydrolysable polymer (polymer A) from the conjugate fiber by the production method of the present invention include:
It is sufficient if the diameter of the single yarn of the fiber is ultrafine short fiber within the range of 1 to 10 μm, preferably within the range of 2 to 9 μm, and more preferably within the range of 2 to 7 μm. If it is less than 1 μm, entanglement of the ultrafine short fibers occurs, and it is not possible to obtain ultrafine short fibers for papermaking having good water single yarn dispersibility. Conversely, 10 μm
In such a case, the obtained fiber is hardly referred to as an ultrafine fiber, and a method of spinning by another method such as a direct spinning method is available at a lower cost.

The conjugate fiber used in the present invention comprises an alkali-hydrolyzable polymer (polymer A) and at least one polymer (polymer B) having a different hydrolyzability from the alkali-hydrolyzable polymer. The thickness of the single-fiber denier is usually in the range of 0.2 d to 10 d, preferably 0.3 d to 5 d.
It is about d. If the single yarn denier is less than 0.2 d, it will be difficult to stably spin the conjugate fiber. Conversely, if it exceeds 10d, many island components must be made in the conjugate fiber to reduce the fiber diameter of the ultrafine fiber obtained by decomposing and removing the alkali-hydrolysable polymer (polymer A). However, it is difficult to spin such a composite fiber.

The composition of the alkali-hydrolysable polymer (polymer A) in the conjugate fiber is 10 to 60
% By weight is preferred. When the proportion is less than 10% by weight,
It becomes difficult to form a form of ultrafine fiber that is continuous in the length direction of the conjugate fiber. On the other hand, if the proportion exceeds 60% by weight, the decomposed product of the easily hydrolyzable polymer (polymer A) extracted during the alkali weight reduction treatment frequently causes interfacial adhesion on the surface of the ultrafine short fiber. Surface adhesion between the ultrafine short fibers occurs, and the ultrafine short fibers for papermaking having good dispersibility of the single yarn in water cannot be obtained. Further, the spinning yield is remarkably deteriorated due to the fact that the yarn is easily bent at the time of spinning, the water content is difficult to adjust, the fluff is likely to occur, and the yarn is easily broken at the time of stretching or winding. In addition, at least one polymer having a different hydrolyzability from the alkali-hydrolysable polymer is used.
When the polymer (Polymer B) is a polyester, the transesterification reaction is likely to occur during spinning, so that problems such as a decrease in the weather resistance of the ultrafine short fiber obtained after the alkali weight loss tends to occur.

The above-mentioned conjugate fiber is converted to a conjugate short fiber having a fiber length of 1.0 mm to 5.0 mm, more preferably 2.0 mm to 3.0 mm, using a cutter such as a rotary cutter, a guillotine cutter and a cutter. Cut it. When the cut length is less than 1.0 mm, the composite short fibers and / or ultra-fine short fibers fall out of the bag made of the non-alkali hydrolyzable fiber during the alkali weight reduction processing of the alkali-hydrolyzable polymer (polymer A). I will. Further, when the obtained ultrafine short fibers are formed into a sheet, the entanglement between the ultrafine short fibers is so small that sufficient strength cannot be obtained. On the other hand, if the cut length exceeds 5.0 mm, the ultrafine short fibers obtained after the alkali weight reduction tends to become entangled, and the dispersibility of the single yarn in water deteriorates.

Subsequently, the conjugate short fibers are sealed in a non-alkali hydrolyzable bag. The non-alkali hydrolysable bag referred to here is a bag made of non-alkali hydrolyzable fibers such as polyamide fiber, polyolefin fiber, or acrylic fiber. The non-alkali hydrolyzable fiber may be in the form of a woven or knitted fabric. In the case of a woven fabric, its woven structure can be freely selected from plain weave, oblique weave, and satin weave as long as it satisfies the opening ratio described below. In the case of a knit, the knit structure can be freely selected from a flat knit, a tricot and the like as long as the knitting structure satisfies the opening ratio described later.

The non-alkali hydrolyzable bag used in the present invention has an opening ratio (an area of an opening portion per unit area) of 5% to 20%, preferably 5% to 15%. is there. When the opening ratio is less than 5%, the replacement of the amount of the alkali solution in contact with the conjugate short fibers is not sufficiently performed, resulting in non-uniformity. Conversely, if the opening ratio exceeds 20%, the composite short fibers and / or ultra-fine short fibers fall out of the bag made of non-alkali hydrolyzable fibers during alkali weight reduction processing of the alkali-hydrolyzable polymer (polymer A). Would.

As a result of various studies on a method of reducing alkali without enclosing the conjugate short fibers in a non-alkali hydrolysable bag, entanglement of ultra-fine short fibers occurred during the weight reduction processing due to the flow of the aqueous alkali solution circulating in the reactor. Was found to work. In particular, when a reactor that rotates under the condition of a small bath ratio is used, the ultrafine short fibers during the weight reduction are rubbed in the vessel wall portion of the reactor, and a tightly entangled cocoon-shaped fiber mass is formed. Even if the fiber mass in the cocoon state is beaten with a pulper, a refiner, a beater, or the like, the entanglement of the ultrafine short fibers in the fiber mass cannot be unwound, so that good dispersibility of the single yarn in water cannot be obtained.

