JP2008240168A - Fiber structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber structure not only enabling abrasive grain to be utilized efficiently but also enabling polishing to be carried out with very little defects such as scratch when used as an abrasive cloth, and useful as the abrasive cloth having excellent smoothness and polishing rate. <P>SOLUTION: The fiber structure having a surface layer substantially consisting of fiber has ≤2 cc/cm<SP>2</SP>/sec air permeability. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY When used as an abrasive cloth, the present invention is useful as an abrasive cloth excellent in smoothness and polishing rate, capable of efficiently using abrasive grains and capable of polishing with very few defects such as scratches. It relates to a fiber structure. More specifically, the present invention relates to a fiber structure that can be suitably used for a wiping cloth such as a wiping cloth for glasses, a hard disk, a silicon wafer, an integrated circuit board, precision equipment, an abrasive cloth or a cleaning tape used in a manufacturing process of optical parts, etc. .

  Hard disks, silicon wafers, integrated circuit boards, precision instruments, and optical components have increasingly required performance, and accordingly, further precision of substrate surface processing is required. Specifically, the high precision of the substrate surface processing here is mainly to improve the smoothness of the substrate surface and to reduce scratches. As a means for solving these problems, for example, ultrafine fibers (micron level) are used. There have been proposed polishing cloths made of woven fabric (for example, see Patent Document 1) or non-woven fabric (for example, see Patent Document 2). By using ultrafine fibers, the force applied to the abrasive grains is dispersed, and the aggregation of abrasive grains that cause scratches and the generation of abrasive debris are suppressed. There is a need for improvement.

  In addition, a polishing cloth using nanofibers as even thinner fibers has been proposed, but in this case as well as in the case of wiping cloth, the nanofibers are bundled and the original fiber diameter is fully utilized. It is not clear and sufficient effect is not acquired.

  In addition, a polishing pad made of a resin such as polyurethane having micropores inside, and a polishing pad made by impregnating a nonwoven fabric made of a fiber having a relatively large fiber diameter with a resin such as polyurethane have been proposed (for example, patents). Reference 3), no smoothness of the polished surface, few defects such as scratches, and polishing efficiency are not obtained.

Such a polishing pad has a structure in which a large proportion of holes occupy the surface for the purpose of discharging polishing scraps and aggregated abrasive grains generated by polishing, and such a structure is suitable for discharging polishing scraps and aggregated abrasive grains. On the other hand, the abrasive grains necessary for polishing are also discharged at the same time, so that there is a problem that the use efficiency of the abrasive grains is low.
JP-A-11-90810 JP 2003-236739 A JP-A-3-234475

  An object of the present invention is to eliminate the above-mentioned problems of the prior art, and when used as a polishing cloth, it is possible to efficiently use abrasive grains and perform polishing with very few defects such as scratches. Another object of the present invention is to provide a fiber structure useful as an abrasive cloth excellent in smoothness and polishing rate.

In order to solve the above problems, the present invention has the following configuration. That is,
(1) A fiber structure comprising substantially only fibers, wherein the air permeability is ² cc / cm ² / sec or less.

  (2) The fiber structure according to (1), wherein a number average fiber diameter of fibers constituting the fiber structure is 1 μm or less.

  (3) The fiber structure according to (1) or (2), wherein a concave portion is formed on the surface.

(4) The fiber structure according to any one of (1) to (3), wherein the air permeability of the surface layer is ² cc / cm ² / sec or less.

  (5) The fiber structure according to any one of (1) to (4), wherein a through hole is formed.

  (6) The fiber structure according to any one of (1) to (4) and at least one selected from the group consisting of another fiber structure, a plate-like body, and a film are combined and integrated. The laminated fiber structure characterized by the above-mentioned.

  (7) The laminated fiber structure according to claim 6, wherein a through-hole is formed.

