JP6163878B2 - Non-woven fabric and leather-like sheet using the same - Google Patents

Description

  The present invention relates to a nonwoven fabric composed of ultrafine fibers and suitably used for artificial leather, high-performance abrasive cloth, cleaning cloth, wiping cloth, etc., and more specifically, it can be achieved with conventional ultrafine fibers. The present invention relates to a non-woven fabric and a leather-like sheet-like material using the non-woven fabric, which can efficiently remove foreign matters widely distributed from a micronized to a few μm order.

  In recent years, as a hard disk polishing / cleaning application, a sheet-like material in which a polymer elastic body is applied as a cushion to a nonwoven fabric is suitably used. As the capacity of hard disks increases, the recording density of magnetic recording media is accelerating, and the flying height of the read / write head is significantly reduced. Along with this, fine foreign matter of the order of several tens of nm, which has not been regarded as a problem, affects the flying height of the head and causes an error in reading and writing. For this reason, mirror processing of the substrate surface and subsequent cleaning processing are regarded as important.

  As a substrate for a magnetic recording medium, an aluminum substrate or a glass substrate subjected to a nonmagnetic plating process such as Ni-P plating is used. Each substrate is subjected to mirror polishing using a polishing cloth for the purpose of imparting smoothness of 1-2 angstrom level to the substrate after performing primary polishing and secondary polishing by pad polishing or the like. ing. After that, a cleaning process using a cleaning cloth is performed in order to remove organic matter and minute dust adhering to the substrate surface and processing residues such as diamond abrasive grains and polishing scraps remaining on the substrate surface. After being dried, it is subjected to a film forming process of an underlayer, a magnetic layer, and a protective layer. At this time, if the magnetic recording medium is finished without completely removing the processing residue, problems such as a magnetic defect and an error defect due to the residue occur.

  From such a background, in order to clean the surface of the magnetic recording medium substrate, at least one surface of the nonwoven fabric has ultrafine fibers with an average single fiber diameter of 5 μm or less, and an elastic polymer is contained inside the nonwoven fabric. A cloth has been proposed (see, for example, Patent Document 1). According to this proposal, the scraping effect of ultrafine fibers is greatly improved, and magnetic defects and error defects can be satisfactorily suppressed. However, as the precision of the smoothness of the substrate surface has been further improved due to the remarkable increase in density in recent years, the minimization of foreign matters to be removed has further progressed, and the average single fiber diameter described in the literature is about 1.4 μm. In the fiber, the effect of removing foreign matters was not sufficient.

  In view of the above background, a cleaning cloth using ultrafine fibers having an average single fiber diameter of 1 to 400 nm has been proposed (see, for example, Patent Document 2). According to this proposal, the wiping performance of foreign substances is improved by nano-order ultra-fine fibers, but the ultra-fine fibers tend to aggregate due to a significant increase in specific surface area, and the characteristics as nano-order ultra-fine fibers are not fully utilized. It was.

  On the other hand, according to the known sea-island type composite spinning method as described in Patent Document 1, the diameter of the average single fiber is set to 1 μm or less, for example, about 0.8 μm, as shown in FIG. It is also possible to do. However, although the effect of scraping out fine foreign matter is improved by reducing the diameter of the single fiber, large foreign matters such as the order of several μm are likely to fall from these fibers, and it is easy to sufficiently remove these foreign matters. Not.

  Also, as shown in FIG. 3, for example, by using a known mixed spinning method, a non-woven fabric having a fiber diameter distribution of ultrafine fibers set to a wide range, for example, 0.5 to 1 μm or more, is used, and a fine nonwoven fabric is used. It is also conceivable to remove foreign matter to large foreign matter. However, when the fiber diameter distribution is set wide, the number of thin fibers and thick fibers occupying the entire ultrafine fiber is relatively small, for example, about 5% or less, respectively. There is a problem that it becomes difficult to remove.

  For this reason, in recent years, with the miniaturization of foreign matter to be removed, there is a need for a cleaning cloth that can efficiently remove residues and the like whose foreign matter size has become widely distributed on the order of several tens of nm to several μm. It was done.

Japanese Patent No. 4457758 JP 2008-55411 A

  Accordingly, an object of the present invention is to provide a wide range of foreign substances such as small pieces of polishing abrasive grains remaining on the surface of a magnetic recording medium substrate, processing residues such as polishing debris and slurry liquid, and the like, which are widely distributed from a finer one to several μm order. An object of the present invention is to provide a non-woven fabric and a leather-like sheet material using the non-woven fabric that can efficiently remove the substrate from the surface of the substrate.

  That is, the present invention is to solve the above-mentioned problems, and the present invention 1 relates to a nonwoven fabric, which is a sheet-like material composed of ultrafine fibers having a fiber diameter of 0.05 to 5.0 μm, and the ultrafine fibers The center value of a peak located on the larger diameter side is 1.3 of the center value of the peak adjacent to the smaller diameter side. It is characterized in that the total number of fibers larger than twice and within the range of the center value ± 30% of each peak occupies 90% or more of the total number of fibers.

  The present invention 2 relates to a leather-like sheet material, characterized by having the nonwoven fabric of the present invention 1 and containing an elastic polymer inside the nonwoven fabric.

  Here, the above-mentioned “fiber diameter” refers to the diameter when the ultrafine fiber has a circular cross section, and refers to the circular diameter having the same cross-sectional area when the ultrafine fiber has a cross section. In addition, the above “peak” means a point that is convex upward when a frequency distribution is created in increments of 0.1 μm with respect to the single fiber diameter, and the frequency distribution is graphed by a straight line or a curve. The value of the fiber diameter at is called the peak center value. However, when other peaks exist within the range of 1.3 times the center value of a certain peak, they are treated as one peak including them. The peak center value in this case refers to the center value of the peak with the highest frequency when the frequencies of the individual peaks are different, and refers to the average value of the peak center values when the frequencies of the individual peaks are equal.

  The non-woven fabric has two or more peaks in which the distribution of the ultrafine fiber diameters is different from each other, and the total number of fibers existing within the range of the center value ± 30% of each peak is 90% of the total number of fibers. In view of the above, each has a large number of finer fibers having a smaller diameter and a thicker fiber having a larger diameter. For this reason, fine foreign matters, for example, of the order of several tens of nm are favorably scraped with ultrafine fibers having a smaller diameter, and large foreign matters, for example, of the order of several μm, are favorably scraped with ultrafine fibers having a larger diameter. After that, the squeezed out foreign matter is firmly held by ultrafine fibers having a larger diameter.

  The diameter distribution of the ultrafine fibers preferably has at least one peak center value in the range of 0.05 to 1.0 μm and at least one peak center value in the range of 1.0 to 5.0 μm. In addition, it is more preferable because foreign substances distributed widely in the order of several tens of nm to several μm can be more effectively removed.