In the present invention, it is necessary to enclose the composite staple fiber in a non-alkali hydrolyzable bag and to decompose and remove the alkali hydrolyzable polymer (polymer A) from the composite staple fiber. That is, by enclosing the composite staple fiber in a non-alkali hydrolysable bag, during alkali weight loss, the movement of the composite staple fiber and the ultrafine staple fiber is restricted to a certain extent, and entanglement between the ultrafine staple fibers is suppressed No fiber lump is generated when dispersed in water. Therefore, even if the composite short fibers are encapsulated in the non-alkali hydrolyzable bag, if the bag is made to flow violently,
The effect of enclosing the bag is lost, the ultrafine short fibers are easily entangled, and there is a possibility that a fiber mass is generated. Therefore, it is preferable that the flow of the alkaline aqueous solution (liquid circulation by rotation of the reactor, forced liquid circulation by a circulation pump, etc.) is also performed under mild conditions.

That is, it is preferable to realize a fluid state in which the fibers in the bag move gently and the alkaline aqueous solution is gently replaced. For the reasons described above, it has been found that a method of enclosing composite short fibers in a non-alkali hydrolysable bag is effective in the case of alkali weight reduction processing of composite short fibers in order to prevent fiber lump. The facility for producing ultrafine short fibers for papermaking of the present invention must be a facility capable of exposing the bag and / or the aqueous alkali solution to a fluidized state in a non-alkali hydrolysable bag enclosing an alkaline aqueous solution and composite short fibers. Must. Examples of equipment that can be exposed to the fluidized state include a rotating drum dyeing machine (indicated in FIG. 1), a miller dyeing machine, a rotating autoclave dyeing machine having a rotating mechanism, an earth pot, and a cheese dyeing machine. Among them, preferred equipment is a rotating drum dyeing machine, a Milner dyeing machine, and a rotating autoclave dyeing machine. Further preferred equipment is a rotary drum dyeing machine.

The non-alkali hydrolysable bag and / or
Alternatively, the first method of exposing the alkaline aqueous solution to a fluid state is a method in which a non-alkali hydrolyzable bag is fixed and the alkaline aqueous solution is caused to flow, for example, in a cheese dyeing machine or a drum dyeing machine or a dyeing tank of a Milner dyeing machine. This is a method in which a non-alkali hydrolysable bag in which conjugate short fibers are sealed and an aqueous alkali solution are charged, and the bag is not moved, and only the aqueous alkali solution is circulated in a liquid stream to carry out hydrolysis. Further, the second method is a method in which a non-alkali hydrolyzable bag and an alkaline aqueous solution are caused to flow together in a reaction vessel. For example, a non-alkali hydrolyzable bag placed in a reaction vessel of a rotary autoclave dyeing machine and an earth pot is used. A method in which a bag and an alkaline aqueous solution are caused to flow by rotation of a reaction tank, or a non-alkali hydrolysable bag is rotated by rotating a non-alkali hydrolysable bag with or without circulating an alkaline aqueous solution with a rotating drum dyeing machine or a Milner dyeing machine. Thus, a method of flowing the bag and the alkaline solution can be considered. The second method, in which both the non-alkali hydrolysable bag and the alkaline aqueous solution flow, is more preferable than the first method, in which only one of them flows.

Further, conditions for exposing to a fluid state will be described. First, when the alkaline aqueous solution is circulated, the strength of the flowing state of the alkaline solution is determined by the total amount of the alkaline solution and the circulation flow rate. When the time during which the total amount of the alkaline aqueous solution in the reaction tank is replaced is obtained by dividing the total amount of the alkaline solution by the circulating flow rate per unit time, the replacement time of the total amount of the alkaline solution is 1
0 seconds or more, preferably 30 seconds or more, more preferably 6 seconds or more.
A fluid state such as 0 seconds or more is preferable. If the vigorous circulation is performed such that the replacement time is less than 10 seconds, the non-alkali hydrolysable bag will be in a dance-like state inside the reaction tank, which is likely to cause entanglement of the obtained ultrafine short fibers, which is not preferable. .

Next, conditions for exposing the non-alkali hydrolyzable bag and the alkali solution to a fluid state by rotating the reaction tank will be described. The rotation direction may be rotated only in the same direction, but may be reversed. In addition, although continuous rotation or intermittent rotation is possible, it is more preferable to rotate the reaction tank intermittently when mild flow conditions are taken in order to suppress entanglement of the ultrafine fibers. At that time, intermittent rotation of 50% or less, preferably 30% or less, more preferably 20% or less of the total reaction time is preferable because the flow state of the present invention can be set mildly. Further, the interval of the intermittent rotation can be appropriately selected, and may be periodic or non-periodic. Next, the rotation speed (peripheral speed) of the reaction tank is preferably in the range of 0 to 50 m / min. More preferably, the peripheral speed is in the range of 1 to 40 m / min, and still more preferably in the range of 2 to 30 m / min. 5
When the vigorous rotation of 0 m / min or more is performed, the non-alkali hydrolyzable bag inside the reaction layer is in a danced state, and the ultrafine short fibers are easily entangled with each other, which is not preferable.