  When the fiber structure of the present invention is used as an abrasive cloth, the abrasive grains are gripped by the surface of the abrasive cloth during the polishing and do not move to the inner layer of the abrasive cloth, so that the abrasive grains can be used effectively, so that the abrasive structure can be used efficiently. Polishing can be performed. Moreover, since it consists essentially of fibers, even if coarse particles such as polishing debris and agglomerated abrasive grains are present, the polishing load is dispersed and scratches are unlikely to occur. Furthermore, since the polishing cloth itself is excellent in smoothness, the surface smoothness of the object to be polished obtained by polishing is also very excellent. When used in a wiping cloth or the like, the wiping performance is excellent, and a high-performance fiber structure with little wiping residue can be provided.

The fiber structure of the present invention is a fiber structure substantially consisting of only fibers, and has an air permeability of ² cc / cm ² / sec or less.

  The term “substantially composed only of fibers” as used herein indicates that a resin such as a polymer elastic body is not substantially exposed between the fibers when observed by an SEM photograph or the like.

  Therefore, the polymer elastic body may be included in the fiber structure as long as the effect of the present invention is not impaired, but it is preferably not included because it may be exposed on the surface. As a result, it is possible to suppress the occurrence of scratches caused by the falling off or exposure of the resin.

  Further, when fibers are dropped by polishing, scratches may occur due to the fibers, and therefore, the fibers on the surface are preferably intertwined or fused. In particular, in the surface layer portion within a range of 0.3 mm from the surface, the fibers do not form fiber bundles, and having a structure in which the fibers are entangled with each other suppresses fiber dropping and improves surface smoothness. preferable.

  In this invention, since it consists only of fiber and the fiber is not being fixed with resin, the freedom degree of movement of a fiber is very high. Therefore, when it is used as a polishing cloth, a load is uniformly applied to the abrasive grains, so that polishing with high smoothness and few defects such as scratches can be performed.

Moreover, the value measured based on the method (fragile type method) prescribed | regulated to JISL-1096 is used for the air permeability of this invention. As will be described later, a fiber structure in which a concave portion is formed on the surface of the fiber structure of the present invention is one of the preferred embodiments of the present invention. Depending on the depth and shape of the recess, air may easily pass through the recess and the apparent air permeability may increase. In such a case, it is important that the air permeability of the portion having no recess is ² cc / cm ² / sec or less. Therefore, the air permeability of the part from which the recesses are removed or the air permeability of the fiber structure before forming the recesses is measured, and the value is taken as the air permeability of the fiber structure. Moreover, when the woven or knitted fabric or film is bonded to the back surface of the fiber structure, the measurement is performed in a state in which they are removed.

It is important that the fiber structure of the present invention has an air permeability measured by the above method of ² cc / cm ² / sec or less. Here, the low air permeability means that the density of the fiber structure is small and the gaps between the fibers are small, in particular, there are few large gaps. That is, with such a low air permeability structure, the abrasive grains do not move to the inner layer of the fiber structure during polishing, but remain on the surface, so that efficient polishing can be performed. Conventionally, foamed polyurethane, nonwoven fabric impregnated with polyurethane, woven or knitted fabrics have been used as abrasive cloths, but in these abrasive cloths, if the air permeability is low, aggregated abrasive grains and polishing debris cannot be discharged Although a technology for increasing the air permeability by increasing the pores of the foam structure and the fiber gap has been known (for example, JP-A-2001-198797) There was no idea of obtaining a polishing cloth. Since the present invention is substantially made of only fibers, even if agglomerated abrasive grains and polishing scraps are present, since the degree of freedom of movement of the fibers is high and excessive load is dispersed, it is difficult to generate scratches. The present inventors have found that there is no large fiber gap and have reached the present invention.

  In such a fiber structure with low air permeability, it is important that the fibers in the surface layer are present in a dense state with very small voids between the fibers.

In the present invention, it is further important that the air permeability of the surface layer of the fiber structure is low, and the air permeability of the surface layer is preferably ² cc / cm ² / sec or less. The air permeability of the surface layer here is measured as follows.