  When the ultrafine fiber is derived from a sea-island type composite fiber that generates ultrafine fibers having different thicknesses from one composite fiber, the ultrafine fiber constituting the nonwoven fabric is a fiber bundle derived from the sea-island type composite fiber. Thus, ultrafine fibers having different thicknesses are included. As a result, the above-mentioned nonwoven fabric is in a state in which thicker and finer fine fibers are uniformly dispersed at a predetermined ratio, so that foreign substances can be removed from the substrate surface and the like more uniformly, which is more preferable. .

  Since the nonwoven fabric of the present invention includes a large number of fine fibers having a smaller diameter and a fine fiber having a larger diameter, when the nonwoven fabric is used for a cleaning processed cloth, for example, a fine number such as an order of several tens of nm is used. Foreign matters can be scraped out with fine fibers having a smaller diameter, and larger foreign matters, for example, of the order of several μm can be securely grasped with ultra fine fibers having a larger diameter. That is, by using the nonwoven fabric of the present invention, fine foreign matter remaining on the surface of the magnetic recording medium substrate, small abrasive particles, processing residues such as polishing scraps and slurry liquid, etc. A cleaning cloth can be obtained that can efficiently remove foreign matters widely distributed in the order of several μm.

  In addition, when the leather-like sheet-like material of the present invention is a cleaning cloth, it has excellent wiping and gripping properties against foreign matters such as residues widely distributed on the order of several tens of nm to several μm. The removal efficiency of the foreign matter from the substrate surface and the like is extremely high, and cleaning using this can satisfactorily suppress the defect rate of the magnetic recording medium substrate.

It is a typical fiber diameter distribution figure of the ultrafine fiber which comprises this of the nonwoven fabric of this invention. It is a typical fiber diameter distribution figure of the ultrafine fiber which comprises the nonwoven fabric produced by the well-known sea-island type composite spinning method. It is a typical fiber diameter distribution figure of the ultrafine fiber which comprises the nonwoven fabric produced by the well-known mixed spinning method.

  The nonwoven fabric of the present invention is a sheet-like material composed of ultrafine fibers having a fiber diameter of 0.05 to 5.0 μm. For example, as shown in FIG. The center value of the peak located on the larger diameter side has two or more peaks whose distributions are different from each other, and is greater than 1.3 times the center value of the peak adjacent to the smaller diameter side, and each peak The total number of fibers existing within the range of the center value of ± 30% occupies 90% or more of the total number of fibers.

  In the present invention, the plurality of peak center values are not limited to specific values, but for example, by using ultrafine fibers in the range of 0.05 to 1.0 μm, fineness on the order of several tens to several hundreds of nanometers. In addition to improving the removal performance of residual residues, the removal performance of relatively large residues on the order of several hundreds of nanometers to several micrometers is also maintained by simultaneously adopting ultrafine fibers in the range of 1.0 to 5.0 μm. be able to. Therefore, by using ultrafine fibers with a fiber diameter distribution having two or more different peaks, the wiping and gripping effect is improved against residues and other foreign matters having a wide size distribution such as several tens of nm to several μm. To do.

  The peak of the distribution of the diameter of the ultrafine fiber referred to in the present invention means that when the frequency distribution (histogram) in increments of 0.1 μm is graphed by a straight line or a curve with respect to the diameter of the ultrafine fiber constituting the nonwoven fabric, as shown in FIG. The point which becomes convex upwards.

Examples of the polymer forming the ultrafine fiber used in the present invention include polyester, polyamide, polyolefin, polyphenylene sulfide (PPS), and the like. Many polycondensation polymers represented by polyester and polyamide have a high melting point and are excellent in heat resistance against heat generated during washing processing, and are preferably used in the present invention. Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate. Specific examples of the polyamide include nylon 6, nylon 66, nylon 12, and the like.
In addition, the polymer constituting the ultrafine fiber used in the present invention may be copolymerized with other components, and may contain additives such as particles, flame retardants and antistatic agents.

  It is important that the diameter of the ultrafine fiber used in the present invention is 0.05 to 5.0 μm. By setting the fiber diameter to 5.0 μm or less, preferably 4.0 μm or less, it is possible to ensure removal performance for large-size residues and other foreign matters without damaging the object to be wiped. On the other hand, by making the fiber diameter 0.05 μm or more, preferably 0.1 μm or more, it is possible to ensure the removal performance with respect to extremely small-sized residues and other foreign matters, and to maintain the fiber strength and rigidity. Therefore, the cleaning process can be performed efficiently.

  The nonwoven fabric of the present invention is obtained from a short fiber nonwoven fabric obtained by forming a laminated fiber web using a card and a cross wrapper and then needle punching or water jet punching, a spunbond method or a melt blow method. It is possible to appropriately employ a long-fiber nonwoven fabric obtained or a nonwoven fabric obtained by a papermaking method. Among them, a short fiber nonwoven fabric obtained by entanglement of fibers by applying a needle punch or a water jet punch is preferably used in the present invention because the aspect of the ultrafine fiber bundle can be controlled by the needle punch process. It is done.

  Although the leather-like sheet-like material of the present invention having the above-mentioned nonwoven fabric is preferably used for a washed cloth, the nonwoven fabric contains an elastic polymer. By containing the elastic polymer in the nonwoven fabric, it is possible to prevent the ultrafine fibers from falling out of the nonwoven fabric due to the binder effect of the elastic polymer, and to form uniform napping at the time of raising. Moreover, by containing an elastic polymer, cushioning properties can be imparted to the leather-like sheet material, and the occurrence of scratch defects and the like can be suppressed when used as a washed cloth.

  Examples of the elastic polymer used in the present invention include polyurethane, polyurea, polyurethane / polyurea elastomer, polyacrylic acid, acrylonitrile / butadiene elastomer, and styrene / butadiene elastomer. Among these, polyurethane elastomers such as polyurethane and polyurethane / polyurea elastomer are preferably used.

  As the polyol component of the polyurethane-based elastomer, a polyester-based, polyether-based or polycarbonate-based diol, or a copolymer thereof can be used. Moreover, as a diisocyanate component, aromatic diisocyanate, alicyclic isocyanate, aliphatic isocyanate, etc. can be used.

  The weight average molecular weight of the polyurethane elastomer is preferably 50,000 to 300,000. By setting the weight average molecular weight to 50,000 or more, more preferably 100,000 or more, and further preferably 150,000 or more, the strength of the nonwoven fabric can be maintained, and dropping of the ultrafine fibers can be prevented. Further, by setting the weight average molecular weight to 300,000 or less, more preferably 250,000 or less, it is possible to suppress the increase in the viscosity of the polyurethane solution and facilitate the impregnation of the ultrafine fiber layer.

The elastic polymer may contain other resins such as polyester resins, polyamide resins or polyolefin elastomer resins, acrylic resins or ethylene-vinyl acetate resins. Moreover, it is preferable to contain in the range which does not impair the characteristic of a polyurethane, as a content rate of these other resin, the range of 0-30 mass% is preferable, More preferably, it is 0-20 mass%. It is a range.
In addition, additives such as colorants, antioxidants, antistatic agents, dispersants, softeners, coagulation modifiers, flame retardants, antibacterial agents, and deodorants are blended in the elastic polymer as necessary. Also good.

