Wiping cloth

Abstract

This product provides a wiping cloth suitable for media cleaning applications that suppresses the increase of particles due to friction during wiping, prevents contamination problems, offers high wiping performance, and leaves minimal residue. [Solution] A wiping cloth made of a fibrous structure using ultrafine polyamide fibers, wherein the single filament fineness of the ultrafine polyamide fibers is 0.7 dtex or less, the content of ultrafine polyamide fibers in the entire wiping cloth is 40% by mass or more, and the average number of airborne particles with a diameter of 0.1 μm or more is 10 particles / cm 2 The following is the wiping cloth.

Description

Technical Field

[0001] The present invention relates to a wiping cloth suitably used for cleaning media in magnetic recording media such as hard disks.

Background Art

[0002] Conventionally, for cleaning media in magnetic recording media such as hard disks, a fabric made of ultrafine fibers has been widely used as a wiping tape.

[0003] In most cases, for the weft yarns in the wiping direction (perpendicular to the traveling direction), split yarns obtained by chemically or physically treating mainly polyester single yarns or composite fibers composed of a polyester / polyamide composition are used.

[0004] Compared with polyamide, polyester has excellent morphological stability, less oligomer generation and dust absorption, and excellent processability in a dyeing kettle. Therefore, polyester fibers are preferably used for wiping tapes, and in many wiping tapes, polyester accounts for 60% by mass or more.

[0005] Although polyamide is inferior to polyester in these respects, it has high wear resistance, so less particles are generated due to friction during media wiping. The use of polyamide is also preferable in terms of less particle generation, but polyamide has a lot of contamination (hereinafter referred to as contamination) by oligomers and the like. Since a large amount of contamination damages the media during wiping, it was necessary to reduce the contamination.

[0006] As a means for reducing contamination, it has been proposed to use fibers not containing a matting agent such as titanium oxide as the weft or warp yarns to form a wiping tape (Patent Document 1).

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-147017 [Overview of the project] [Problems that the invention aims to solve]

[0008] Patent Document 1 states that long fibers or split fibers that have not undergone chemical splitting treatment are used as fibers that do not contain the matting agent, but the examples specifically mention long fibers, not split fibers, and the long fibers described in the examples have a thick single-fiber fineness and a round fiber cross-section, so their wiping performance is insufficient. Furthermore, as split fibers that have not undergone chemical splitting treatment, split fibers obtained by heat treatment, a physical splitting process after weaving, which separates the fibers due to differences in shrinkage rates, are mentioned. Split fibers obtained by physical splitting treatment generate a thin peeling film at the split portion, causing self-dusting and worsening the cleanliness.

[0009] The present invention has been made in view of the above-mentioned background art, and its purpose is to provide a wiping cloth suitable for media cleaning applications that suppresses the increase of particles due to friction during wiping, prevents contamination problems, has high wiping performance, and leaves few residues. [Means for solving the problem]

[0010] The object of the present invention is a wiping cloth made of a fibrous structure using ultrafine polyamide fibers, wherein the single filament fineness of the ultrafine polyamide fibers is 0.7 dtex or less, the content of ultrafine polyamide fibers in the entire wiping cloth is 40% by mass or more, and the average number of airborne particles with a diameter of 0.1 μm or more is 10 particles / cm². 2 This is achieved by the following wiping cloth.

[0011] Furthermore, it is preferable that the ultrafine polyamide fibers are polyamide fibers obtained by dissolving an alkali-soluble polyester resin of a segmented composite fiber consisting of a polyamide component and an alkali-soluble polyester component, which substantially does not contain a matting agent, and that the cross-sectional shape of the polyamide fibers is an irregular cross-sectional shape.

[0012] Furthermore, it is preferable that the fibrous structure is a woven fabric in which at least the ultrafine polyamide fibers are used as weft threads.