  If the thickness of the fiber structure exceeds 0.3 mm, adjust the thickness of the fiber structure by grinding such as slicing or buffing, and prepare the sample so that the thickness of the fiber structure on the surface layer side is 0.3 mm. The value adjusted and measured based on the method (fragile type method) prescribed in JIS L-1096 is used. In this case, it should be ensured that the fiber structure is damaged and that there are no holes or extremely thin portions. Further, when the thickness of the fiber structure is 0.3 mm or less, the air permeability measured without performing the slicing or grinding is used as the air permeability of the surface layer. In addition, as will be described later, when the fiber structure of the present invention and other fiber structures, plate-like bodies, films, etc. are combined and integrated, other composite fiber structures, plate-like bodies, films, etc. The air permeability is measured after peeling or grinding.

  The fiber structure of the present invention consists essentially of fibers, and in order to lower the air permeability, it is important that the surface of the fiber structure is densely covered with fibers. For this reason, the fibers constituting the surface are preferably so-called ultrafine fibers having a small fiber diameter. Specifically, the number average fiber diameter of such fibers is preferably 1 μm or less. Here, the number average diameter of the fibers is obtained by observing the surface of the fiber structure with a transmission electron microscope (TEM) or a scanning electron microscope (SEM), and measuring the diameters of 30 single fibers randomly extracted within the same surface. Further, sampling is performed 10 times, and a simple average value is obtained from data of a total of 300 single fiber diameters, and this is set as a number average fiber diameter in the present invention.

  Further, the number average fiber diameter is more preferably 500 nm or less, and further preferably 200 nm or less. In addition, when the fiber is too thin, the fiber is cut due to insufficient strength, and the cut fiber causes dirt and scratches. Therefore, the number average fiber diameter is preferably 10 nm or more, and more preferably 50 nm or more. Furthermore, in the present invention, it is important to fix the fibers so that the fibers on the surface do not fall off without using a binder such as a resin. As such immobilization means, partial fusion by heat or pressure or fiber entanglement is effective. However, as the fiber diameter is thinner, these means not only work effectively, but the fiber diameter is narrower. Then, the cohesive force of the fiber itself becomes strong, and the fiber does not fall off without using a special means. From the above viewpoint, ultrafine fibers are preferable.

  As a substance constituting such a fiber, a thermoplastic polymer is preferable from the viewpoint of moldability. Among them, many polycondensation polymers represented by polyester and polyamide are more preferable because they have a high melting point. Moreover, it is preferable that the melting point of the polymer, which becomes a fiber that develops after removing at least one of the polymers having different solubilities described later, is 165 ° C. or higher because the heat resistance of the fiber is good. For example, polylactic acid (PLA) is 170 ° C, polyethylene terephthalate (PET) is 255 ° C, and nylon 6 (N6) is 220 ° C. Further, the polymer may contain additives such as particles, a flame retardant, and an antistatic agent. Further, other components may be copolymerized and mixed as long as the properties of the polymer are not impaired.

  The method for producing such fibers is not particularly limited. For example, a method of directly spinning ultrafine fibers, a fiber having a normal fineness and capable of generating ultrafine fibers, a so-called ultrafine fiber generating fiber is spun. Then, it can be produced by a method of generating ultrafine fibers. Examples of the method using the ultrafine fiber generating fiber include a method of removing sea components after spinning the sea-island fiber, and a method of spinning the split-type fiber and then splitting it to make it ultrafine. Among these, in the present invention, it is preferable to manufacture with an island-in-sea fiber or a split-type fiber, and more preferable to manufacture with an island-in-sea fiber, from the viewpoint that ultrafine fibers can be obtained easily and stably.

  The sea-island fiber referred to in the present invention refers to a fiber in which two or more components are combined and mixed at any stage to obtain a sea-island state, and the method for obtaining this fiber is not particularly limited. For example, (1) A method of blending and spinning two or more polymers in a chip state, (2) A method of kneading a polymer of two or more components in advance to form a chip and then spinning, (3) A polymer of two or more components in a molten state Examples thereof include a method of mixing with a static kneader in a pack of a spinning machine, and (4) a method of producing using a base such as Japanese Patent Publication Nos. 44-18369 and 54-116417. In the present invention, any of the methods can be successfully produced, but the methods (1) and (2) are excellent in that the fineness of the ultrafine fibers and the dispersibility of the ultrafine fibers when jetting a high-pressure fluid stream are excellent. In particular, the method (2) is preferably employed.