  The content of the elastic polymer is preferably 5 to 200% by mass with respect to the nonwoven fabric (mass). Depending on the content of the elastic polymer, the surface state, cushioning properties, hardness, strength, etc. of the leather-like sheet can be adjusted. By setting the content of the elastic polymer to 5% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more, dropping of ultrafine fibers can be reduced. On the other hand, when the content of the elastic polymer is 200% by mass or less, more preferably 100% by mass or less, and further preferably 80% by mass or less, processability and productivity are improved, and ultrafine fibers are formed on the surface. A uniformly dispersed state can be obtained.

The basis weight of the leather-like sheet having the nonwoven fabric of the present invention is preferably 100 to 600 g / m ² . By making the basis weight 100 g / m ² or more, more preferably 150 g / m ² or more, it is excellent in form stability and dimensional stability when used as a cleaning cloth, and processing unevenness due to elongation of the nonwoven fabric during the cleaning process, Occurrence of scratch defects can be suppressed. On the other hand, by making the basis weight 600 g / m ² or less, more preferably 300 g / m ² or less, the handleability of the leather-like sheet is facilitated, and the cushioning property of the leather-like sheet is moderately suppressed, At the time of the cleaning process, the pressing pressure by the rubber roller from the non-polished surface can be appropriately propagated to the surface of the cleaning process, and an efficient cleaning process can be performed.

  The leather-like sheet-like material comprising the nonwoven fabric of the present invention is preferably a surface having a raised surface on the surface on the side subjected to the cleaning process and having raised hairs. By forming napping on the surface of the leather-like sheet material, it is possible to obtain a dispersion of ultrafine fibers having an irregular cross section, and furthermore, an appropriate cushioning property can be obtained for the surface fibers, so that residues such as residues are formed in the gaps between the fibers. A foreign object can be gripped, and the foreign object retention characteristics are improved.

  In the leather-like sheet-like material having the nonwoven fabric of the present invention and the cleaning cloth using the same, as the form of the structure of the surface fiber raised portion constituting the surface ultrafine fiber bundle, the ultrafine fibers may be evenly arranged. Further, the ultrafine fibers may be somewhat separated from each other, may be partially bonded, or may be aggregated. Here, the bond refers to a chemical reaction or physical fusion, and the aggregation refers to a molecular force such as a hydrogen bond.

Next, a method for producing the nonwoven fabric of the present invention will be described.
As a means for obtaining a nonwoven fabric such as a fiber entangled body in which ultrafine fiber bundles are entangled, it is preferable to use ultrafine fiber generating fibers. Although it is difficult to produce a nonwoven fabric such as a fiber entanglement directly from an ultrafine fiber, by producing a fiber entanglement from an ultrafine fiber generating fiber and generating an ultrafine fiber from a sea-island composite fiber in this fiber entanglement A nonwoven fabric formed by entanglement of ultrafine fiber bundles can be obtained.

  As the ultrafine fiber generation type fiber, one of two thermoplastic resins having different solvent solubility is used as a sea component, the other as an island component, and the sea component is dissolved and removed using a solvent or the like, thereby converting the island component into an ultrafine fiber. The sea-island-type fibers, or the two-component thermoplastic resin arranged alternately in a radial or multi-layer fashion on the fiber cross-section, and the release-type composite fiber that splits the components into ultra-fine fibers by splitting and separating each component. it can.

  For sea-island type fibers, sea-island type composite fibers that use a sea-island type composite base to spun two components of the sea component and the island component, and mixed spinning that mixes and spins the two components of the sea component and the island component are spun. There are fibers. However, from the point that ultrafine fibers controlled with high accuracy can be obtained, and a sufficiently long ultrafine fiber can be obtained, which contributes to the strength of the nonwoven fabric and the leather-like sheet-like material comprising the nonwoven fabric. A type composite fiber is preferably used.

  In the nonwoven fabric of the present invention, it is important that the distribution of the diameters of the ultrafine fibers constituting it has two or more peaks. By setting the number of peaks to 2 or more, the removal / gripping performance with respect to foreign matters such as residues having a size distribution of several nm to several μm is excellent. The number of peaks can be set as appropriate depending on the size and number distribution of foreign matters to be wiped off. The upper limit of the number of peaks is not particularly limited, but should be set to 10 or less from the viewpoint of the productivity of the distribution plate described later, the uniformity of the ultrafine fibers in each peak, the number of fibers contained in each peak, and the like. Is desirable.

  The ultrafine fibers constituting the nonwoven fabric of the present invention need only have a plurality of peaks in the distribution of diameters, and the plurality of peaks are formed by blending several types of sea-island composite fibers having different thicknesses, for example. It is also possible to do. However, when the above-mentioned peak is formed by using sea-island type composite fibers that generate ultrafine fibers having different thicknesses from one composite fiber, the ultrafine fibers having different thicknesses are uniform in the nonwoven fabric. Therefore, it is possible to contribute to the uniformity of the nonwoven fabric and to obtain a nonwoven fabric having a uniform surface, cross-sectional structure and mechanical properties, which is preferable.

  The sea-island type composite fiber that generates the above-mentioned ultrafine fiber, which is preferably used for the nonwoven fabric of the present invention, is prepared by using, for example, a composite base for discharging a polymer stream described in JP2011-174215A can do. This composite base is a combination of a measuring plate having a plurality of measuring holes for measuring the polymer flow of the sea-island component, and a distribution plate having a plurality of distributing holes in a merging groove for joining the discharged polymer flow from the plurality of measuring holes. In addition, from the obtained sea-island type composite fiber, it is possible to generate ultrafine fibers having a desired diameter or a vicinity thereof.

  At this time, the sea-island type composite fibers can be combined with each other from one composite fiber by combining a merge plate that recombines a part of the polymer uniformly distributed by the distribution plate. A sea-island type composite fiber that generates ultrafine fibers having different thicknesses can be obtained. By using this sea-island type composite fiber, two or more different peaks can be formed in the diameter distribution of the ultrafine fiber.

  As for the ratio of the sea component to the island component, the mass ratio of the island fiber to the sea-island type composite fiber is preferably 0.2 to 0.8, and more preferably 0.3 to 0.7. By setting the mass ratio to 0.2 or more, the removal rate of sea components is reduced and productivity is improved. Further, by setting the mass ratio to 0.8 or less, it is possible to improve the spreadability of the island fibers and prevent the island components from joining.

  As the sea component of the sea-island fiber, polyethylene, polypropylene, polystyrene, copolymer polyester obtained by copolymerizing sodium sulfoisophthalic acid, polyethylene glycol, or the like, or polylactic acid can be used.

  As a method for obtaining the above nonwoven fabric, as described above, a method of entanglement of a fiber web with a needle punch or a water jet punch, a spun bond method, a melt blow method, or a paper making method can be employed. In particular, in order to obtain the above-described form of the ultrafine fiber bundle, a method that undergoes processing such as needle punching or water jet punching is preferably used.