The condition of the fluidized state in the present invention can be selected by appropriately combining the above-described conditions for circulating an aqueous alkali solution and the conditions for rotating the reaction tank. Preferred embodiments of the present invention include, for example, When fixing the non-alkali hydrolysable bag with a cheese dyeing machine, a Milner dyeing machine, or a rotating drum dyeing machine and exposing it to a fluidized state by circulating an alkaline aqueous solution, the replacement time of the entire alkaline aqueous solution is circulated for 20 seconds or more. The flow rate and the like may be set. As a further preferred embodiment, when a non-alkali hydrolysable bag and an alkaline aqueous solution are put into a reaction tank by a rotary drum dyeing machine or a Milner dyeing machine and the reaction tank is rotated to be exposed to a fluidized state, the rotation speed (peripheral speed) Can be set in the range of 1 to 50 m / min. In this case, it is more preferable to take an intermittent rotation condition of 50% or less of the total reaction time, rather than to rotate continuously. Further, as a preferred embodiment, when exposing to a fluidized state by rotating the reaction tank with the rotary drum dyeing machine or the Milner dyeing machine and circulating the alkaline aqueous solution, the replacement time of the alkaline aqueous solution is set to 20 seconds or more. And set the rotation speed (peripheral speed) of the reaction tank to 1.
Intermittent rotation of 50% or less of the total reaction time at で 50 m / min can be selected.

Examples of the aqueous alkaline solution include strong alkaline aqueous solutions such as sodium hydroxide, potassium hydroxide, and trisodium phosphate. More preferably, it is an aqueous solution of sodium hydroxide. The concentration of the aqueous alkali solution varies depending on the temperature and time of the alkali weight reduction treatment, but at least one component that differs in the solubility of the easily hydrolyzable polymer (polymer A) and the hydrolyzability from the easily hydrolyzable polymer. In consideration of the erodibility of the polymer (Polymer B), it can be selected in the range of 1 to 10% by weight, more preferably 2 to 5% by weight. It is also possible to use a weak alkaline substance such as sodium carbonate, sodium silicate, sodium dihydrogen phosphate and the like in combination.

In addition, it is effective to add an anionic surfactant (for example, "Silicerol CAP" (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) for the purpose of increasing the alkali permeability of the conjugate fiber. . The treatment temperature of the alkaline aqueous solution is in the range of 70 to 130 ° C. Considering the damage of the obtained ultrafine short fibers, the temperature is more preferably in the range of 80 to 110 ° C. If the treatment temperature of the aqueous solution is lower than 70 ° C., the time required for the alkali weight reduction processing becomes longer, and if the temperature exceeds 100 ° C., an autoclave equipment having a pressure-resistant mechanism is required. The alkali weight loss time is 20 minutes to 120 minutes. In consideration of the damage of the obtained ultrafine short fibers and the cost merit of processing, it is more preferably 20 minutes to 90 minutes. When the alkali weight loss time is less than 20 minutes, a part where the alkali weight loss is incomplete remains. Conversely, if the alkali weight loss time exceeds 120 minutes, the resulting ultrafine short fibers become severely damaged.

The bath ratio between the conjugate short fibers and the aqueous alkali solution is at least 3 times, preferably at least 5 times, more preferably at least 10 times by weight. Further, it is more preferable that the alkaline aqueous solution inside the reaction layer is forcibly sucked and press-circulated using a pump. When the bath ratio is less than three times, the amount of the alkaline aqueous solution that comes into contact with the surface of the composite staple fiber decreases, so that the alkali reduction treatment cannot be performed uniformly. Further, when the bath ratio is 20 times or more, the amount of the alkaline aqueous solution used for the processing increases, so that the cost merit of the processing is diminished in consideration of the wastewater treatment or the like. In the method for producing ultrafine short fibers of the present invention, even when the bath ratio is extremely small as compared with the alkali weight reduction treatment by the conventional immersion method, uniform weight loss is achieved without causing partial weight loss spots. There is a feature. However, if the alkali concentration, temperature, etc., of the conjugate fiber are inappropriate and the weight is absolutely insufficient, the ultrafine short fiber for papermaking which is the object of the present invention and which does not generate fiber clumps cannot be obtained.

The ultra-short fibers obtained by reducing the alkali by the above method are subjected to an acid neutralization treatment using an organic acid such as acetic acid or oxalic acid, followed by washing with hot water or water, followed by dehydration treatment. Is more preferred. In addition, although a drying treatment may be performed, the dispersibility of the single yarn of the obtained ultrafine short fiber is slightly reduced. Evaluation of the dispersibility of the single yarns of the obtained ultrafine short fibers was performed at room temperature at room temperature by using ultrafine short fibers containing water (corresponding to 80% by dry weight) and 20% by weight of polyamide heat-fused fibers (2d × 1).
0 mm, "Unimelt UL60" manufactured by Unitika Ltd. Core part: nylon 6, sheath part: copolymerized nylon, core / sheath = 2 /
1) is dispersed in water, a 1% concentration slurry liquid is prepared, and the mixture is uniformly stirred with a stirring blade.
The sheet was collected as a sheet having a basis weight of 30 g / m ² and a width of 0.35 m × length of 1.0 m. Subsequently, a heat treatment (160 ° C.) was performed to fuse the sheath portion (copolymerized nylon) of the heat-fused yarn in the papermaking sheet, thereby preparing a single yarn dispersibility evaluation sample.

