JP5275587B2 - Ultra-fine two-layer structure yarn and wiping cloth comprising the same - Google Patents

Description

  The present invention relates to an ultrafine two-layer structured yarn suitable for a wiping cloth having high water absorption, excellent wiping property and low dust generation, and a wiping cloth comprising the same.

  Conventionally, wiping cloths have been used for applications such as cleaning cloths, eyeglasses and lens wiping. And many of them have used natural fibers such as cotton fibers as fiber materials with good water absorption, and ultrafine fibers that are expected to increase the adsorption power by increasing the fiber surface area in the fabric. Today, wiping cloth is widely deployed in industrial fields such as IC and semiconductor manufacturing factories and clean rooms.

  As described in Patent Document 1 (Japanese Patent Laid-Open No. 61-228821), a wiping cloth in which a large amount of cellulose-based natural fibers are located on the surface of a fabric is used for wiping with oil, water, etc. Although the dust force is good, there is a problem that fluff falls on the surface of the object to be wiped and generates dust, and there are limits to industrial use such as IC and semiconductor manufacturing factories and clean rooms. Further, as described in Patent Document 2 (Japanese Patent Application Laid-Open No. 63-212364), high-density entanglement mainly composed of ultrafine yarns of 0.2 dtex or less and yarns of 0.5 to 10 dtex fibers. In woven and knitted fabrics, although wiping properties such as oil and water are good, the water jet punch is used to make the ultra-fine yarn and shrink, but the fiber cutting and strength are reduced. Due to the generation of dust, there were problems in the use of IC and semiconductor manufacturing factories and clean rooms.

Similarly, Japanese Patent Application Laid-Open No. 2004-8501 proposes an ultrafine fiber nonwoven fabric for wiping cloth. However, in order to make the separation split type composite fiber ultrafine by high pressure water flow treatment in the presence of water, Damage and cutting were inevitable, and there were problems of reduced strength and dust generation.
In view of these circumstances, there is a need for a wiping cloth material that captures and absorbs higher performance oil, moisture, dust, and the like.

Japanese Patent Laid-Open No. 61-228821 JP 63-2111364 A JP 2004-8501 A

  The present invention overcomes the above-mentioned problems, and has an ultra-fine two-layer structure yarn suitable for wiping cloth that has high wiping property for oil, water, etc., high dust trapping power, and can be used for industrial applications, and has little dusting property It is to provide a wiping cloth comprising the same.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to achieve the above object. That is, a double-layer structure yarn in which a multifilament A having a single yarn fineness of 0.001 to 0.01 dtex and a multifilament B having a single yarn fineness of 0.1 to 10 dtex are mixed, In the part, the number of places where the multifilament B appears on the fiber surface is 20 pieces / m or less, the multifilament A is mainly arranged in the sheath part, and the multifilament B is mainly arranged in the core part. Satisfactory ultra-thin bilayer yarn
(1) Strength of multifilament A ≧ 3.0 cN / dtex
(2) 20 / m ≦ entangled number of double-layer structure yarn ≦ 100 / m

  According to the present invention, by arranging the ultrafine fiber multifilament in the surface layer portion of the two-layer structure yarn, the sharp multi-shaving effect and the inner trap effect are exhibited, and the wiping property of oil, water, etc. Provided is a wiping cloth that can be used for industrial applications with high dust force and low dust generation.

The present invention is described in detail below.
Conventionally, many wiping cloths have used ultrafine fibers that are expected to increase the adsorptive power by increasing the fiber surface area in the fabric. The characteristics of the wiping cloth using ultrafine fibers are that water absorption and oil absorption increase due to the capillary phenomenon of the fiber gap, and that the sharp multi-shaving effect and inner trap effect peculiar to ultrafine fibers can be expected. On the other hand, since the fibers are thin, there is a problem that single yarn breaks and dust is generated.

  The present invention is a core-sheath type two-layer structure yarn in which a multifilament B having a large boiling water shrinkage is located in the core and a multifilament A is located in the sheath for the purpose of making use of the features of ultrafine fibers and preventing dust generation. The point is that it is used as a yarn for wiping cloth. After the wiped dirt is absorbed between the sheath fibers, the dirt is pushed up from the sheath to the core by the sharp multi-shaving effect, and the water absorption is improved by the capillary action and inner trap effect of the ultrafine fibers in the core. Increases wiping performance. INDUSTRIAL APPLICABILITY The present invention can provide a wiping cloth that has high wiping properties for oil, water, etc., has excellent dust capturing power, and can be used for industrial applications with little dust generation.