  In the needle used for the needle punching process, the number of needle barbs is preferably 1-9. By using one or more needle barbs, efficient fiber entanglement becomes possible. On the other hand, when the number of needle barbs is 9 or less, fiber damage can be suppressed.

The number of punching is preferably 1000 to 7000 / cm ² . By setting the number of punching to 1000 pieces / cm ² or more, denseness can be obtained and a highly accurate finish can be obtained. On the other hand, by setting the number of punching to 7000 / cm ² or less, deterioration of workability, fiber damage, and strength reduction can be prevented.

  Moreover, when performing a water jet punch process, it is preferable to perform water in the state of a columnar flow. Specifically, water may be ejected from a nozzle having a diameter of 0.05 to 1.0 mm at a pressure of 2 to 60 MPa.

It is preferable that the apparent density of the nonwoven fabric composed of ultrafine fiber-generating fibers after the needle punching process or the water jet punching process is 0.15 to 0.45 g / cm ³ . By setting the apparent density to 0.15 g / cm ³ or more, it can be made into a nonwoven fabric with excellent shape stability and dimensional stability, and suppress processing unevenness due to elongation of the cleaning processed cloth during the cleaning processing, and generation of scratch defects. Can do. On the other hand, when the apparent density is 0.45 g / cm ³ or less, a sufficient space for applying the elastic polymer can be maintained between the fibers.

  From the viewpoint of densification, the nonwoven fabric composed of the ultrafine fiber-generating fibers thus obtained is preferably shrunk by dry heat or wet heat, or both, and further densified. Moreover, you may compress in the thickness direction by a calendar process etc.

The ultrafine fiber generation processing for dissolving and removing the easily soluble polymer from the ultrafine fiber generation type fiber, such as dissolving sea components from the sea-island type composite fiber, is performed before or after applying the elastic polymer to the nonwoven fabric, or raising (Napping) may be performed at any timing before and after the treatment.
As the solvent for dissolving the above-mentioned easily soluble polymer (sea component), an organic solvent such as toluene or trichloroethylene is used if the sea component is polyolefin such as polyethylene or polystyrene, and the sea component is polylactic acid or copolymer polyester. If so, an alkaline aqueous solution such as sodium hydroxide can be used. The ultrafine fiber generation processing (sea removal treatment) can be performed by immersing a nonwoven fabric made of ultrafine fiber generation type fibers in a solvent and squeezing it.
For the ultrafine fiber generation processing, a known apparatus such as a continuous dyeing machine, a vibro-washer type seawater removing machine, a liquid dyeing machine, a Wins dyeing machine or a jigger dyeing machine can be used.

  The nonwoven fabric of the present invention is impregnated with an elastic polymer such as polyurethane as a main component to form a leather-like sheet. At this time, in order to obtain denseness and uniformity of the fiber distribution on the surface of the nonwoven fabric, the elastic polymer is not substantially present in the fiber bundle of the ultrafine fibers in the nonwoven fabric composed of the ultrafine fibers. It is preferable. When the elastic polymer is present even inside the fiber bundle, the elastic polymer is present by adhering to each ultrafine fiber, so that the surface fibers are easily torn during the buffing process and it is difficult to form napped hairs.

As a method of obtaining a form in which the elastic polymer does not substantially exist inside the fiber bundle of ultrafine fibers, for example, the elastic polymer is made into a solution with a solvent such as dimethylformamide,
(1) A nonwoven fabric composed of ultra-fine fiber-generating sea-island composite fibers is impregnated with the elastic polymer solution and coagulated in water or an organic solvent aqueous solution. A method of dissolving and removing the polymer with a solvent that does not dissolve,
(2) Polyvinyl alcohol having a saponification degree of preferably 80% or more is applied to the nonwoven fabric composed of the ultra-fine fiber-generating sea-island composite fiber, and after protecting most of the periphery of the fiber, the sea-island composite fiber A method of removing the polyvinyl alcohol after dissolving the sea component with a solvent that does not dissolve the polyvinyl alcohol, then impregnating the elastic polymer solution and coagulating it in water or an organic solvent aqueous solution.
Etc. can be preferably used.

  Examples of the solvent preferably used when the elastic polymer is applied to the nonwoven fabric include N, N'-dimethylformamide and dimethyl sulfoxide. In the case of polyurethane, a water-based polyurethane dispersed as an emulsion in water may be used.

  The elastic polymer is applied by, for example, immersing the nonwoven fabric in an elastic polymer solution dissolved in a solvent, and then dried to substantially solidify and solidify the elastic polymer. In drying, you may heat at the temperature which does not impair the performance of a nonwoven fabric and an elastic polymer.

  The raising | fluff process of the leather-like sheet-like thing which has the nonwoven fabric of this invention can be performed using sandpaper, a roll sander, etc. In particular, by using sandpaper, uniform and dense napping can be formed. Furthermore, in order to form the above-mentioned uniform ultrafine fiber napping on the surface of the sheet-like material obtained by applying an elastic polymer to the nonwoven fabric, the diameter of the ultrafine fiber and the abrasive grain size of the sandpaper used are It is preferable to control the ratio, the speed ratio between the sandpaper and the leather-like sheet, the grinding amount, the grinding load, and the like within an appropriate range. In order to reduce the grinding load, multi-stage buffing with 3 or more buff stages is used, with 70 to 90% of the total grinding amount in the first and second stages or more and 30 to 10% in the final stage. It is preferable to carry out and prepare the surface.

  By buffing the sheet-like material under the above conditions, the ultrafine fibers combined with an elastic polymer such as polyurethane are efficiently dug up, and the dispersibility of the surface fibers is ensured. By buffing grinding, it becomes possible to form a surface state in which the above-mentioned nappings composed of the ultrafine fiber bundles are densely arranged on the surface.

The cleaning cloth produced from the leather-like sheet-like material having the nonwoven fabric of the present invention can be used by cutting into a tape shape having a width of 30 to 50 mm, for example, from the viewpoint of processing efficiency and stability with respect to the size of the hard disk. .
Then, while the substrate is continuously rotated, the cleaning cloth or substrate is reciprocated in the radial direction of the substrate while pressing the cleaning cloth in the form of tape on the polished substrate, and the cleaning cloth is continuously moved. To run. At this time, a method of supplying an aqueous solution of water and / or an organic acid cleaning agent to the surface of the cleaning cloth and cleaning the substrate surface with ultrafine fibers on the surface is preferable.

  The organic acid cleaning agent used here preferably contains at least one of sulfonic acid, citric acid, malic acid and acetic acid. As a cleaning method, the magnetic recording disk substrate made of glass or the like can be cleaned using the cleaning tape and the cleaning agent as described above.

[Measuring method and processing method for evaluation]
EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition, the process used for measurement and evaluation of each physical property is based on the following method.