[0013] Furthermore, the object of the present invention is achieved by a method for manufacturing a wiping cloth, which comprises the steps of weaving a fabric using a split-type composite fiber consisting of a polyamide component and an alkali-soluble polyester component, which is substantially free of a matting agent, at least as the weft, and dissolving the alkali-soluble polyester resin by immersing the obtained fabric in an alkaline solution. [Effects of the Invention]

[0014] The wiping cloth of the present invention has an extremely low amount of ultrafine particles, thus preventing contamination. Furthermore, by containing a specific amount or more of polyamide fibers, it suppresses the increase of particles due to friction during wiping. In addition, by using ultrafine polyamide fibers with a single filament fineness of 0.7 dtex or less, it has high wiping performance and leaves little residue, making it a wiping cloth suitable for media cleaning applications. Furthermore, by weaving a fabric using a split-type composite fiber, which is substantially free of matting agents and consists of polyamide resin and alkali-soluble polyester resin, at least in the weft, and then dissolving the alkali-soluble polyester resin with an alkaline solution, oligomers and other substances contained in the polyamide and alkali-insoluble polyester are removed, thereby reducing the number of particles generated by self-dusting in the wiping cloth. [Brief explanation of the drawing]

[0015] [Figure 1] An explanatory diagram showing an example of the cross-sectional shape of an ultrafine fiber according to the present invention. [Figure 2] Explanatory drawing showing another example of the cross-sectional shape of the ultra-fine fiber according to the present invention. [Figure 3] Explanatory drawing showing another example of the cross-sectional shape of the ultra-fine fiber according to the present invention.

Mode for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail.

[0017] The wiping cloth of the present invention is a fiber structure using ultra-fine polyamide fibers.

[0018] The ultra-fine fibers constituting the wiping cloth need to be polyamide fibers having a single-filament fineness of 0.7 dtex or less. Further, the single-filament fineness is preferably 0.6 dtex or less. If the single-filament fineness is 0.7 dtex or less, the resulting wiping cloth is more excellent in flexibility and denseness and is suitable for polishing performance and cleaning performance.

[0019] The content of the ultra-fine polyamide fibers in the whole wiping cloth of the present invention needs to be 40% by mass or more. If the content is 40% or more, the generation of particles due to friction during media wiping is small.

[0020] The wiping cloth of the present invention preferably contains 30% or more of polyester. By using polyester fibers or composite fibers containing polyester in the warp, the form stability is improved, and it is easy to maintain the tape width when used as a wiping tape.

[0021] The average value of the number of airborne particles having a diameter of 0.1 μm or more in the wiping cloth of the present invention is 10 or less. 10 particles / cm 2 If it is 10 or less, it is difficult to damage the media.

[0022] The wiping cloth of the present invention has excellent wiping performance when used in the manufacturing process of hard disks and other precision equipment in cleanrooms. The wiping cloth can be used in the form of a string, tape, square, or any other shape cut to a predetermined size and shape.

[0023] In the present invention, the ultrafine polyamide fiber is preferably a fiber formed by splitting a split-type composite fiber, which consists of a polyamide component and an alkali-soluble polyester component, by alkali treatment.

[0024] Examples of the polyamide components mentioned above include aliphatic polyamides such as polyamide 6, polyamide 6,6, and polyamide 4,6.

[0025] Furthermore, a polyamide resin composition comprising an aromatic polyamide and an aliphatic polyamide may be used as the polyamide component. Examples of aromatic polyamides include polyamides having aliphatic dicarboxylic acids and aromatic diamines as the main structural units. The above polyamide resin composition exhibits high shrinkage performance, resulting in good splitting properties upon alkaline dissolution treatment or hot water treatment. The resulting fibrous structure is dense and bulky, providing wiping performance suitable for polishing and cleaning hard disks and other devices.

[0026] Specifically, examples include a resin obtained from metaxylylenediamine and adipic acid as the aromatic polyamide (polyamide MXD6), and a resin obtained from ε-caprolactam as the aliphatic polyamide (polyamide 6). The preferred mass mixing ratio of polyamide MXD6 and polyamide 6 is 35:65 to 70:30.