The dispersibility of the single yarn is as follows. Visual judgment focusing on the converging yarn and the binding yarn on the evaluation sample surface, and 2).
The evaluation was made by observing the variation of the diameter of the single yarn of the ultra-fine short fiber and the degree of dispersion of each single yarn by observation with an electron microscope photograph. Evaluation of the fiber mass of the obtained ultra-short fibers was conducted by dispersing ultra-short fibers containing water (100% by weight) in water at room temperature, preparing a 1% -concentration slurry solution, and uniformly stirring with a stirring blade. An inclined type fourdrinier machine with a basis weight of 30 g / m ² and a width of 0.
It was collected as a 35 m × 4.7 m length papermaking sheet. The number of fiber lumps having a diameter of 2 mm or more present in the papermaking sheet was counted, and the value converted to the number of fiber lumps per 1 m ² was defined as a fiber lump evaluation value.

The ultrafine short fibers for papermaking produced by the method of the present invention were evaluated for single yarn dispersibility using an electron microscope. As a result, the diameter of the single yarn of the ultrafine short fibers and the cross-sectional shape thereof were uniform. It was confirmed that there was no converged or bound ultra-fine short fiber. In addition, as a result of counting fiber lumps having a diameter of 2 mm or more, it was confirmed that fiber lumps were not substantially generated. Finally, the characteristics of the ultrafine short fibers for papermaking obtained by the method of the present invention are summarized as follows: 1) The diameter of the single yarn is in the range of 1 to 10 μm, preferably 2
2) The ratio of the diameter [D] to the length [L] of the single yarn, L / D is 30.
In the range of 0 to 2000, preferably in the range of 300 to 1500, and 3) has good dispersibility of single yarn in water, and 4) the fiber mass having a diameter of 2 mm or more is 1.5 Pcs / m ² or less, preferably 1.0 pcs / m ² , more preferably 0.5 pcs / m 2
^The ultrafine short fibers for papermaking, which are substantially free of fiber clumps, fall within the range of ² .

The term “uniform” as used herein means that the variation in the diameter and fiber length of a single yarn is small, and when expressed by the value of R, 50%
Or less, preferably 30% or less. That is, the ultrafine short fiber for papermaking of the present invention is clearly different from a pulp-like material in which the diameter and the fiber length of the single yarn vary. The ultrafine short fibers for papermaking obtained by the production method of the present invention have good single yarn dispersibility even when made alone, but are mixed with various organic synthetic fibers, natural fibers, glass fibers, inorganic fibers and the like. It is also possible to use. At that time, if necessary, a general pulper, beater, refiner or the like may be beaten. Specific applications include the field of high-performance industrial papermaking, for example, taking advantage of the dust-collecting properties of extra-fine yarns, commercial and household wipers, taking advantage of the covering properties of extra-fine yarns, medical applications, sanitary materials, liquids, Utilizing gas filters, speaker cones, packing materials, blanket wipers, strong confounding strength, and smoothness obtained from uniform ultra-fine short fibers, battery separators, synthetic leather base fabrics,
Coating base material, grain surface base material and the like can be mentioned.

In the field of artificial leather, for example,
It can be used in various fields such as women's clothing, gentlemen, women's shoes, bags, clothing accessories, golf gloves, furniture, car seats, and the like. For example, if the ultrafine short fiber obtained by the present production method is subjected to papermaking, columnar flow treatment, polyurethane application and used in the field of artificial leather, since the ultrafine single yarn is uniformly dispersed, the strength of the nonwoven fabric is excellent. , Surface nap is good,
A nubuck or suede surface with excellent nap density and an elegant lighting effect can be obtained. In addition, the product defect due to the fiber mass does not occur.

[0035]

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. [Method of measuring aperture ratio of woven or knitted fabric] Microscope (manufactured by MORITEX, SCOPEMAN MS803)
A magnified photograph of the woven or knitted fabric is taken at a measuring magnification of 50 times, the total weight of the photograph (A ₁ ) is measured, and the portion of the photograph where the fiber is shown is cut out with a cutter knife, and the weight of the remaining portion (A ₂₎ ) Is determined, and the value expressed as a percentage by dividing by the total weight (A ₁ ) is defined as the aperture ratio. [Aperture ratio (%)] = (A ₂ / A ₁ ) × 100