  In the method (2), the cross-sectional shape of the island fiber obtained by removing the sea-island fiber and the sea component is not particularly limited, and the number of polymer species to be used is not particularly limited. Is preferably 2 to 3 components, and particularly preferably composed of 2 components of 1 component of the sea and 1 component of the island. Moreover, it is preferable that the component ratio at this time is 0.1-0.8 by weight ratio with respect to a sea-island type fiber of an island fiber, 0.2-0.6 are more preferable, 0.3-0.5 Is more preferable. If it is less than 0.1, the removal rate of sea components increases, which is not preferable in terms of cost. On the other hand, if it exceeds 0.8, the island components tend to be joined together, which is not preferable in terms of spinning stability.

  In the present invention, it is important that the sea component and the island component have different solubility in water, an alkaline solution, an acidic solution, an organic solvent, and a solvent such as a supercritical fluid. The larger the range that does not affect the other characteristics, the more preferable is the seawater component, so that only the sea component can be selectively removed.

  Such a sea component and island component are kneaded and alloyed into a polymer alloy melt. After spinning, this is cooled and solidified to form a fiber, and if necessary, stretched and heat treated to obtain a sea-island fiber. obtain. In addition to simple single-component round cross-section fibers, such sea-island fiber forms include composite fibers made of different or similar polymers, crimped fibers, deformed cross-section fibers, hollow fibers, false twisted fibers, and the like. It can be appropriately selected depending on the purpose of spun yarn, covering yarn, and strong twisted yarn made of fiber. The above-described fiber structure is formed using the sea-island fiber thus obtained. Moreover, the nonwoven fabric which consists of a sea-island type fiber can also be directly obtained from an alloy melt by the melt blow method or the spun bond method. Moreover, before removing a sea component, or after that, it cuts to the length of about 0.1 mm, and can also obtain paper according to the method of manufacturing paper from a normal pulp.

  After the fiber structure is manufactured, or during the manufacturing process, the sea component is removed to express the ultrafine fiber. As a method of removing the sea component, it is preferable to employ a method of extracting and removing the sea component using a solvent that dissolves the sea component but does not substantially dissolve or hardly dissolve the island component. In particular, a method of producing a short fiber nonwoven fabric with ultrafine fiber-generating fibers using an alkali-degradable sea component, and then treating it with a neutral to alkaline aqueous solution to make it ultrafine is preferable in working environment without using a solvent. . The neutral to alkaline aqueous solution here is an aqueous solution having a pH of 6 to 14, and the agent used is not particularly limited. For example, an aqueous solution containing organic or inorganic salts may be used as long as it exhibits a pH in the above range, such as an alkali metal salt such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, calcium hydroxide, Examples include alkaline earth metal salts such as magnesium hydroxide. Further, if necessary, an amine such as triethanolamine, diethanolamine, monoethanolamine, a weight loss accelerator, a carrier and the like can be used in combination. Of these, sodium hydroxide is preferable in terms of price and ease of handling. Furthermore, it is preferable to subject the fiber structure to the neutral to alkaline aqueous solution treatment described above, and then neutralize and wash as necessary to remove residual chemicals and decomposition products, and then dry.

  The fiber structure of the present invention can be obtained, for example, by spraying a high-pressure fluid flow onto the surface of a fiber structure substantially consisting of fibers and dispersing the fibers on the surface to cover the surface.