[0027] On the other hand, the above-mentioned alkali-soluble polyester components include polyalkylene glycols, isophthalic acid components containing metal sulfonate groups, and polyester components copolymerized with adipic acid.

[0028] In particular, it is preferable that the polyester has ethylene terephthalate as its main repeating unit, contains 2.0 to 3.0 mol% of a metal sulfonate group-containing isophthalic acid component in the acid component, and contains 9 to 13% by mass of polyalkylene glycol with an average molecular weight of 1000 to 10000 in the polymer. Furthermore, it is preferable that the polyester component has a mol% of DEG contained in it of 4.7 to 5.7 mol% in the glycol component, and the ratio of the maximum value [η]max to the minimum value [η]min of the intrinsic viscosity is 1.0 ≤ [η]max / [η]min ≤ 1.02.

[0029] The metal sulfonate group-containing isophthalic acid component used in the present invention is either dimethyl 5-metal sulfisoisophthalate (hereinafter referred to as SIPM) or a compound obtained by esterifying a methyl group with ethylene glycol (hereinafter referred to as SIPE). Since adding a large amount of SIPM to the slurry tank can worsen the properties of the slurry, SIPE is preferred. Sodium, potassium, lithium, etc., can be used as the metal in SIPM or SIPE, but sodium is the most preferred. The copolymerization ratio of SIPE is preferably 2.0 to 3.0 mol% of the acid component of the polymer. If the copolymerization ratio of SIPE is lower than this, it tends to be difficult to obtain sufficient alkaline solubility. On the other hand, if the copolymerization ratio is higher than this, thickening and gelation due to the charge of SIPE occur during the melt spinning process, which tends to significantly reduce operability.

[0030] Furthermore, polyalkylene glycols have the general formula HO(C n H 2n It is expressed as 0)mH (where n and m are positive integers), and polyethylene glycol (hereinafter referred to as PEG) with n=2 is the most general-purpose and preferred. The molecular weight of the polyalkylene glycol used in this invention is preferably 1,000 to 10,000. If the molecular weight is less than 1,000, hydrolysis of the modified polyester is likely to occur during melt spinning, resulting in insufficient heat resistance of the polyester and a tendency for fusion of polyester pellets and generation of white powder during the false twisting process. Furthermore, if the molecular weight exceeds 10,000, polymerization reactivity becomes poor, and polyalkylene glycol is less likely to copolymerize into the polyester molecular chain, resulting in a tendency for the polyester to have poor oxidation resistance.

[0031] The copolymerization amount of polyalkylene glycol should be 9 to 13% by mass relative to the polymer. If the copolymerization amount is less than 9% by mass, sufficient alkaline water solubility tends not to be obtained. On the other hand, if it exceeds 13% by mass, the heat resistance and oxidation resistance of the polymer deteriorate.

[0032] The intrinsic viscosity of the above polyester is such that the ratio of the maximum value [η]max to the minimum value [η]min is 1.0 ≤ [η]max / [η]min ≤ 1.02. If [η]max / [η]min falls outside this range, yarn breakage during melt spinning occurs frequently, spinneret life is shortened due to poor spinneret filtration, and other operational issues tend to occur.

[0033] Furthermore, the alkali-soluble polyester component used in the present invention preferably contains 4.7 to 5.7 mol% of diethylene glycol (DEG) in the glycol component. This DEG is produced by a side reaction during polymerization. If the DEG content is less than 4.7 mol%, the alkali water solubility is poor. If it exceeds 5.7 mol%, the heat resistance and oxidation resistance of the polymer are poor, and the operability during melt spinning becomes significantly worse.