  Here, the sharp multi-shaving effect in the present invention is an effect utilizing a large surface area and a large number of fibers in a certain area. When the number of times of fiber contact with the object is much increased, the ultrafine fibers scrape the oil film and push it up to the upper superfine fiber group. When wiping with a thick fiber, the fat accumulated in the entire fiber due to the movement of the fiber is caught again under the fiber, and the removal function is inferior. The inner trap effect is an effect using a space (micro pocket) between ultrafine fibers. When the object is wiped off, the fiber group is pressed with the finger and the fat is sucked in. However, when the pressed state is released, the fat moves to the inside if the fiber density inside the fabric is high. The surface after movement has less fat and enhances the next wiping effect.

Single fineness multifilament A located in the outer layer portion of the wiping cloth of the present invention, Ri 0.001 Dtex～0.01Dtex der, preferably in the al, is in the range of 0.004~0.009dtex More preferred. When the single yarn fineness is 0.01 dtex or more, the performance of the wiping cloth such as water absorption and wiping properties is hindered. On the other hand, when the single yarn fineness is less than 0.001 dtex, the silk factor of the filament becomes small, which causes a problem in durability of the wiping cloth.

  The strength of the multifilament A needs to be 3.0 cN / dtex or more. If it is less than 3.0 cN / dtex, the strength is insufficient when a wiping cloth is used, and breakage or breakage is likely to occur. Preferably it is 4 cN / dtex or more.

  The sea-island composite fiber multifilament (hereinafter also referred to as “multifilament A ′”), which is used as the starting material for the multifilament A, is usually 10 to 50 dtex, preferably 20 to 40 dtex, and 5 to 5 filaments. 40 filaments, preferably 6-30 filaments.

  On the other hand, the multifilament B positioned at the core of the ultra-fine mixed yarn needs to have a single yarn fineness of 0.1 to 10 dtex. Preferably, it is in the range of 0.4 to 4 dtex. As the single yarn fineness becomes smaller than 0.1 dtex, the tension, waist and dimensional stability of the wiping cloth decrease. On the other hand, when it exceeds 10 dtex, it becomes hard and the wiping cloth performance decreases.

In order to obtain a core-sheath type two-layer structure yarn in which the multifilament B is located in the core and the multifilament A is located in the sheath, the following method is preferable.
That is, the core-sheath structure in which the multifilament A ′ and the multifilament B are aligned and entangled after the shrinkage difference in boiling water satisfies the following conditions and then contracted to arrange the multifilament A ′ in the sheath and the multifilament B in the core After forming the two-layer structure yarn, the sea component of the multifilament A ′ is dissolved and removed to make it ultrafine to obtain a core-sheath type ultrafine double-layer structure yarn having the multifilament A as the sheath and the multifilament B as the core. .
10% ≦ Δ boiling water shrinkage ≦ 40%
[Δ Boiling Water Shrinkage: Boiling Water Shrinkage of Multifilament B−Boiling Water Shrinkage of Multifilament A ′]

  The difference between the boiling water shrinkage of the multifilament B and the boiling water shrinkage of the multifilament A ′ [Δ boiling water shrinkage: the boiling water shrinkage of the multifilament B−the boiling water shrinkage of the multifilament A ′] is important, and 10% ≦ Δ boiling water It is necessary to set the shrinkage rate ≦ 40%. When the Δboiling water shrinkage rate is smaller than 10%, the multifilament B appears in the outer layer portion of the wiping cloth, and the wiping property is deteriorated. On the other hand, when the Δ boiling water shrinkage rate is larger than 40%, the texture becomes hard, which is not preferable as a product.

  The boiling water shrinkage of the multifilament A ′ is preferably 10% or less, preferably 0 to 8%, more preferably 1 to 5%. Furthermore, it is important that the boiling water shrinkage of the multifilament A ′ is 10 to 60% of that of the multifilament B. Preferably, it is 40 to 60% of range. If the boiling water shrinkage of multifilament A ′ exceeds 60% of multifilament B, it becomes difficult to form a core-sheath type two-layer structure yarn, and multifilament B appears in the outer layer portion of the wiping cloth, resulting in a decrease in wiping performance. It is not preferable. On the other hand, when the boiling water shrinkage ratio of the multifilament A ′ is less than 10% of the multifilament B, the texture becomes hard, which is not preferable as a product.