[Calculation method of processing bath ratio] The value obtained from the absolute dry weight (A ₁ ) of the composite staple fiber and the weight (A ₂ ) of the alkaline aqueous solution according to the following equation is defined as the bath ratio. The easy alkaline hydrolysis polymer [Measurement method of weight loss of the ultrafine short fibers] bath ratio = A ₂ / A ₁ absolute dry weight before (polymer A) to decompose and remove an alkaline aqueous solution (W _1), after the decomposition removal The value obtained from the absolute dry weight (W ₂ ) according to the following formula is defined as a weight loss rate (%). Weight loss rate (%) = [1− (W ₂ / W ₁ )] × 100

[Evaluation of Dispersibility of Single Yarn of Ultra-Fine Short Fiber] A visual judgment was made by focusing on the converging yarn and the binding yarn of the evaluation sheet. ○ Single yarns are uniformly dispersed. △ Converging yarns and binding yarns are present in some places. × Convergent yarns and binding yarns frequently occur. [Measurement of diameter of single yarn of ultra-fine short fiber] Scanning electron microscope (S-570, manufactured by Hitachi, Ltd., measurement magnification: 1000 to 30)
00), the diameter of the single yarn of the fiber randomly extracted is 10
The points were read and the average value was taken as the diameter of the single yarn.

Example 1 Polyethylene glycol was added to 1
5% by weight copolymerized block ether ester (hereinafter referred to as
3.0 d / f, where the copolymer component is a sea component and polyethylene terephthalate is 37 island components.
Sea-island fiber (0.05% after copolyester decomposition removal)
d / f, sea / island = 35% by weight / 65% by weight) was rewound to about 6000d, and then cut into 3mm sea-island short fibers using a rotary cutter.

2 kg each of the obtained sea-island staple fiber was dyed into a polypropylene bag (a 75d / 24f polypropylene fiber, a tricot knitted fabric designed to have an opening ratio of 15%). 12 bags are sealed, and the bag and a 4.5% by weight aqueous solution of sodium hydroxide 13
0 (liter) and 130 (cc) of an anionic surfactant (“Silicerol CAP” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.):
(Trade name) was placed in a drum tank of a drum dyeing machine.

The aqueous alkali solution in the reaction tank is reduced to 1 in about 4 minutes.
So that the drum tank portion is gently rotated at a peripheral speed of 10
(M / min) by intermittent rotation (repeating 10 seconds of rotation and 60 seconds of stop) to bring the bag containing the sea-island short fibers and the alkaline aqueous solution into a mild fluid state. The copolymerized polyester component was decomposed and removed under the conditions of an alkali weight reduction treatment temperature of 90 ° C. and a treatment time of 40 minutes, followed by repeating hot water washing three times, and finally performing centrifugal dehydration. The diameter of the single yarn of the obtained ultrafine polyester short fiber was substantially uniform, there was no portion where the ultrafine polyester short fiber converged, and the dispersion of the single yarn was good. The result of the fiber lump evaluation was a very good level without any fiber lump.

[Bath ratio] 5.4 [Weight loss rate] 35.5 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.20 (μm) [L / D] 1363 [Fiber lump] Number] 0.0 (pieces / m ² )

(Example 2) A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, the drum tank of the rotary drum dyeing machine was not rotated, and all other conditions were the same as in Example 1. In this state, the copolymerized polyester component was decomposed and removed. The diameter of the single yarn of the obtained ultrafine polyester short fiber was substantially uniform, and the dispersion of the single yarn was also substantially uniform. As a result of the evaluation of the fiber lump, the number of the fiber lump was at a satisfactory level without any practical problem.

[Bath ratio] 5.4 [Weight loss rate] 35.1 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.24 (μm) [L / D] 1338 [Fiber lump] Number] 0.4 (pieces / m ² )

Example 3 A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the drum tank of the rotary drum dyeing machine was continuously rotated at a gentle rotation condition at a peripheral speed of 10 m / min. The circulation of the alkaline aqueous solution by the circulation pump was stopped, and the copolymerized polyester component was decomposed and removed under the same flow conditions as in Example 1 under all other conditions. The diameter of the single yarn of the obtained ultrafine polyester short fiber was substantially uniform, and the dispersion of the single yarn was also substantially uniform. As a result of the evaluation of the fiber lump, the number of the fiber lump was at a satisfactory level without any practical problem.

[Bath ratio] 5.4 [Weight loss rate] 36.1 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.19 (μm) [L / D] 1372 [Fiber lump] Number] 0.3 (pcs / m ² )

Comparative Example 1 A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the circulation of the alkaline aqueous solution by the circulation pump was stopped without rotating the drum tank of the rotary drum dyeing machine. All other conditions were the same as in Example 1 to remove the copolyester component by decomposition. The dispersibility of the single yarn of the obtained ultrafine polyester short fiber was evaluated, and as a result of the fiber lump evaluation, the dispersion of the single yarn was good, but the conjugate short fiber in which the copolymer ester component remained unextracted was partially removed. Fiber mass was formed.