[0034] Furthermore, it is preferable that the above-mentioned polyamide component and alkali-soluble polyester component do not contain a matting agent. A matting agent is an inorganic or organic particle such as titanium dioxide, silicon dioxide, and aluminum oxide that is usually added to suppress the gloss of the yarn or to improve spinning performance. In this context, "not containing a matting agent" means that matting agents such as titanium dioxide, which are usually added to suppress the gloss of the yarn or to improve spinning performance, are not actively added. This is because if a matting agent is included, it may come off due to the physical force during wiping, causing scratches on magnetic recording media, etc. In addition, trace amounts may be present due to contamination during the manufacturing and processing stages. Even in such cases, if the analytical value using a general ash content measurement method is less than 50 ppm in the polymer, it will not damage the surface during hard disk polishing or cleaning.

[0035] When the above-mentioned composite fibers are subjected to alkaline dissolution processing, the polyester component dissolves completely and the fibers are split. Furthermore, heating during this alkaline dissolution process, or through separate heat treatment, causes the polyamide component to shrink, resulting in a high-density, bulky wiping cloth.

[0036] The cross-sectional shape of the above-mentioned segmented composite fiber is preferably such that the polyamide component and the alkali-soluble polyester component are joined along the longitudinal direction of the single fiber in a shape where one component does not completely encompass the other component in the cross-section of the single fiber. Specifically, examples include radial segmented composite fibers joined in a radial and complementary radial shape as shown in Figures 1 and 2, and central circular segmented composite fibers as shown in Figure 3.

[0037] In the figure, 1 and 2 represent a polyamide component or an alkali-soluble polyester component, respectively. That is, if one is a polyamide component, the other is an alkali-soluble polyester component. In the present invention, using a split-type composite fiber in which 1 is an alkali-soluble polyester component and 2 is a polyamide component is preferable in that it allows the abrasion resistance of the polyamide to be more fully exhibited.

[0038] As described above, the ultrafine polyamide fibers in the present invention are preferable in terms of wiping performance during media cleaning if the fiber cross-sectional shape is an irregular cross-sectional shape.

[0039] The total fineness of the above-mentioned split composite fibers can be appropriately determined within the spinnable range. From the viewpoint of fiber shrinkage performance, which affects the wiping performance of the wiping cloth, a total fineness of 30 to 300 dtex is preferable. More preferably, it is 40 to 200 dtex, and particularly preferably 50 to 150 dtex.

[0040] Examples of fiber structures using the above-mentioned segmented composite fibers include yarns, woven fabrics, knitted fabrics, and nonwoven fabrics, with woven fabrics being preferred. When used as a wiping tape, woven fabrics are less prone to warp stretching. If the tape stretches warp during use, it cannot be wound up properly. In addition, narrowing the width can cause problems such as leaving unwiped areas on the wiping surface when it comes into contact with the wiping surface.

[0041] If the above fiber structure is a woven fabric, examples of weave structures include plain weave, satin weave, and twill weave. For wiping cloths, plain weave, satin weave, and twill weave are preferred, for example. Satin weave is preferred because it allows for a denser fabric.

[0042] Furthermore, if the fibrous structure is a woven fabric, the segmented composite fiber can be used in the weft, warp, or both.

[0043] In this case, it is preferable to use regular polyester fibers (polyethylene terephthalate fibers) or polyamide fibers for the warp threads.

[0044] In particular, when using the wiping cloth of the present invention in a tape-like shape, it is preferable that the weft yarn be made of ultrafine polyamide fibers. Using ultrafine polyamide fibers as the weft yarn in the wiping direction (perpendicular to the direction of travel) results in good wiping performance. Therefore, it is preferable to use the above-mentioned segmented composite fibers as the weft yarn during weaving.

[0045] In this case, it is preferable to use regular polyester fibers (polyethylene terephthalate fibers) for the warp threads.

[0046] When used in woven fabrics, the preferred finishing cover factor (K), calculated using the following formula, is preferably 1000 or more for warp and 800 or more for weft in the case of plain weave, and preferably 1200 or more for warp, more preferably 1500 or more for warp, more preferably 800 or more for weft, and more preferably 1000 or more for satin weave.