  Here, in order to set the boiling water shrinkage of multifilament A ′ to 10 to 60% of the boiling water shrinkage of multifilament B, the heat set temperature is controlled or the draw ratio is adjusted when drawing filament A ′. Then, the boiling water shrinkage rate may be adjusted.

  In the multi-filament A ′ sea-island type composite fiber, the larger the number of islands, the narrower the fiber composed of island components after sea dissolution, and the sharp multi-shaving effect and inner trap effect unique to ultra-fine fibers can be expected. It is important to be ~ 1,000 islands / single yarn. If it is less than 100 islands, the effect as an ultrafine fiber cannot be expected when the island ratio is small. On the other hand, if it exceeds 1,000 islands, not only the production cost of the spinneret increases, but also the processing accuracy itself tends to decrease. Preferably, it is 500 to 1,000 islands.

  The dissolution rate ratio of the sea component to the island component is preferably 30 to 5,000 times that of the island component. More preferably, it is 100 to 4,000 times. When the ratio is less than 30 times, a part of the separated island component of the fiber cross-section surface layer portion is dissolved, and the problem that the sea component at the center of the fiber cross-section is not dissolved easily occurs. Thereby, the thickness variation of an island component generate | occur | produces and it exists in the tendency for a problem to fall in a quality. On the other hand, if it exceeds 5,000 times, fiberization is difficult.

  As the polymer constituting the sea-island type composite fiber, the sea component polymer may be any fiber-forming polymer as long as the solvent dissolution rate difference with the island component is 30 times or more, such as polyamide, polystyrene, polyethylene, Any polymer such as polyester may be used. Of these, polyester is preferable for adjusting the solvent solubility. For example, in the case of an alkaline aqueous solution-soluble polymer such as potassium hydroxide or sodium hydroxide, polylactic acid, polyethylene glycol copolymer polyester, and copolymerized polyester of 5-sodium sulfonic acid isophthalic acid are optimal. Nylon 6 can be dissolved in formic acid, and polystyrene can be dissolved in an organic solvent such as toluene.

On the other hand, the island component polymer may be any fiber-forming polymer, and may be any polymer such as polyamide, polystyrene, polyethylene, or polyester. Polyester is preferable.
Furthermore, the shape of the island component is not limited to a round cross section, and may be an irregular cross section.

  The ratio of the sea component is preferably 5 to 40% of the total fiber weight in order to reduce the thickness of the sea component between the islands and to make a dense wiping cloth. More preferably, it is 10 to 30% of range. If it exceeds 40%, the thickness of the sea component becomes so thick that it is not preferable for separation of sea islands, and a precise wiping cloth cannot be formed. On the other hand, if it is less than 5%, the amount of polymer is too small, and it is difficult to uniformly distribute between a large number of islands.

  As a manufacturing method of multifilament A ', arbitrary things, such as what has a hollow pin group for forming an island component, and a fine hole group, can be used regarding the spinneret used for melt spinning. For example, a spinneret may be used in which an island component extruded from a hollow pin or a fine hole and a sea component flow that is designed to fill the gap between the island component are joined and compressed to form a cross section of the sea island. . Examples of spinnerets that are preferably used are shown in FIG. 2, but are not necessarily limited thereto. After being discharged by the above spinneret, it can be obtained by a normal melt spinning method.

  The multifilament B usually has a total fineness of 0.1 to 10 dtex, preferably 0.4 to 4 dtex, and a filament count of 12 to 168 filaments, preferably 24 to 144 filaments. As a method for producing the multifilament B, it can be obtained by a known melt spinning method.

Next, a preferred method for producing the mixed fiber described above will be described.
Unstretched multifilament A ′ is stretched by a conventionally known stretching method. Here, the temperature received by the yarn being drawn can be set by adjusting the heat treatment time, etc., depending on the type of the heating element, so if it can be adjusted, not only the contact type but also the non-contact type heating element Can be used.

  The multifilament A ′ after the drawing heat treatment is mixed with the multifilament B having a single yarn fineness of 0.1 dtex or more manufactured by a conventional method. A conventionally known method may be adopted as the fiber mixing method. For example, the multifilament A ′ and the multifilament B that have been heat-treated by drawing are aligned and supplied to an interlace nozzle with an overfeed of 1.0 to 1.5% to give entanglement and a two-layer structure yarn To do.

The obtained two-layer structure yarn is usually twisted in a twisting process, then knitted and woven, and processed in an ultrafine process.
The ultra-thinning process is generally performed by immersing and removing sea components in a solvent that dissolves the sea components alternately to elute and remove the sea components. When the sea component is polyester, it is preferable to remove the polyester with an alkali weight reduction device.