  Injecting a high-pressure fluid flow here means to make a liquid of 0.1 MPa or more collide with the fiber structure, and the purpose is to monodisperse and open the ultrafine fibers. The liquid used for such treatment is preferably water from the viewpoints of workability, cost, collision energy amount, efficiency, and the like. Other components such as organic solvents, alkalis, acids, dyes, resins, smoothing agents, softeners, silicones, urethanes, and the like mixed in water are also included. The pressure of the high pressure fluid is preferably 0.1 to 20 MPa, more preferably 1 to 10 MPa. If the pressure is low, the dispersion effect of the above-mentioned ultrafine fibers is not sufficient, and if the pressure is too high, the ultrafine fibers fall off during processing or the fiber structure is broken, which is not preferable. Note that the pressure of the fluid flow here refers to the pressure of the fluid inside the nozzle. The nozzle diameter for injecting the high-pressure fluid is 50 to 700 μm, preferably about 100 to 500 μm, and the interval between the nozzles is preferably 1 mm or less. Further, the injection time and the number of times can be arbitrarily selected. In the case of performing a plurality of processes, the pressure and the processing speed can be changed every time the process is performed.

  In addition, before injecting such a high-pressure fluid flow, the fiber structure may be subjected to water immersion treatment. Furthermore, in order to improve the surface quality, a method of relatively moving the nozzle head and the nonwoven fabric, a method of inserting a wire mesh between the nonwoven fabric and the nozzle after entanglement, and a watering treatment can be performed.

  In such treatment, it is preferable that the high-pressure fluid flow is uniformly sprayed on the surface of the fiber structure. Specifically, it is preferable that the cover factor obtained by dividing the surface area of the fiber structure subjected to the water flow by the total surface area of the fiber structure is 80% or more. As a method for increasing the cover factor, it can be achieved by swinging the nozzle head at right angles to the traveling direction of the sheet, arranging the nozzles on a staggered pattern, or processing a plurality of times with nozzles having different patterns. Such a cover factor can be calculated, for example, by the following method.

(1) When nozzles having circular holes arranged in a row are fixed and used When the diameter of the circular holes is R and the pitch of the circular holes (interval between the centers) is P, the cover factor is obtained by the following formula 1. Can do.

(2) When a nozzle having circular holes arranged in a row is used in a swinging manner, the diameter of the circular holes is R, the pitch of the circular holes (interval between the centers) is P, Assuming that the angle formed by the trajectory of the water flow is θ, the cover factor can be obtained by the following equation 2.

  Here, when the swing width is L (mm), the seat traveling speed is S (mm / second), and the swing frequency is C (Hz), the above formula 2 can be obtained by the following formula 3. .

(3) When processing is performed a plurality of times When processing is performed a plurality of times with one row of nozzles, the cover factor for each processing is obtained by the method described above, and the sum of the obtained cover factors is used as the cover factor for the entire processing. Also, if there are holes in multiple rows, such as 2 rows or 3 rows per nozzle, the cover factor is calculated by regarding each row as a single process, and the sum of the obtained cover factors is processed as a whole. Cover factor.

  Moreover, arbitrary temperature from normal temperature to 100 degreeC is applicable for the fluid temperature of a high pressure fluid. It is preferable that the fiber structure is placed on a perforated mesh wire mesh or a drum having an opening, and is run by a transport method such as a belt conveyor and continuously processed. The nozzle can be swung in the length direction or the width direction of the knitted fabric, and not only one side but also double side treatment can be performed.

  As the fiber structure subjected to the above treatment, the following fiber structures can be used. Examples of the knitted fabric include a satin tricot knitted fabric, a rubber knitted fabric, a half tricot knitted fabric, a pile knitted fabric, a flat knitted fabric, and a double-sided knitted fabric, but are not particularly limited thereto. Typical examples of woven fabrics include single, double, triple, multiple texture plain weave, twill, satin weave, double velvet, single / double pile double velvet, double velvet, and chinchilla weave. However, it is not particularly limited to these. Further, as the nonwoven fabric, a nonwoven fabric obtained by a dry method in which a web is obtained using a card, a cross wrapper, or a random web, or a wet method such as a papermaking method can be employed. Moreover, the nonwoven fabric obtained by the method of performing fiber formation and fiber structure formation simultaneously, such as a spun bond method and a melt blow method, can also be employ | adopted.