[0047]

number

[0048] When the fiber structure of the present invention is a knitted fabric, it may be warp knitted or weft knitted. Specifically, a weft knitted structure is preferred, and when used as a wiping cloth, for example, an interlock structure is preferred. When the fiber structure of the present invention, which is a knitted fabric, is used as a wiping cloth in a cleanroom, for example, it is preferable to have a wale count of 70 to 100 threads / inch and a course count of 70 to 100 threads / inch. In the case of tricot, it is preferable to use about 28G. Furthermore, even if the split-type fibers are used for all of the front yarn, back yarn, and middle yarn, or if only a part of them are split-type fibers, it is more preferable to use them for at least the front and back.

[0049] The wiping cloth of the present invention is preferably obtained by manufacturing a fibrous structure from the above-mentioned segmented composite fibers by a conventional method, then splitting the segmented composite fibers by alkaline dissolution treatment, and further performing heat treatment or the like as necessary.

[0050] Alkaline dissolution treatment removes oligomers and other substances contained in polyamides and polyesters using an alkaline aqueous solution, thereby reducing the number of self-generated particles in the wiping cloth.

[0051] The alkaline dissolution treatment is a method in which the split composite fibers of the present invention are immersed in a heated alkaline solution, dissolving the alkali-soluble polyester component and simultaneously shrinking the polyamide component to cause splitting. In this process, self-generated fine particles and low molecular weight substances mainly derived from oligomers contained in the alkali-soluble polyester component are dissolved and removed by the alkaline solution, thereby reducing the number of self-generated particles in the product.

[0052] The conditions for the alkaline dissolution treatment can be those generally used in the weight reduction processing of polyester fiber structures, for example, a method using a 0.5 to 5% by mass aqueous solution of sodium hydroxide can be used. More preferably, it is 1 to 3% by mass, and particularly preferably, 1 to 2% by mass. The treatment temperature is preferably 85 to 100°C, and more preferably 90 to 98°C.

[0053] Furthermore, it is preferable to heat-treat the fiber structure obtained by the above-mentioned alkaline dissolution treatment. Such heat treatment can shrink the fibers, increase the density of the fabric, increase the surface area of ​​the fabric, and improve its wiping properties. The heat treatment conditions can be, for example, 120-150°C for 0.5-1 hour under moist heat conditions, or 150-190°C for 30 seconds-1 minute under dry heat conditions. The above heat treatment may be performed simultaneously with the dyeing treatment. That is, the fibers may be shrunk by the heat treatment for dyeing.

[0054] In the method for manufacturing the wiping cloth of the present invention, it is preferable to obtain the final fiber structure by performing the above-described processes on the raw fabric obtained through processes such as weaving and knitting, thereby shrinking the woven fabric by 10-30% in the width direction and the knitted fabric by 40-60% in the width direction. Obtaining such a shrinkage rate is preferable in that it provides excellent wiping properties. The above shrinkage rate is determined by W0 being the width of the raw fabric and W being the width after shrinkage. 100 × {(W0 - W) / (W0)} (%) It can be calculated using the following formula.

[0055] Then, when used for polishing or cleaning precision electronic equipment such as hard disks in a cleanroom, the obtained fabric is washed with pure water in the cleanroom and dried, and cut to the desired size as needed. After that, if necessary, it is washed with pure water in the cleanroom and dried to obtain a wiping cloth. The obtained wiping cloth can be sealed in a resin film pack. When using this sealed pack in the manufacturing process of hard disks, etc., the pack can be opened and the wiping cloth can be used.

[0056] The wiping cloth of the present invention, obtained as described above, contains a large amount of ultrafine polyamide fibers, and has an average number of airborne particles with a diameter of 0.1 μm or more of 10 particles / cm². 2 As described below, it does not cause contamination and has excellent wiping properties. [Examples]

[0057] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below.