(1) Melting point Using DSC-7 manufactured by Perkin Elmer, the peak top temperature at which the polymer melted at 2nd run was defined as the melting point of the polymer. At this time, the rate of temperature increase was 16 ° C./min, and the sample amount was 10 mg.

(2) Melt flow rate (MFR)
4-5 g of sample pellets are placed in a cylinder of an MFR meter electric furnace, and a resin made of Toyo Seiki Seisakusho Co., Ltd., melt indexer (S101), is used for 10 minutes under a load of 2160 gf and a temperature of 285 ° C. Mass (g) was measured. The same measurement was repeated 3 times, and the average value was defined as MFR.

(3) Measurement of the number of fiber diameter peaks of ultrafine fibers A cross section perpendicular to the thickness direction including the ultrafine fibers of a sheet-like material is 3000 times using a scanning electron microscope (SEM, manufactured by Keyence Corporation, model VE-7800). Observe and extract one ultrafine fiber bundle that can be observed within a 30 μm × 30 μm field of view, measure the diameter of all the single fibers constituting the ultrafine fiber bundle in μm units, each with three significant figures, and round off to be effective Obtained with two digits. However, this was done at 10 locations. When the ultrafine fiber had an irregular cross section, first, the cross sectional area of the single fiber was measured, and the diameter of the single fiber was calculated by calculating the diameter when the cross section was assumed to be circular. The single fiber diameter thus obtained was further rounded to the second decimal place to obtain a unit of 0.1 μm, and then a frequency distribution of the fiber diameter distribution was created in increments of 0.1 μm. When this frequency distribution was graphed as a straight line or a curve, the upwardly convex point was defined as the peak of the fiber diameter distribution, the fiber diameter at that time was determined in units of 0.1 μm, and the number was counted. At this time, when another peak is present in the range of the center value of one peak + 30%, the higher frequency is adopted as the peak, and the other is not counted as a peak. Moreover, when both frequency was equal, the average value of each peak center value was employ | adopted as a peak center value.

(4) Measurement of the number of ultrafine fibers From the center value of each peak determined in (3) above, the number of ultrafine fibers existing within the range of the peak center value ± 30% was measured, and the total of these excluding the overlapping portion The ratio of the number of fibers to the total number of fibers was calculated.

(5) Polishing The leather-like sheet material having the nonwoven fabric of the present invention was used as a 30 mm wide tape and used as a polishing cloth. As a polishing target, a substrate made of amorphous glass manufactured by Konica Minolta Glass Tech Co., Ltd., whose surface roughness was controlled to 0.2 nm or less was used. In order to polish both surfaces of the substrate at once, the above tape-like polishing cloth was set on both surfaces of the substrate, and single crystal diamond particles having a primary particle diameter of 1 to 10 nm were clustered to an average diameter of 50 nm on the surface of the cleaning cloth. An abrasive containing 0.01% of free abrasive grains is dropped on both sides at 15 mL / min, the pressure of pressing the tape against the substrate is 1000 g, the substrate rotation speed is 400 rpm, the substrate swinging frequency is 5 Hz, and the tape running speed Polishing was performed at 2.5 cm / min for 10 seconds.

(6) Cleaning process Using the tape-like leather-like sheet-like material as a cleaning cloth, the substrate immediately after the polishing process is replaced with a cleaning agent (Sanyo Chemical Co., Ltd., Chemiclean PR-122), The tape was washed under the same conditions as in the polishing process except that the pressing pressure of the cloth for cleaning with a tape was 750 g and the processing time was 30 seconds, and washed with running water.

(7) Number of errors A magnetic layer was formed on the glass substrate after the cleaning process, and the incidence of defective disks due to foreign matters remaining on the substrate surface, such as magnetic defects and error defects, was calculated. The measurement was performed for a total of 3 sets, with 100 discs as one set. For each set, the defective disk occurrence rate due to foreign matter on the disk surface was calculated, and the average value of the occurrence rates in the three sets was defined as the defective disk occurrence rate. When the defective disk occurrence rate is 1% or less, the workability is good, and when it exceeds 1%, the workability is bad.

[Example 1]
(Sea component and island component of raw cotton)
Nylon 6 having a melting point of 220 ° C. and an MFR of 58.3 g / 10 min was used as an island component, and a copolymer polystyrene (co-PSt) obtained by copolymerizing 22 mol% of 2-ethylhexyl acrylate having a melting point of 53 ° C. and an MFR of 300 g / 10 min was used as a sea component. did.

(Spinning / drawing)
Uniform distribution between the measuring plate having a plurality of measuring holes to be measured using the island component and the sea component, and the distributing plate having a plurality of distribution holes in the merging groove for joining the discharged polymer flow from the plurality of measuring holes Using a 400 island / hole sea-island type composite die that can produce two types of ultrafine fibers with different fiber diameters by joining 8 parts of each polymer stream 8 parts each, Melt spinning was carried out under the conditions of a temperature of 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 1.2 g / min / hole, and a spinning speed of 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and single fiber fineness is 3.6 dtex, fiber A raw cotton of a sea-island type composite fiber having a length of 51 mm was obtained.

(Nonwoven fabric)
A laminated fiber web was formed through the carding process and the cross wrapping process using the raw cotton of the above-mentioned sea-island type composite fibers. Next, the obtained laminated fiber web was subjected to a needle depth of 8 mm and the number of punches using a needle punch machine in which one needle having a throat depth of 60 μm, a kick-up of 0 μm, an undercut angle of 27 degrees, and a throat length of 0.8 mm was implanted. Needle punching was performed at 3200 pieces / cm ² , and an ultrafine fiber generating nonwoven fabric having a basis weight of 710 g / m ² and an apparent density of 0.223 g / cm ³ was produced. The ultrafine fiber generating nonwoven fabric was subjected to hot water shrinkage treatment at a temperature of 95 ° C., and then 34% by mass of polyvinyl alcohol was added to the fiber mass, and then dried. Next, this ultrafine fiber generation type nonwoven fabric was impregnated with trichlorethylene and subjected to ultrafine fiber generation processing for dissolving and removing sea components to obtain a nonwoven fabric composed of ultrafine fibers.

(Leather-like sheet)
The non-woven fabric obtained as described above is provided with a polyurethane having a polymer diol of 75% by mass of a polyether and 25% by mass of a polyester based on a solid content of 31% by mass with respect to the fiber mass, and a liquid temperature of 35 ° C. The polyurethane was coagulated with a 30% aqueous DMF solution and treated with hot water at a temperature of about 85 ° C. to remove DMF and polyvinyl alcohol. Thereafter, the sheet was cut in the thickness direction by a half-cutting machine having an endless band knife. Using the JIS # 320 sandpaper, the non-semi-finished surface of the obtained sheet is advanced in the opposite direction to the rotation of the sandpaper, and is ground by three-stage buffing at a sheet speed of 5 m / min. A leather-like sheet-like material of Example 1 was prepared.