In the ultrathinning step, the multifilament A ′ constituting the blended yarn is ultrathinned to become a multifilament A which is a very fine fiber, and the multifilament B having a large boiling water shrinkage is cored by the thermal history. In the part, the multifilament A becomes a core-sheath type ultrafine two-layer structure yarn located in the sheath part. More specifically, the core-sheath type ultrafine two-layer sheath is composed of multifilament A having a single yarn fineness of 0.001 to 0.01 dtex, and the core portion is composed of multifilament B having a single yarn fineness of 0.1 to 10 dtex. A layered yarn is constructed.

The filament A appearing in the surface layer portion of the wiping cloth may have a round cross section or a modified cross section, and the sharper the knitting effect is, the better the wiping effect is.
Further, the wiping cloth may be any woven structure, and includes all weaves such as plain weave structure, satin weave structure, double weave of these, or changed structure. The knitted fabric may be either a circular knitting or a warp knitting structure.

  The weight ratio of the above-mentioned multifilament A and multifilament B constituting the wiping cloth of the present invention is 20:80 to 80:20, preferably 30:70 to 70:30. If the weight ratio of the multifilament A is less than 20% by weight, improvement in wiping performance cannot be expected. On the other hand, if it exceeds 80% by weight, the ratio of the multifilament A is too high compared to B, so that the woven fabric becomes crap.

Hereinafter, the present invention will be described in more detail by way of examples. The fabric was prepared as follows. Moreover, the measuring method was implemented as follows.
(1) Measurement of weight loss rate The yarn was wound at a spinning speed of 1,000 to 2,000 m / min with a 0.3φ-0.6L × 24H base of each of the sea and island polymers, and the residual elongation was 30. A 75 de / 24 fil multifilament was drawn by stretching to a range of ˜60%. The weight loss rate was calculated from the dissolution time and the dissolution amount at a bath ratio of 100 at a temperature at which the solvent was dissolved in each solvent.
(2) Boiling water shrinkage rate Using a measuring instrument with a frame circumference of 1.125m, make a small skein with 10 strikes, apply a weight of 20-50g, and set the initial skein length L0 (cm). It was measured. The weight was removed and immersed in warm water at 98 ° C. for 30 minutes, then taken out and allowed to dry naturally. After drying, the weight L1 (cm) after shrinkage was measured again by applying a weight. The above-described L0 and L1 were substituted into the following formula to calculate the boiling water shrinkage BWS (%).
BWS (%) = [(L0−L1) / L0] × 100
(3) Elongation Measured with a constant-speed elongation type. Elongation is expressed as elongation (%) at break.
(4) Evaluation method of wiping performance Artificial lipid was made to adhere to a glass plate, and it wiped off with the wiping cloth which loaded (125g / 3.9cm2). The sensory evaluation was performed on the glass plate after wiping by five monitors. The monitor evaluated the state when looking at the glass plate according to the following criteria, and those with 20 points or more were judged as ◯, and those with 20 points or less were judged as x.
5 points: The glass plate is not very dirty and very clean.
4 points: The glass plate is clean and not felt dirty.
3 points: The glass plate may be dirty, but it is clean.
2 points: Slightly dirty so that it is assumed that the glass plate would be dirty.
1 point: Dirty enough to be sure that the glass plate would have been dirty.
(5) Dust generation evaluation method The wiping cloth was similarly fixed to the weight used in the wiping performance evaluation method, and the glass plate on which no artificial qualities were adhered was wiped off with the wiping cloth. The sensory evaluation was performed on the glass plate after wiping by five monitors. The monitor evaluated the state when looking at the glass plate according to the following criteria. When there were 4 or more people as ◯, it was judged as ◯, and when it was 4 or less, it was judged as x.
○: Glass is not soiled with fibers and is good.
X: The glass is dirty with fibers and is defective.

[Example 1]
A two-layer structure yarn was prepared using the following yarns.
For the multifilament A ′, first, the sea component is modified polyethylene terephthalate copolymerized with 9 mol% of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4,000, and the island component is polyethylene terephthalate. Dissolution rate ratio; sea / island = 50, weight ratio; island: sea = 70: 30, multi-filament A ′ has 10 discharge holes with a diameter of 0.3 mm, where the number of islands per filament is 1,000. The melt was discharged by using a spinneret at a spinning temperature of 285 ° C., cooled and solidified by a spinning cooling device, applied with an oil agent, taken up at a speed of 1000 m / min on a preheating roller heated to 90 ° C., and heated to 140 ° C. Stretched 3.9 times between the heated set rollers and then scraped off with a scraper, 50 dtex, 10 filaments To obtain a multi-filament A 'of boiling water shrinkage percentage of 8%.