[Bath ratio] 5.4 [Weight loss rate] 32.3 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.32 (μm) [L / D] 1295 [Fiber lump] Number] 2.8 (pieces / m ² )

[0048]

[Table 1]

Example 4 A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the drum tank of the rotary drum dyeing machine was continuously rotated at a gentler rotating condition at a peripheral speed of 5 m / min. In all other conditions, the copolymerized polyester component was decomposed and removed in the same fluidized state as in Example 1. As a result of evaluating the dispersibility of the single yarn and the evaluation of the fiber lump of the obtained ultrafine polyester short fiber, the dispersion of the single yarn was good and the level was very good without any fiber lump. [Bath ratio] 5.4 [Weight loss rate] 35.6 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.20 (μm) [L / D] 1351 [Number of fiber mass] 0 0.0 (pieces / m ² )

Example 5 A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the drum tank of the rotary drum dyeing machine was continuously rotated at a gentle rotation condition at a peripheral speed of 10 m / min.
In all other conditions, the copolymerized polyester component was decomposed and removed in the same fluidized state as in Example 1. Dispersibility evaluation of single yarn of the obtained ultrafine polyester short fiber, the result of fiber lump evaluation,
And the dispersion of the single yarn was good. The number of fiber lumps was also at a good level without practical problems. [Bath ratio] 5.4 [Weight loss rate] 35.9 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.24 (μm) [L / D] 1342 [Number of fiber mass] 0 .6 (pieces / m ² )

Example 6 A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the drum tank of the rotary drum dyeing machine was continuously rotated at a gentle rotation condition at a peripheral speed of 23 m / min.
In all other conditions, the copolymerized polyester component was decomposed and removed in the same fluidized state as in Example 1. Dispersibility evaluation of single yarn of the obtained ultrafine polyester short fiber, the result of fiber lump evaluation,
And the dispersion of the single yarn was good. The number of fiber lumps was also at a good level without practical problems. [Bath ratio] 5.4 [Weight loss rate] 36.2 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.19 (μm) [L / D] 1371 [Number of fiber mass] 0 .8 (pieces / m ² )

(Example 7) A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the drum tank of the rotary drum dyeing machine was intermittently rotated under a gentle rotation condition at a peripheral speed of 23 m / min (rotation 10). For 2 seconds and stopping for 60 seconds), and the copolymerized polyester component was decomposed and removed under the same flow conditions as in Example 1 under all other conditions. The diameter of the single yarn of the obtained ultrafine polyester short fiber was almost uniform, and the dispersion of the single yarn was almost uniform and good. The number of fiber lumps was also at a good level without practical problems. [Bath ratio] 5.4 [weight loss rate] 35.7 (%) [Evaluation of dispersibility of single yarn] ○ [diameter of single yarn] 2.21 (μm) [L / D] 1355 [number of fiber mass] 0 .5 (pieces / m ² )

Comparative Example 2 A dyeing bag containing conjugate short fibers was prepared in the same manner as in Example 1, and the drum tank of the rotary drum dyeing machine was vigorously continuously rotated at a peripheral speed of 50 m / min. The copolymerized polyester component was decomposed and removed in the same fluidized state as in Example 1. As a result of the evaluation of the dispersibility of the single yarn of the obtained ultrafine polyester short fiber and the evaluation of the fiber lump, the single yarn of the ultrafine polyester short fiber was entangled, the fiber lump was frequently generated, and the dispersibility of the single yarn was remarkably deteriorated. [Bath ratio] 5.4 [Weight loss rate] 37.4 (%) [Evaluation of dispersibility of single yarn] × [Diameter of single yarn] 2.17 (μm) [L / D] 1383 [Number of fiber lumps] 5 .3 (pieces / m ² )

[0054]

[Table 2]

(Example 8) The same conjugate short fibers as in Example 1 were sealed in 4 bags of 2 kg each in the same dyeing bag as in Example 1, and the alkali concentration was shortened to 3.0% by weight and the alkali reduction time was shortened to 30 minutes. The copolymerized polyester component was decomposed and removed under the same flow conditions as in Example 1 under all other conditions. The dispersibility of the single yarn of the obtained ultrafine polyester short fiber was good, and was a very good level without any fiber mass. [Bath ratio] 16.3 [Weight loss rate] 35.3 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.25 (μm) [L / D] 1335 [Number of fiber mass] 0 0.0 (pieces / m ² )

(Comparative Example 3) The same conjugate staple fiber as in Example 1 was sealed in 30 bags of 2 kg each in the same dyeing bag as in Example 1; The components were decomposed and removed. As a result of evaluating the dispersibility of the single yarn of the obtained ultrafine polyester short fiber, a fiber bundle (bundle having a fiber length of 3 mm) in which extraction of the copolymerized polyester component was incomplete, branching due to rebinding on the surface of the short fiber Fiber lumps of the pulp-like material, twin slurries in which the fiber lumps were entangled, and the like frequently occurred. In addition, when the head of the twin slurry was cut in the cross-sectional direction with a razor blade, there was a portion where the weight was hardly reduced. [Bath ratio] 2.2 [Weight loss rate] 34.4 (%) [Evaluation of dispersibility of single yarn] × [Diameter of single yarn] 2.30 (μm) [L / D] 1304 [Number of fiber mass] 3 .2 (pieces / m ² )

[0057]

[Table 3]