  In addition, for the purpose of improving strength, cushioning properties, thickness, water retention, etc., it is possible to obtain a laminated fiber structure in which these fiber structures and other fiber structures, plate-like bodies, films, etc. are combined and integrated. . In such a case, the surface on the side that does not become the polished surface does not need to be substantially composed of fibers, and therefore contains the fiber structure alone exemplified above, or polyurethane, melamine resin, polyacrylic resin, or the like. It can be laminated with a fiber structure or a resin plate or film containing no fibers at all. The means for performing such lamination is not particularly limited, but includes a method of bonding using an adhesive, a method of intertwining fiber structures by means of a high-pressure fluid flow or needle punch, and the like. Can be adopted. Moreover, when employ | adopting the spun bond method, the melt blow method, and the electrospinning method, you may form a nonwoven fabric layer as a surface layer directly on the said fiber structure, the fiber structure containing resin, a resin board, and a film.

  The fiber structure of the present invention can be composed of a plurality of layers and can have characteristics according to the purpose. Here, the fiber structure is composed of a plurality of layers means that the fiber structure includes one or more layers composed of the surface layer, the form, and the fibers. By including such a plurality of layers, the surface layer is made of only fibers, and the strength, elasticity, compression characteristics, water permeability, etc. of the entire fiber structure are optimized within a desired range. be able to. For example, cushioning properties can be imparted by disposing a non-woven fabric layer made of thicker fibers in the lower layer of the surface layer. Further, by combining the woven fabric, the strength can be improved and the form stability can be improved. Further, by using a hydrophilic polymer as the surface layer and a hydrophobic polymer as the lower layer, it is possible to improve the efficiency of polishing and cleaning by selectively retaining moisture in the surface layer in contact with the substrate.

  There is no limitation in particular as a method of laminating | stacking the said several fiber structure, The method illustrated below is employable. For example, it is possible to employ a method in which a fiber structure is integrated by fiber entanglement with a needle punch or high-pressure fluid flow in a state where a plurality of fiber structures are laminated. Since this method does not require the use of a binder, it is preferable because the air permeability, liquid permeability, and flexibility of the fiber structure are not impaired. When such a method is adopted, it is desirable that the fibers constituting the fiber structure can move freely to some extent. Therefore, the fiber structure is a short fiber knitted fabric, a short fiber nonwoven fabric, or a long fiber weave using a composite yarn having a different yarn length. It can be particularly preferably employed in the case of a long-fiber nonwoven fabric partially cut by a knitted fabric, a needle punch or the like. Among the fiber structures obtained by laminating by the above method, the fiber structure obtained by intertwining the fiber structures with a high-pressure fluid flow and being integrated is excellent in flexibility, and at the same time, the underlying fibers are on the surface. Since it is hardly exposed, it is one of the preferred embodiments. Moreover, fiber structures can also be integrated through an adhesive. Such an adhesive is not particularly limited, and general acrylic, polyurethane, polyamide, polyester, and vinyl adhesives can be used. In addition, in applying the adhesive, a method of applying the adhesive with a gravure roll, a method of applying with a spray, a method of laminating sheets containing the adhesive, etc. are adopted, and pressure and heat are appropriately applied. Can be integrated.

  Further, as another method for obtaining the fiber structure of the present invention, a papermaking method can be employed.

  The papermaking method will be described below.

  First, the first constituent fiber is cut into an appropriate fiber length with a guillotine cutter or a slicing machine. The fiber length of the short fibers thus obtained is preferably 0.1 to 20 mm, more preferably 0.1 to 5 mm, and more preferably 0.2 to 1 mm from the viewpoint of papermaking properties. More preferably. In this case, the above-described sea-island fiber or ultrafine fiber produced from the sea-island fiber can also be used. When sea-island type fibers are used, sea components are extracted in the process of forming the fiber structure or at the end.

  Next, the short fibers are beaten with a beater as necessary. By beating, the individual short fibers can be separated. Examples of the beater include Niagara beaters and refiners at the production level, and experimentally include a home mixer and cutter, a laboratory grinder, a biomixer, a roll mill, a mortar, and a PFI beater.

  The beating is preferably performed separately for the primary beating and the secondary beating. When the primary beating is performed with a Niagara beater or refiner, the short fibers are generally dispersed in water. However, it is preferable that the concentration of the fibers with respect to the entire dispersion is 5 wt% or less because the beating is performed uniformly. Moreover, since 0.1-1 wt% improves the efficiency of beating, it is more preferable.