The obtained leather-like sheet-like material of Example 1 has napped fibers with ultrafine fibers whose centers of two fiber diameter distribution peaks are 0.3 μm and 0.9 μm, and has a thickness of 0.55 mm. Was 185 g / m ² and the apparent density was 0.336 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of both peaks accounted for 97.9% of the total number.
Using the leather-like sheet-like material of Example 1 thus obtained, polishing and cleaning were performed, and error performance evaluation was performed. As a result, the defective disk occurrence rate was 0.5% and the workability was good. It was satisfying. The results are shown in Table 1.

[Example 2]
(raw cotton)
Using the same island component and sea component as used in Example 1, four pieces of the polymer flow of the island component are merged by four at the merge plate, so that the number of two types of ultrafine fibers having different fiber diameters is obtained. Using a 36 island / hole sea-island type composite die that can be produced at a ratio of 1: 1, a spinning temperature of 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 2.1 g / min / hole, and a spinning speed of 1240 m / min. The melt spinning was performed under the following conditions. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and single fiber fineness is 6.6 dtex, fiber A raw cotton of a sea-island type composite fiber having a length of 51 mm was obtained.

(Nonwoven fabric and leather-like sheet)
In the same manner as in Example 1, an ultrafine fiber-generating nonwoven fabric having a basis weight of 650 g / m ² and an apparent density of 0.230 g / cm ³ was prepared, and an ultrafine fiber generation process was performed to obtain a nonwoven fabric composed of ultrafine fibers. Thereafter, in the same manner as in Example 1, the leather-like sheet of Example 2 was obtained.
The obtained leather-like sheet-like material of Example 2 has naps of ultrafine fibers whose centers of two fiber diameter distribution peaks are 1.8 μm and 3.6 μm, has a thickness of 0.52 mm, and a basis weight. Was 182 g / m ² and the apparent density was 0.350 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of both peaks accounted for 94.5% of the total number.
Using the obtained leather-like sheet-like material of Example 2, polishing processing and cleaning processing were performed, and error performance evaluation was performed. The defective disk occurrence rate was 0.6% and the workability was good. Although it was slightly worse than Example 1, it was satisfactory. The results are shown in Table 1.

[Example 3]
(raw cotton)
The same island component and sea component used in Example 1 are used, and four of the polymer flows of the island component are merged by four at the merge plate, and the other part is merged by eight, thereby producing fibers. Using a 480 island / hole sea-island type composite die capable of producing three types of ultrafine fibers with different diameters at a 1: 1: 1 ratio, a spinning temperature of 280 ° C., an island / sea mass ratio of 40/60, and a discharge rate The melt spinning was performed under the conditions of 1.4 g / min · hole, spinning speed 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and single fiber fineness is 4.4 dtex, fiber A raw cotton of a sea-island type composite fiber having a length of 51 mm was obtained.

(Nonwoven fabric and leather-like sheet)
In the same manner as in Example 1, an ultrafine fiber-generating nonwoven fabric having a basis weight of 720 g / m ² and an apparent density of 0.221 g / cm ³ was prepared, and an ultrafine fiber generation process was performed to obtain a nonwoven fabric composed of ultrafine fibers. After that, the leather-like sheet of Example 3 was obtained in the same manner as Example 1.
The obtained leather-like sheet of Example 3 has naps of ultrafine fibers whose centers of the three fiber diameter distribution peaks are 0.3 μm, 0.6 μm and 1.0 μm, and the thickness is 0 It was 0.55 mm, the basis weight was 185 g / m ² , and the apparent density was 0.336 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of each peak accounted for 95.7% of the total number.
Using the leather-like sheet-like material of Example 3 obtained, polishing and cleaning were performed, and error performance evaluation was performed. As a result, the defective disk occurrence rate was 0.4% and the workability was good. The result was better than Example 1. The results are shown in Table 1.

[Example 4]
(raw cotton)
The same island component and sea component used in Example 1 are used, and a part of the polymer stream of the island component is merged by four at the merge plate, the other part is merged by eight, and another Using a 120 island / hole sea-island type composite die that can produce four types of ultrafine fibers with different fiber diameters by 1: 1: 1: 1 by merging 64 parts of each part, spinning Melt spinning was performed under the conditions of a temperature of 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 1.7 g / min · hole, and a spinning speed of 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and single fiber fineness is 5.3 dtex, fiber A raw cotton of a sea-island type composite fiber having a length of 51 mm was obtained.

(Nonwoven fabric and leather-like sheet)
In the same manner as in Example 1, an ultrafine fiber generating nonwoven fabric having a basis weight of 700 g / m ² and an apparent density of 0.222 g / cm ³ was prepared, and an ultrafine fiber generating process was performed to obtain a nonwoven fabric composed of ultrafine fibers. After that, a leather-like sheet of Example 4 was obtained in the same manner as Example 1.
The obtained leather-like sheet-like material of Example 4 has napped fibers with ultrafine fibers whose centers of four fiber diameter distribution peaks are 0.3 μm, 0.6 μm, 1.0 μm, and 2.7 μm, The thickness was 0.53 mm, the basis weight was 185 g / m ² , and the apparent density was 0.349 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of each peak accounted for 94.7% of the total number.
Using the leather-like sheet-like material of Example 4 obtained, polishing and cleaning were performed, and error performance evaluation was performed. As a result, the defective disk occurrence rate was 0.2% and the workability was good. The numerical value was slightly better than Example 1. The results are shown in Table 1.

[Example 5]
(raw cotton)
Using the same island component and sea component as used in Example 1, a part of the polymer stream of the island component is joined by four at the junction plate, the other part is joined by 16 pieces, and another 5 types of ultrafine fibers having different fiber diameters can be produced at a ratio of 1: 1: 1: 1: 1 by merging 64 portions and merging each other portion by 128. Using an island / hole sea-island type composite die, melt spinning was performed at a spinning temperature of 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 2.0 g / min / hole, and a spinning speed of 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and has a fineness of 6.2 dtex and a fiber length of A 51 mm sea-island composite fiber raw cotton was obtained.

(Nonwoven fabric and leather-like sheet)
In the same manner as in Example 1, an ultrafine fiber-generating nonwoven fabric having a basis weight of 710 g / m ² and an apparent density of 0.228 g / cm ³ was prepared, and an ultrafine fiber generation process was performed to obtain a nonwoven fabric composed of ultrafine fibers. After that, a leather-like sheet of Example 5 was obtained in the same manner as Example 1.
The obtained leather-like sheet-like material of Example 5 has napped fibers with ultrafine fibers whose centers of the five fiber diameter distributions are 0.3 μm, 0.7 μm, 1.3 μm, 2.6 μm and 3.7 μm. The thickness was 0.54 mm, the basis weight was 180 g / m ² , and the apparent density was 0.333 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of each peak accounted for 96.5% of the total number.
Using the leather-like sheet-like material of Example 5 thus obtained, polishing and cleaning were carried out, and error performance evaluation was carried out. As a result, the defective disk occurrence rate was 0.1% and the workability was even better. There was a good numerical value as compared with Example 1. The results are shown in Table 1.