Comparative Example 4 Twelve bags of the same sea-island staple fibers as in Example 1 were sealed in dyed bags of the same polypropylene fibers as in Example 1 with a tricot knitted fabric having an opening ratio of 25% and 2 kg each. The copolymerized polyester component was decomposed and removed in the same fluidized state as in Example 1. Almost 20 minutes after the start of the alkali weight loss, the ultra-fine polyester short fibers which received the alkali weight loss came out of the stitches of the dyeing bag, and the filter installed in front of the circulation pump in the liquid circulation line was clogged and rotated. The drum dyeing machine stopped automatically. Evaluation of dispersibility of single yarn and evaluation of fiber lump were not performed. [Bath ratio] 5.4

Example 9 The same sea-island staple fiber as in Example 1 was sealed in four bags of 0.2 kg each in the same dyeing bag as in Example 1, and the bag and a 4.5% by weight aqueous sodium hydroxide solution 4 (liter) were added. 4) Anionic surfactant (4 cc) is put into a rotary autoclave dyeing machine, and the rotary autoclave dyeing machine itself is continuously rotated at a gentle rotation condition at a peripheral speed of 7 m / min. I made it. The copolymerized polyester component was decomposed and removed under the conditions of an alkali weight loss treatment temperature of 90 ° C. and a treatment time of 40 minutes. After the alkali reduction, the stained bag was taken out, washed with hot water three times, and finally centrifuged and dehydrated.

The diameter of the single yarn of the obtained ultrafine polyester short fiber was substantially uniform, there was no portion where the ultrafine polyester short fiber converged, and the dispersion of the single yarn was good. The number of fiber lumps was also at a good level without practical problems. [Bath ratio] 5.0 [Weight loss rate] 35.3 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.23 (μm) [L / D] 1348 [Number of fiber mass] 0 .2 (pieces / m ² )

(Example 10) A block ether ester obtained by copolymerizing 10% by weight of polyethylene glycol was used as a sea component, and nylon 6 was used as 37 island components.
f sea-island fiber (0.0% after copolyester decomposition removal)
5 d / f, sea / island = 35 wt% / 65 wt%) tow was cut to a fiber length of 3 mm using a rotary cutter. The resulting sea-island staple fiber was sealed in the same dyeing bag as in Example 1 in four bags of 0.2 kg each. 5. Increase the alkali concentration to 6.
The copolyester component was decomposed and removed in the same fluidized state as in Example 9 except that the weight was 0% by weight, the alkali reduction treatment temperature was 105 ° C., and the treatment time was as short as 30 minutes.

The diameter of the single yarn of the obtained ultrafine nylon short fiber was substantially uniform, there was no portion where the ultrafine nylon short fiber converged, and the dispersion of the single yarn was good. As a result of the evaluation of the fiber lump, the number of the fiber lump was at a satisfactory level without any practical problem. [Bath ratio] 5.0 [Weight loss rate] 35.1 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.37 (μm) [L / D] 1264 [Number of fiber mass] 0 .3 (pieces / m ² )

(Example 11) A 2.0 d / f 20-split fiber in which a block ether ester obtained by copolymerizing 15% by weight of polyethylene glycol and polypropylene alternately exists (to 0.1 d / f after the copolyester is decomposed and removed). , Copolyester / polypropylene = 50% by weight
/ 50 wt%) was cut to a fiber length of 3 mm using a rotary cutter. The divided short fibers thus obtained were sealed in the same dyeing bag as in Example 1 in four bags of 0.2 kg each.
An alkali concentration of 3.0% by weight and an alkali weight loss time of 30
The copolymerized polyester component was decomposed and removed under the same flow conditions as in Example 9 under all other conditions.

As a result of evaluating the dispersibility of the single yarn of the obtained ultrafine polypropylene short fiber, the diameter of the single yarn was substantially uniform, there was no portion where the ultrafine polypropylene short fiber was converged, and the dispersion of the single yarn was good. Was. As a result of the evaluation of the fiber lump, the number of the fiber lump was at a satisfactory level without any practical problem. [Bath ratio] 5.0 [weight loss rate] 50.4 (%) [Evaluation of dispersibility of single yarn] ○ [diameter of single yarn] 4.00 (μm) [L / D] 750 [number of fiber mass] 0 .3 (pieces / m ² )

(Example 12) The same sea-island staple fiber as in Example 1 was sealed in the same dyeing bag as in Example 1 in 23 bags of 3 kg each.
The bag and a 4.5% by weight aqueous sodium hydroxide solution 300
(Liters), 300 (cc) of an anionic surfactant were placed in a cheese dyeing machine. While the alkaline aqueous solution was circulated by a circulation pump so that the alkaline aqueous solution in the reaction tank was replaced once in about 7 minutes, the bag containing the sea-island short fibers and the alkaline aqueous solution were brought into a mild fluid state. The copolymerized polyester component was decomposed and removed under the conditions of an alkali weight loss treatment temperature of 90 ° C. and a treatment time of 40 minutes.