  The secondary beating referred to in the present invention is beating the nanofibers subjected to the primary beating more precisely. Niagara beaters, refiners, PFI beating machines, etc. can be used as the apparatus used at this time, but the set clearance of each beating machine is preferably 0.1 to 1.0 mm, preferably 0.1 to 0.5 mm. It is more preferable that the pressure is reduced and the beating is performed under soft conditions. When the refiner is used, the shape of the processing blade incorporated in the apparatus can be appropriately changed, but it is preferable to select a shape having a scissor effect or shearing effect rather than cutting the fiber.

  When performing secondary beating with Niagara beaters and refiners, household and laboratory mixers, cutters, etc., the effect of cutting and crushing the fibers is great, and it is easy to cut or powder in the fiber length direction. It is preferable to beat with mild beating conditions such as rotation speed and pressurizing condition.

  Next, the adjustment method of the short fiber dispersion which is a raw material at the time of papermaking is demonstrated.

  The beaten short fibers and water, and if necessary, a dispersing agent and other additives are put into a stirrer and dispersed to a predetermined concentration. From the viewpoint of making the dispersibility of the short fibers in the dispersion uniform, the concentration of the short fibers in the dispersion is preferably 0.01 to 5.0 wt%. Furthermore, it is preferable to add a dispersant to the dispersion. The anionic, cationic, and nonionic dispersants are appropriately selected depending on the type and characteristics of the polymer constituting the short fiber. Even if the dispersant has the same structure, its molecular weight and the influence of other compounding agents You can use it properly according to the intended use. As a density | concentration of the dispersing agent to add, it is preferable that it is 0.01-1.0 wt%, and it is more preferable that it is 0.05-0.5 wt%. When the short fibers are sufficiently thin and the cohesive strength between the short fibers is high, paper can be made using only the fibers, and a fibrous binder can be used as necessary. When fibers are used as the binder, natural pulp (wood pulp, hemp pulp, straw, honey, etc.), easily fusible fibers having a low melting point component and a low softening point component are preferred, such as PE fiber, polypropylene (PP) fiber, PLA Fibers, polystyrene (PS) fibers, copolymerized polyamides and copolymerized polyester fibers, and core-sheath composite fibers having an easily fusible component as a sheath component are preferred.

  Using this dispersion, paper is made with a normal mechanical paper machine. As the paper machine, it is possible to use any of the long-mesh type paper machine, twin-wire type paper machine, and round net type paper machine, and an appropriate paper machine may be used according to the purpose and purpose. When making paper with a relatively large basis weight, it is preferable to use a long net paper machine.

  The papermaking obtained in this way may be used as a fiber structure as it is, but other fiber structures, plates, films, etc. can be combined and integrated. As the integration means, once the fiber structure is formed by the papermaking method, it may be integrated with another structure, or the paper structure is directly made on the other structure to produce the fiber structure of the present invention. It is also possible to obtain.

Further, the fiber structure of the present invention can also be obtained by the electrospinning method disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-123360. The fiber structure obtained by the electrospinning method does not have sufficient strength as it is, and is preferably combined and integrated with other fiber structures, plate-like bodies, films and the like. As an integration means, once the fiber structure is formed by the electrospinning method, the fiber structure may be integrated with another structure, or by directly performing electrospinning on another structure, the present invention. It is also possible to obtain a fiber structure of the present invention. It is one of the preferred embodiments of the present invention to form a recess in the surface of the fiber structure of the present invention thus obtained. Since the fiber structure of the present invention has a high ability to retain particles on the surface, when used as an abrasive cloth, agglomerated abrasive grains and polishing debris remain without being discharged from the surface of the fiber structure, resulting in defects such as scratches. May occur. By forming a concave portion on the surface of the fiber structure, such aggregated abrasive grains and polishing debris are taken into the concave portion, whereby generation of defects such as scratches can be suppressed.