  Multifilament B is a polyethylene terephthalate with an intrinsic viscosity of 0.64 copolymerized with 10 mol% of isophthalic acid, discharged through a spinneret with a diameter of 0.3 mm and 12 holes, cooled and solidified by a spinning cooling device, After the application, 1000 m / min. An undrawn yarn wound at a speed was obtained. The obtained undrawn yarn was roller-drawn at a preheating temperature of 75 ° C. and a draw ratio of 3.3 times, and then heat-set at 95 ° C. and wound to obtain a multifilament B having 36 dtex, 12 filaments and a boiling water shrinkage of 25%. It was.

  Both yarns (multifilament A ′ yarn package 1 and multifilament B yarn package 2) are subjected to the manufacturing process shown in FIG. 1, and are first aligned by a cot roller 3, the cot roller 3 and the first take-up roller 5, Between the first take-up roller 5 and the second take-up roller 7 using a specific contact heater 6 and wound up on a take-up bobbin 8. A blended yarn was obtained.

  The resulting blended yarn was plain woven with a warp and weft of 87 wings x 3 pieces / K and 100 twists on the warp. The obtained woven fabric is immersed in an aqueous solution of sodium hydroxide having a concentration of 3.5% by weight and a bath temperature of 98 ° C. to remove sea components, dried and shrunk, and a multifilament B having a single yarn fineness of 3.0 dtex and a sheath at the core. A woven fabric made of ultra-fine polyester double-layered yarn made of multifilament A having a single yarn fineness of 0.004 dtex was obtained. The characteristics of this product are shown in Table 1 below.

[Example 2]
For the multifilament A ′, first, the sea component is nylon 6 and the island component is polyethylene terephthalate, and only nylon 6 is dissolved, and the island / sea (weight ratio) = 70: 30. 75, having a total of 6 discharge holes with a diameter of 0.3 mm with 500 islands, melted and discharged at a spinning temperature of 280 ° C. using a spinneret, cooled and solidified by a spinning cooling device, and then applied an oil agent. Taken up to a preheating roller heated to ℃ at a speed of 1000 m / min, stretched 3.9 times with a heat setting roller heated to 150 ℃, then scraped with a scissor, 30 dtex, 6 filament, boiling water shrinkage A multifilament A ′ having a rate of 10% was obtained.
For the multifilament B, a multifilament prepared by the same method as in Example 1 and made of polyethylene terephthalate, 20 dtex, 10 filaments and a boiling water shrinkage of 25% was used.

  Both yarns (multifilament A ′ yarn package 1 and multifilament B yarn package 2) are subjected to the manufacturing process shown in FIG. 1, and are first aligned by a cot roller 3, the cot roller 3 and the first take-up roller 5, Between the first take-up roller 5 and the second take-up roller 7 using a specific contact heater 6 and wound up on a take-up bobbin 8. A blended yarn was obtained.

  The obtained blended yarn was plain woven with a warp and weft of 87 wings x 3 pieces / K, with 100 warps twisted. The obtained woven fabric was immersed in formic acid to remove sea components and dried to obtain a mixed yarn woven fabric having a single yarn fineness of 0.007 dtex and 2.0 dtex. This woven fabric is immersed and contracted in boiling water to obtain a woven fabric made of ultra-thin polyester double-layered yarn consisting of multifilament B having a single yarn fineness of 2.0 dtex in the core and multifilament A having a single yarn fineness of 0.007 dtex in the sheath. It was. The characteristics of this product are shown in Table 1 below.

[Comparative Example 1]
In Example 1, as the multifilament A ′, sea terephthalate is a polyethylene terephthalate copolymerized with 9 mol% of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4,000. 50 dtex, 10 filaments, multifilaments having a boiling water shrinkage rate of 8% made of type composite fibers (24 islands, dissolution rate ratio; islands: sea = 1: 50, islands: sea (weight ratio) = 70: 30) The other fabrics were made under the same conditions. A woven fabric made of a two-layer structure yarn having a multifilament with a single yarn fineness of 3.0 dtex in the core and a single yarn fineness of 0.14 dtex in the sheath was obtained. When this fabric was used to wipe a platform with oil stains and water droplets, the fineness was outside the scope of the present invention, so a small amount of dirt and water droplets remained, and the wiping performance was poor. The characteristics of this product are shown in Table 1 below.