Subsequently, after washing with hot water was repeated three times, the dyeing bag containing the ultrafine polyester short fiber was taken out of the cheese dyeing machine and finally centrifugally dewatered. The diameter of the single yarn of the obtained ultrafine polyester short fiber was substantially uniform, there was no portion where the ultrafine polyester short fiber converged, and the dispersion of the single yarn was good. As a result of the evaluation of the fiber lump, the number of the fiber lump was at a satisfactory level without any practical problem. [Bath ratio] 4.3 [Weight loss rate] 35.2 (%) [Evaluation of dispersibility of single yarn] ○ [Diameter of single yarn] 2.22 (μm) [L / D] 1353 [Number of fiber mass] 0 .8 (pieces / m ² )

[0067]

[Table 4]

Comparative Example 5 The same 0.8 kg of sea-island staple fiber as in Example 1 was not put in a dyeing bag, and the copolymerized polyester component was decomposed and removed under the same flow conditions as in Example 9 under all other conditions. After the alkali was reduced, the contents of the dyeing machine were transferred onto a nylon net, washed with hot water and centrifugally dehydrated. The obtained ultrafine polyester short fiber was in the form of a cocoon ball.
The cocoon balls were dispersed in water and stirred with stirring blades, but there were some that did not disentangle short fibers until the end.

The cocoon balls were beaten with a household mixer (MX-V350, manufactured by Matsushita Electric Industrial Co., Ltd.) for 2 minutes, but there was still a portion where the entanglement of ultrafine short fibers could not be unraveled. [Bath ratio] 5.0 [Weight loss rate] 36.6 (%) [Evaluation of dispersibility of single yarn] × [Diameter of single yarn] 2.26 (μm) [L / D] 1325 [Number of fiber mass] 6 0.0 (pieces / m ² )

[0070]

[Table 5]

Comparative Example 6 The same sea-island fiber as in Example 1 was wound around a porous acrylic bobbin and cut into a cheese dyeing machine without cutting into short fibers, and all other conditions were the same as in Example 12. The copolymerized polyester component was decomposed and removed in a fluidized state. After repeating the hot water washing three times, a bundle of ultrafine polyester fibers wound on an acrylic bobbin was taken out of the cheese dyeing machine without dehydration treatment. In the obtained bundle of ultrafine polyester fibers, the winding form partially collapsed, and there was a portion in which a single yarn was partially broken and in a fibril state. Subsequently, the bundle of ultrafine polyester fibers that had been wet was cut to a fiber length of 3 mm with a rotary cutter. However, single yarns of the ultrafine polyester fibers were partially broken, or fibrils in the guide portion of the rotary cutter were entangled. As a result, the rotary cutter could not be operated continuously.

Many of the obtained ultrafine polyester short fibers were fused in the cut section direction. A bundle of short fibers with a fiber length of 3 mm fused was dispersed in water, but the dispersion of single yarn was poor.
The bundle was 3 mm in fiber length. [Bath ratio] 4.3 [Weight loss rate] 35.5 (%) [Evaluation of dispersibility of single yarn] x [Diameter of single yarn] 5.67 (μm) [L / D] 529 [Number of fiber mass] 00 Pieces or more (pieces / m ² )

[0073]

[Table 6]

[0074]

The ultrafine short fibers obtained according to the present invention are:
Since it has a uniform fiber diameter and L / D, when it is dispersed in water, a uniform slurry without fiber lumps can be easily obtained by ordinary stirring, and the obtained paper sheet is nonwoven fabric by a method such as columnar flow entanglement. By doing so, uniform three-dimensional entanglement processing can be performed, and a high-strength nonwoven fabric can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a rotary drum dyeing machine in a facility for producing uniform ultrafine fibers for papermaking of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer body 2 Drum tank 3 Lid 4 Viewing window 5 Circulation pump 6 Heat exchanger 7 Drum rotation direction 8 Non-alkali hydrolysable bag containing compound short fiber 9 Alkaline aqueous solution

Claims (2)

[Claims] 1. A non-alkali hydrolyzed conjugate short fiber comprising an alkali-hydrolyzable polymer (polymer A) and at least one polymer (polymer B) having a different hydrolyzability from the alkali-hydrolyzable polymer. A single fiber diameter of 1 to 10 μm, obtained by decomposing and removing the easily hydrolysable polymer component while exposing the bag and / or the aqueous alkali solution to a fluidized state, And ultrafine short fibers for uniform papermaking, wherein the ratio of the diameter [D] to the length [L] of the single yarn and the L / D are 300 to 2,000. 2. A composite fiber comprising an alkali easily hydrolysable polymer (polymer A) and a polymer (polymer B) having at least one component having a different hydrolyzability from the alkali easily hydrolysable polymer, having a length of 5 mm or less. The composite staple fiber obtained by cutting into a bag is sealed in a bag made of non-alkali hydrolyzable fiber, immersed in an alkali aqueous solution having a weight of at least three times the weight of the composite staple fiber, and the bag and / or the alkaline aqueous solution is allowed to flow. The ratio of the diameter [D] of the single yarn to the length [L] of the single yarn of the fiber is 1 to 10 μm by decomposing and removing the easily hydrolyzable polymer component (polymer A) while being exposed to a state. And a method for producing uniform ultrafine short fibers for papermaking having an L / D of 300 to 2,000.