[0058] Furthermore, the evaluation methods are as follows:

[0059] <Intrinsic viscosity of polyester> The intrinsic viscosity [η] was measured by a conventional method using an automatic viscometer in a mixed solvent of phenol / tetrachloroethane = 6 / 4 (mass ratio) at 20°C.

[0060] <Relative viscosity of polyamide> The relative viscosity ηrel was measured using a conventional method with an Oswald viscometer at 20°C in a sulfuric acid solvent.

[0061] <Measurement of airborne particle count> A 1cm wide tape-like wiping cloth was cut to a length of 20cm and used as a sample. In a Class 100 cleanroom, the sample was placed on the measuring stage of a surface particle detector (Pentagon Technologies QIII Ultra®) with both ends fixed with a jig, and the total number of particles between 0.1μm and 5μm in diameter on the sample surface was measured. Three different locations on the same sample were measured, and the average value was taken as the number of airborne particles with a diameter of 0.1μm or larger. The unit of the total number of particles is particles / cm. 2 That is the case.

[0062] <Media wiping evaluation> A disc-shaped glass media is mounted on a device capable of rotating at 1000-3000 rpm, and each is coated with a wiping cloth at 150 g / cm². 2 The media was rotated for one minute while being pressed down with pressure at rotational speeds of 1000 rpm and 3000 rpm. The number of bright spots, believed to be dust, transferred onto the media was measured using a VisionScyTec Micro-MAX. All of these operations were performed in a Class 100 cleanroom.