[Comparative Example 2]
In Example 2, 30 dtex, 24 filaments composed of a multi-filament A ′ sea-island composite fiber (300 islands, islands: sea (weight ratio) = 70: 30) where the sea component is nylon 6 and the island component is polyethylene terephthalate. A multifilament having a boiling water shrinkage of 18% was used, and a fabric was then produced under the same conditions. The surface layer portion of the obtained woven fabric has a mixture of single yarn fineness of 0.007 dtex and 3.0 dtex, and when this fabric is used to wipe oil stains and a table with water droplets, a small amount of dirt and water droplets remain, The wiping performance was poor. The characteristics of this product are shown in Table 1 below.

  The wiping cloth of the present invention has high wiping properties such as oil and water, high dust trapping power, and low dust generation, so it can be used for household cleaning cloths, glasses and lens wipes, and industrial applications. For example, it can be used in IC or semiconductor manufacturing factories or clean rooms.

Production process of the two-layer structured yarn of the present invention Example of spinneret for filament A '

Explanation of symbols

1: Multifilament A yarn package
2: Multifilament B yarn package
3: cot roller
4: Interlace nozzle
5: Heating roller
6: Specific contact heater
7: Take-off roller
8: Winding bobbin a: Spinneret b: Island component polymer reservoir c: Island component polymer introduction passage (hollow pin)
d: Sea component polymer introduction passage e: Pre-distribution sea component polymer reservoir f: Core-sheath type composite flow passage g: Merge passage h: Discharge hole

Claims (7)

A double-layer structure yarn in which a multifilament A having a single yarn fineness of 0.001 to 0.01 dtex and a multifilament B having a single yarn fineness of 0.1 to 10 dtex are mixed, The number of locations where the multifilament B appears on the fiber surface is 20 pieces / m or less, the multifilament A is mainly disposed in the sheath portion, and the multifilament B is mainly disposed in the core portion. Extra-fine two-layer yarn.
(1) Strength of multifilament A ≧ 3.0 cN / dtex
(2) 20 / m ≦ entangled number of double-layer structure yarn ≦ 100 / m   The ultra-thin bilayer structured yarn according to claim 1, wherein the weight ratio of the multifilament A and the multifilament B is 20:80 to 80:20.   Both the multifilament A and the multifilament B are polyester, The ultra fine two-layer structure yarn according to any one of claims 1 and 2. The multifilament A dissolves and removes the sea component of a sea-island type composite fiber multifilament (sometimes referred to as multifilament A ′) composed of an island component and a sea component whose dissolution rate ratio to the solvent satisfies the following formula: The ultrafine two-layer structure yarn according to any one of claims 1 to 3, wherein the yarn is obtained.
Dissolution rate ratio: 30 ≦ sea component dissolution rate / island component dissolution rate ≦ 5,000   The ultra-thin bilayer structured yarn according to claim 4, wherein the weight ratio of the sea component and the island component of the multifilament A 'is 40:60 to 5:95. Sea island type composite fiber multifilament A ′ having a boiling water shrinkage difference satisfying the following conditions and multifilament B having a single yarn fineness of 0.1 to 10 dtex are aligned and entangled, and then subjected to shrinkage treatment, and then the sea of multifilament A ′ The components were dissolved and removed, and the multifilament A having a single yarn fineness of 0.001 to 0.01 dtex was mainly arranged in the sheath portion, and the multifilament B having a single yarn fineness of 0.1 to 10 dtex was mainly arranged in the core portion. A method for producing an ultrafine two-layer structured yarn, characterized in that the yarn is a two-layer structured yarn.
10% ≦ Δ boiling water shrinkage ≦ 40%
[Δ Boiling Water Shrinkage: Boiling Water Shrinkage of Multifilament B−Boiling Water Shrinkage of Multifilament A ′] A multifilament A having a single yarn fineness of 0.001 to 0.01 dtex and a multifilament B having a single yarn fineness of 0.1 to 10 dtex are mixed, and the multifilament The number of locations where B appears on the fiber surface is 20 pieces / m or less, the multifilament A is mainly disposed in the sheath portion, and the multifilament B having a single yarn fineness of 0.1 to 10 dtex is mainly disposed in the core portion. A wiping cloth comprising an ultra-fine two-layer structure yarn that satisfies the following requirements.
(1) Strength of multifilament A ≧ 3.0 cN / dtex
(2) 20 / m ≦ entangled number of double-layer structure yarn ≦ 100 / m

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