[Example 6]
(raw cotton)
Using the same island component and sea component as used in Example 1 and using a 450 island / hole sea-island type composite die capable of producing an island component of one type of ultrafine fiber having approximately the same fiber diameter, spinning temperature Melt spinning was performed at 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 0.7 g / min / hole, and a spinning speed of 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and the fineness is 2.2 dtex and the fiber length is A 51 mm sea-island composite fiber raw cotton was obtained.
Furthermore, using the above-mentioned island component and sea component, using an 18 island / hole sea-island composite base that can produce one type of ultra-fine fiber that is different from the above-mentioned ultra-fine fiber in the fiber diameter. The melt spinning was carried out under the conditions of a spinning temperature of 280 ° C., an island / sea mass ratio of 40/60, a discharge amount of 1.3 g / hole, and a spinning speed of 1240 m / min. Subsequently, the same drawing conditions as above were applied to obtain a second raw cotton having a fineness of 4.0 dtex and a fiber length of 51 mm.

(Nonwoven fabric and leather-like sheet)
Ultrafine fiber having a basis weight of 750 g / m ² and an apparent density of 0.233 g / cm ^{3 in} the same manner as in Example 1 except that the above two types of sea-island composite fibers were blended at a mass ratio of 1: 1. A generation type non-woven fabric was prepared and subjected to ultra-fine fiber generation processing to obtain a non-woven fabric composed of ultra-fine fibers, and then a leather-like sheet material of Example 6 was obtained in the same manner as Example 1.
The obtained leather-like sheet-like material of Example 6 has naps of ultrafine fibers whose centers of two fiber diameter distribution peaks are 0.5 μm and 3.1 μm, and has a thickness of 0.55 mm. Was 184 g / m ² and the apparent density was 0.345 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of each peak accounted for 96.6% of the total number.
Using the obtained leather-like sheet-like material of Example 6, polishing and cleaning were performed, and error performance evaluation was performed. As a result, the defective disk occurrence rate was 0.8% and the workability was good. Although it was a slightly worse value compared with Example 1, it was a satisfactory result. The results are shown in Table 1.

[Example 7]
(raw cotton)
Using the same island component and sea component used in Example 1, 64 pieces of polymer flow of island components are merged by 64 at the merge plate, so that the number of two types of ultrafine fibers having different fiber diameters is the number. Using a 120 island / hole sea-island type composite die that can be produced at a ratio of 1: 1, a spinning temperature of 280 ° C., an island / sea mass ratio of 30/70, a discharge rate of 0.8 g / min / hole, and a spinning speed of 1240 m / min. The melt spinning was performed under the following conditions. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and single fiber fineness is 2.4 dtex, fiber A raw cotton of a sea-island type composite fiber having a length of 51 mm was obtained.

(Nonwoven fabric and leather-like sheet)
In the same manner as in Example 1, an ultrafine fiber-generating nonwoven fabric having a basis weight of 800 g / m ² and an apparent density of 0.220 g / cm ³ was prepared, and an ultrafine fiber generation process was performed to obtain a nonwoven fabric composed of ultrafine fibers. Thereafter, in the same manner as in Example 1, the leather-like sheet of Example 7 was obtained.
The obtained leather-like sheet-like material of Example 7 has napped fibers of ultrafine fibers whose centers of two fiber diameter distribution peaks are 0.2 μm and 1.3 μm, and has a thickness of 0.51 mm. Was 180 g / m ² and the apparent density was 0.353 g / cm ³ . The total number of fibers included in the range of the center value ± 30% of both peaks accounted for 98.2% of the total number.
Using the obtained leather-like sheet-like material of Example 7, polishing and cleaning were performed, and error performance evaluation was performed. The defect disk occurrence rate was 0.3% and the workability was good. It was satisfactory. The results are shown in Table 1.

[Example 8]
(raw cotton)
Using the same island component and sea component as used in Example 1 and using a sea island type composite base of 2500 islands / hole that can produce one type of ultrafine fiber having almost the same fiber diameter, spinning temperature Melt spinning was performed at 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 1.1 g / min / hole, and a spinning speed of 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and the fineness is 3.3 dtex and the fiber length is A 51 mm sea-island composite fiber raw cotton was obtained.
(Nonwoven fabric and leather-like sheet)
The basis weight is 780 g / m ² and the apparent density is the same as in Example 1 except that the sea-island type composite fiber and the second raw cotton obtained in Example 6 are mixed at a mass ratio of 1: 1. After producing a 0.232 g / cm ³ ultrafine fiber-generating nonwoven fabric and performing ultrafine fiber generation processing to obtain a nonwoven fabric composed of ultrafine fibers, the leather-like sheet of Example 8 was obtained in the same manner as Example 1. A product was obtained.
The obtained leather-like sheet of Example 8 has naps of ultrafine fibers whose center of the two fiber diameter distribution peaks are 0.2 μm and 3.1 μm, has a thickness of 0.55 mm, and a basis weight. Was 189 g / m 2 and the apparent density was 0.344 g / cm 3. The total number of fibers included in the range of the center value ± 30% of each peak accounted for 97.1% of the total number.
Using the leather-like sheet-like material of Example 8 obtained, polishing and cleaning were performed, and error performance evaluation was performed. The defective disk occurrence rate was 0.7% and the workability was good. It was a satisfactory result. The results are shown in Table 1.

[Comparative Example 1]
(raw cotton)
Using the same island component and sea component as used in Example 1 and using a 450 island / hole sea-island type composite die capable of producing an island component of one type of ultrafine fiber having approximately the same fiber diameter, spinning temperature Melt spinning was performed at 280 ° C., an island / sea mass ratio of 40/60, a discharge rate of 0.7 g / min / hole, and a spinning speed of 1240 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, and the fineness is 2.2 dtex and the fiber length is A 51 mm sea-island composite fiber raw cotton was obtained.

(Nonwoven fabric and leather-like sheet)
Except for using the raw cotton of the above-mentioned sea-island type composite fiber, after creating an ultrafine fiber generation type nonwoven fabric in the same manner as in Example 1, and performing ultrafine fiber generation processing to obtain a nonwoven fabric composed of ultrafine fibers, In the same manner as in Example 1, a leather-like sheet material of Comparative Example 1 was obtained.
The obtained leather-like sheet-like material of Comparative Example 1 has napped fibers having a single fiber diameter distribution at 0.5 μm, a thickness of 0.55 mm, a basis weight of 181 g / m ² , and an appearance. The density was 0.329 g / cm ³ . The total number of fibers included in the range of the above peak center value ± 30% accounted for 97.0% of the total number.
Using the leather-like sheet-like material of Comparative Example 1 obtained, polishing and cleaning were performed, and error performance evaluation was performed. The defective disk occurrence rate was 1.2% and the workability was poor. It became a bad value compared with any of Examples 1-8 of the present invention. The results are shown in Table 1.