[0063] (Example 1) As the polyamide component, we used polyamide 6 (manufactured by Ube Industries, Ltd.) with a relative viscosity of 2.7, which is substantially free of matting agents (titanium dioxide). On the other hand, as the alkali-soluble polyester component, we used copolymer polyethylene terephthalate (mainly composed of terephthalic acid and ethylene glycol, containing 2.3 mol% SIPE in the acid component, 10% by mass of polyethylene glycol with an average molecular weight of 8000, and 5.5 mol% DEG) with an intrinsic viscosity of 0.77, which is substantially free of matting agents. With a volume ratio of 3:7 between radially branching segment 1 and segment 2 that supplements the radial portion, melt-compound spinning was performed at a spinning temperature of 295°C and a spinning speed of 1050 m / min, so that the alkali-soluble polyester component constituted the radially branching segment 1 and the polyamide component constituted the segment 2 that supplements the radial portion, yielding an undrawn yarn with a fiber cross-sectional shape similar to that shown in Figure 2. The obtained undrawn yarn was then drawn using a roller heater at 85°C, a plate heater at 150°C, and a draw ratio of 3.0 to obtain a split-type composite fiber with 84 dtex / 25f. Then, using this drawn yarn as the weft and regular polyester fibers (intrinsic viscosity 0.61, 84 dtex / 36f) spun using polyethylene terephthalate without a matting agent as the warp, a back satin fabric was obtained. The obtained fabric was immersed in a 2 mass% sodium hydroxide aqueous solution (temperature 95°C) for 30 minutes to perform an alkaline dissolution treatment. After the alkaline dissolution treatment, the fabric was divided and shrunk by washing with pure water to obtain a wiping cloth. The polyamide fiber content in the weft of the obtained wiping cloth was 60 dtex / 200f, and the single yarn fineness was 0.29 dtex. In addition, the polyamide fiber content in the entire obtained wiping cloth was 40 mass%. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0064] (Example 2) A wiping cloth was obtained in the same manner as in Example 1, except that a split composite fiber (84 dtex / 28 f) with the same fiber cross-sectional shape as in Figure 1 was used as the weft, with a volume ratio of 3:7 between the radially branching segment 1 and segment 2 that supplements the radial portion, where the alkali-soluble polyester component constitutes the radially branching segment 1 and the polyamide component constitutes segment 2 that supplements the radial portion. The polyamide fiber content in the weft of the obtained wiping cloth was 60 dtex / 112 f, and the single filament fineness was 0.53 dtex. The polyamide fiber content in the entire obtained wiping cloth was 40% by mass. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0065] (Example 3) A wiping cloth was obtained in the same manner as in Example 1, except that a regular polyester fiber (intrinsic viscosity 0.61, 33 dtex / 12f) that was substantially free of a matting agent was used as the warp thread. The polyamide fiber content in the entire obtained wiping cloth was 45% by mass. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0066] (Example 4) A wiping cloth was obtained in the same manner as in Example 1, except that a core-sheath composite fiber (56dtex / 24f) was used as the warp thread, with the core being a regular polyester (intrinsic viscosity 0.61) that is substantially free of a matting agent and the sheath being polyamide 6 (manufactured by Ube Industries, Ltd.) with a relative viscosity of 2.7 that is substantially free of a matting agent. The polyamide content in the entire resulting wiping cloth was 50% by mass. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0067] (Comparative Example 1) A fabric was obtained in the same manner as in Example 1, except that a split composite fiber (56 dtex / 28 f) with the same fiber cross-sectional shape as in Figure 1 was used as the weft, with a volume ratio of 3:7 between the radially branching segment 1 and segment 2 that supplements the radial portion, and the radially branching segment 1 was composed of polyamide 6 (manufactured by Ube Industries, Ltd.) with a relative viscosity of 2.7 that is substantially free of a matting agent (titanium dioxide), and segment 2 that supplements the radial portion was composed of regular polyester with an intrinsic viscosity of 0.61 that is substantially free of a matting agent. The fabric was split by immersing the obtained fabric in a 2% by mass sodium hydroxide aqueous solution (temperature 95°C) for 20 minutes to perform a splitting treatment. After the splitting treatment, a shrinkage treatment was performed by washing with pure water to obtain a wiping cloth. The single filament fineness of the polyamide fibers in the weft of the obtained wiping cloth was 0.60 dtex. The polyamide fiber content in the entire obtained wiping cloth was 15% by mass. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0068] (Comparative Example 2) A fabric was obtained in the same manner as in Example 1, except that a split composite fiber (56 dtex / 28 f) with the same fiber cross-sectional shape as in Figure 1 was used as the weft, with a volume ratio of 3:7 between the radially branching segment 1 and segment 2 that supplements the radial portion, with regular polyester having an intrinsic viscosity of 0.61 and substantially no matting agent, constituting the radially branching segment 1, and polyamide 6 (manufactured by Ube Industries, Ltd.) having a relative viscosity of 2.7 and substantially no matting agent, constituting the segment that supplements the radial portion, and split composite fiber (56 dtex / 28 f) having the same fiber cross-sectional shape as in Figure 1 being used as the weft. The obtained fabric was subjected to a splitting treatment by immersing it in a 2 mass% sodium hydroxide aqueous solution (temperature 95°C) for 20 minutes. After the splitting treatment, it was subjected to a shrinkage treatment by washing with pure water to obtain a wiping cloth. The single filament fineness of the polyamide fiber in the weft of the obtained wiping cloth was 0.35 dtex. The polyamide fiber content in the entire obtained wiping cloth was 35 mass%. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0069] (Comparative Example 3) A fabric was obtained in the same manner as in Example 1, except that a split composite fiber (56dtex / 28f) with the same fiber cross-sectional shape as in Figure 1 was used as the weft, with a volume ratio of 3:7 between the radially branching segment 1 and the segment 2 that supplements the radial portion, and the radially branching segment 1 was composed of polyamide 6 (manufactured by Ube Industries, Ltd.) with a relative viscosity of 2.7 that is substantially free of a matting agent, and the segment 2 that supplements the radial portion was composed of regular polyester with an intrinsic viscosity of 0.61 that contains 0.3 mass% of a matting agent. The obtained fabric was subjected to a splitting treatment by immersion in a 2 mass% sodium hydroxide aqueous solution (temperature 95°C) for 20 minutes. After the splitting treatment, a shrinkage treatment was performed by washing with pure water to obtain a wiping cloth. The single filament fineness of the polyamide fibers in the weft of the obtained wiping cloth was 0.60dtex. The polyamide fiber content in the entire obtained wiping cloth was 15 mass%. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0070] (Comparative Example 4) A fabric was obtained in the same manner as in Example 1, except that a split composite fiber (56dtex / 25f) with the same fiber cross-sectional shape as in Figure 2 was used as the weft, and a core-sheath composite fiber (56dtex / 24f) was used as the warp, with the core being a regular polyester component (intrinsic viscosity 0.61) that is substantially free of a matting agent and the sheath being a polyamide 6 (manufactured by Ube Industries, Ltd.) that is substantially free of a matting agent and has a relative viscosity of 2.7. The obtained fabric was divided into a 2% by mass aqueous sodium hydroxide solution (temperature 95°C) for 20 minutes to perform a splitting treatment. After the splitting treatment, a shrinkage treatment was performed by washing with pure water to obtain a wiping cloth. The single filament fineness of the polyamide fibers in the weft of the obtained wiping cloth was 0.67 dtex. The total polyamide fiber content in the obtained wiping cloth was 15% by mass. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated. The results are shown in Table 1.

[0071] (Comparative Example 5) A back satin fabric was obtained using regular polyester fibers (33 dtex / 12 f) with an intrinsic viscosity of 0.61, which were substantially free of matting agents, as the warp threads, and polyamide 6 (manufactured by Ube Industries, Ltd.) single yarn (44 dtex / 36 f) with a relative viscosity of 2.7, which were substantially free of matting agents, as the weft threads. The fabric was subjected to a shrinkage treatment by washing it with pure water to obtain a wiping cloth. The single yarn fineness of the polyamide fibers in the weft threads of the obtained wiping cloth was 1.22 dtex. The polyamide fiber content in the entire obtained wiping cloth was 40% by mass. The obtained wiping cloth was heat-cut so that the weft direction became the width direction to create 1 cm wide tape-shaped wiping cloth, which was then evaluated.

[0072] [Table 1]

[0073] The wiping cloths of Examples 1-4 had few airborne particles with a diameter of 0.1 μm or larger, and also produced few remaining particles after wiping, thus suppressing the increase in contamination during wiping. On the other hand, the wiping cloths of Comparative Examples 1-4 were polyester-based wiping tapes, and as the rotation speed of the media increased, the number of particles increased, resulting in insufficient wiping. [Explanation of Symbols]

[0074] 1. Radially branching segments 2. Segments that supplement the radial portion

Claims

1. A wiping cloth made of a fibrous structure using ultrafine polyamide fibers, wherein the single filament fineness of the ultrafine polyamide fibers is 0.7 dtex or less, the content of ultrafine polyamide fibers in the entire wiping cloth is 40% by mass or more, and the average number of airborne particles with a diameter of 0.1 μm or more is 10 particles / cm². ２ The following is a wiping cloth.

2. The wiping cloth according to claim 1, wherein the ultrafine polyamide fibers are polyamide fibers obtained by dissolving the alkali-soluble polyester component of a split-type composite fiber that is substantially free of a matting agent and consists of a polyamide component and an alkali-soluble polyester component, and the cross-sectional shape of the fibers is an irregular cross-sectional shape.

3. The wiping cloth according to claim 2, wherein the fiber structure is a woven fabric in which at least the ultrafine polyamide fibers are used as weft threads.

4. A method for producing a wiping cloth according to claim 1, 2, or 3, comprising the steps of: weaving a fabric using a split composite fiber consisting of a polyamide component and an alkali-soluble polyester component, which is substantially free of a matting agent, as at least the weft; and dissolving the alkali-soluble polyester component by immersing the obtained fabric in an alkaline solution.

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