[Comparative Example 2]
(raw cotton)
(Sea component and island component)
Using the same island component and sea component as used in Example 1 and using an 18 island / hole sea-island composite die capable of producing one type of ultrafine fiber having substantially the same fiber diameter, a spinning temperature of 280 Melt spinning was carried out under the conditions of ° C, an island / sea mass ratio of 40/60, a discharge rate of 1.3 g / hole, and a spinning speed of 1240 m / min. Next, the same drawing conditions as in Example 1 were applied to obtain a sea-island composite fiber raw cotton having a fineness of 4.0 dtex and a fiber length of 51 mm.

(Nonwoven fabric and leather-like sheet)
Except for using the raw cotton of the above-mentioned sea-island type composite fiber, after creating an ultrafine fiber generation type nonwoven fabric in the same manner as in Example 1, and performing ultrafine fiber generation processing to obtain a nonwoven fabric composed of ultrafine fibers, In the same manner as in Example 1, the leather-like sheet material of Comparative Example 2 was obtained.
The obtained leather-like sheet-like material of Comparative Example 2 has naps of ultrafine fibers having one fiber diameter distribution peak at 3.1 μm, a thickness of 0.53 mm, a basis weight of 187 g / m ² , and an appearance. The density was 0.353 g / cm ³ . The total number of fibers included in the range of the above peak center value ± 30% accounted for 98.0% of the total number.
Using the leather-like sheet material of Comparative Example 2 obtained, polishing and cleaning were performed, and error performance evaluation was performed. As a result, the defective disk occurrence rate was 3.9%, and the workability was poor. Compared with Examples 1 to 8 of the present invention, the values were significantly worse. The results are shown in Table 1.

[Comparative Example 3]
(raw cotton)
The same island component and sea component used in Example 1 are mixed by 50% by weight, and the island component is mixed in the sea component by a so-called mixed spinning method in which sea-island fiber is melt-spun at a spinning temperature of 280 ° C. About 1000 ultrafine fiber-generating fibers were melt spun at a spinning speed of 1000 m / min. Next, it is stretched 3.0 times in an oil solution bath for spinning at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, fineness is 9.8 dtex, fiber length Was obtained as a raw cotton of a sea-island type composite fiber having a thickness of 51 mm.

(Nonwoven fabric and leather-like sheet)
Except for using the raw cotton of the above-mentioned sea-island type composite fiber, after creating an ultrafine fiber generation type nonwoven fabric in the same manner as in Example 1, and performing ultrafine fiber generation processing to obtain a nonwoven fabric composed of ultrafine fibers, In the same manner as in Example 1, the leather-like sheet material of Comparative Example 3 was obtained.
The obtained leather-like sheet of Comparative Example 3 has napped fibers of ultrafine fibers having one fiber diameter distribution peak at 0.8 μm, a thickness of 0.55 mm, and a basis weight of 195 g / m ² . The density was 0.355 g / cm ³ . The total number of fibers included in the range of the above peak center value ± 30% accounted for 66.8% of the total number of fibers.
Using the leather-like sheet-like material of Comparative Example 3 obtained, polishing and washing were performed, and error performance evaluation was performed. The defective disk occurrence rate was 4.5%, and the workability was poor. Compared with Examples 1 to 8 of the present invention, the values were significantly worse. The results are shown in Table 1.

[Comparative Example 4]
(raw cotton)
Using the same island component and sea component used in Example 1, raw cotton obtained in the same manner as in Comparative Example 2 and second raw cotton obtained in the same manner as in Comparative Example 3 were used.

(Nonwoven fabric and leather-like sheet)
The basis weight is 800 g / m ² and the apparent density is 0.239 g / cm ^{3 in the same} manner as in Example 1 except that the raw cotton of the above two types of sea-island type composite fibers is blended at a mass ratio of 1: 1. After producing an ultrafine fiber generation type nonwoven fabric and performing an ultrafine fiber generation process to obtain a nonwoven fabric composed of ultrafine fibers, a leather-like sheet material of Comparative Example 4 was obtained in the same manner as in Example 1.
The obtained leather-like sheet-like material of Comparative Example 4 has napped fibers of ultrafine fibers whose centers of two fiber diameter distribution peaks are 0.8 μm and 3.1 μm, and has a thickness of 0.54 mm. Was 189 g / m ² and the apparent density was 0.350 g / cm ³ . The total number of fibers included in the range of both peak center values ± 30% described above accounted for 75.3% of the total number of fibers.
Using the leather-like sheet material of Comparative Example 4 obtained, polishing and cleaning were performed, and error performance evaluation was performed. As a result, the defective disk occurrence rate was 2.8% and the workability was poor. It became a bad value compared with Examples 1-8 of the present invention. The results are shown in Table 1.

  The non-woven fabric, leather-like sheet-like material, and washed cloth described in each of the above-described examples are examples for embodying the technical idea of the present invention. The value, the material and manufacturing method of the ultrafine fiber, the material and ratio of the elastic polymer, etc. are not limited to those of the above embodiments and examples, and various modifications are made within the scope of the claims of the present invention. To get.

For example, in the above-described embodiments, sea-island type composite fibers are used as the ultrafine fiber generating fibers, but in the present invention, ultrafine fiber generating fibers having other structures such as peelable composite fibers may be used.
Further, in the above-described embodiment, a fiber entangled nonwoven fabric in which fibers are entangled by a needle punch is used. However, in the present invention, a fiber entangled nonwoven fabric by water jet punch may be used, or a nonwoven fabric obtained by a spunbond method, a melt blow method, a papermaking method, or the like may be used.
Needless to say, the materials constituting the ultrafine fibers and the elastic polymer are not limited to those of the above embodiments.

  The nonwoven fabric of the present invention and the leather-like sheet-like material and cleaning cloth using the same can effectively remove foreign substances widely distributed from several tens of nm to several μm, so the surface of the magnetic recording medium substrate is washed. Particularly suitable as a cleaning cloth to be used, but as a high-performance polishing cloth using free abrasive grains such as diamond abrasive grains, it can be preferably used for tape polishing, and also includes a wiping cloth, various abrasives, a filter, It is also suitably used for industrial material applications such as hazardous substance removal products.

Claims (4)

The distribution created in 0.1 μm increments of the fiber diameter has at least one peak center value in the range of 0.10 to 1.0 μm and at least one peak center value in the range of 1.0 to 5.0 μm. the provided, the center value of the peak located at a larger diameter side, 1.3 times greater than the center value of the peak adjacent to the small diameter side, and within range of the center value ± 30% of each peak A non-woven fabric for polishing and cleaning hard disks, wherein the total number of fibers occupies 90% or more of the total number of fibers. The above fibers one from sea-island type composite fiber to generate a thickness of different fibers from each other from the composite fibers of polishing and cleaning process for nonwoven hard disk according to claim 1. A leather-like sheet-like product comprising the non-woven fabric for polishing and cleaning hard disks according to claim 1 or 2 , wherein an elastic polymer is contained inside the non-woven fabric. The leather-like sheet-like material according to claim 3 , wherein the leather-like sheet-like material is a washed cloth.

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