  The shape and size of the recess must be appropriately selected according to the type of abrasive grains, the amount of slurry supplied, the moving speed of the polishing cloth, and the like.

  For example, the shape of the recess may be a circle, a polygon, or an indeterminate shape, or may be a straight, curved, or circumferential groove-like recess. Moreover, a part or all of each recessed part may be connected, and may exist in the completely independent state. Furthermore, the concave portion may be connected to the end of the fiber structure for supplying slurry or discharging polishing scraps, and a shape in which the groove-shaped concave portions intersect can also be adopted. The proportion of the recesses on the surface can also be selected as appropriate. However, if the amount is too small, the effect of the present invention cannot be obtained. On the other hand, if the amount is too large, the polishing efficiency is lowered. In general, the proportion of the recesses in the entire surface area is preferably 20 to 80%, more preferably 30 to 60%. In addition, if the depth of the concave portion is too shallow, aggregated abrasive grains and polishing scraps cannot be taken in. Therefore, the depth is preferably 1 μm or more, more preferably 10 μm or more, and further preferably 100 μm or more.

  As a method for forming such a recess, a method such as embossing, high-pressure fluid flow jetting, or chemical etching can be employed.

  Hereinafter, a method for forming the concave portion of the present invention by embossing will be described.

  Embossing refers to providing a concavo-convex pattern on a fibrous structure through a fibrous structure between a metal roll engraved with a concavo-convex pattern and a roll of elastic compressed cotton, compressed paper or rubber. In the present invention, since the purpose is to form a concave portion on the surface of the fiber structure, the shape of the engraving roll is preferably a roll having a convex portion on the mirror surface. Here, the convex portion of the engraving roll corresponds to the concave portion of the embossed fiber structure. The planar shape of the convex portion is preferably a square, rectangle, circle, ellipse, etc., and the cross-sectional shape in the thickness direction is also a square, rectangle, trapezoid or a spherical shape at the top, an ellipse, a semicircle, etc. Is preferred. Moreover, it is also possible to form a groove-shaped recessed part by using the engraving roll which has a linear convex part continuous in the width direction or the circumferential direction of the engraving roll. Further, for the purpose of obtaining the same effect as embossing, a flat plate having irregularities, a roll having a needle-like protrusion, or a flat plate can be used instead of the engraving roll.

  The optimum condition of the engraving roll temperature may be selected according to the processing speed, the thickness of the fiber structure, and the number of treatments. If the preferable range of conditions in embossing is exemplified, the processing temperature is preferably from a temperature lower by 10 ° C. than the melting point of the polymer constituting the constituent fiber to the vicinity of the softening point of the polymer. If the temperature of the roll is too high, the fibers are strongly fused, the surface of the fiber structure becomes hard, and defects such as scratches are liable to occur when used as an abrasive cloth or wiping cloth. In addition, when the roll temperature is too low, the embossing effect is low and a concave portion having a desired shape cannot be formed. Therefore, it is necessary to heat the roll as necessary, but the fiber diameter is very small. In this case, the roll temperature may be room temperature, that is, it may not be heated because the effect of the present invention can be achieved only by increasing the pressure between the rolls.

  Further, the pressure (linear pressure) between the rolls in embossing is generally preferably 5 to 400 kg / cm. If the pressure between the rolls is too high, the surface of the fiber structure is hard, which is not preferable because it tends to cause defects such as scratches when used as an abrasive cloth or a wiping cloth. Conversely, if the pressure is too low, Since the embossing effect is low and a recess having a desired shape cannot be formed, it is necessary to select appropriately according to the roll temperature, the processing speed, and the characteristics of the fiber structure. In general, the processing speed is 0.1 to 10 m / min, and the processing frequency is 1 to 10 times.

  For the purpose of smoothing the surface of the fiber structure, it is possible to use a combination of such embossing and pressing using a non-engraved mirror roll.

  Moreover, a recessed part can also be formed by injecting a high-pressure fluid flow on the surface of a fiber structure. In such a method, a recess having a desired shape can be formed depending on the shape, pattern, and movement of the nozzle for injecting the high-pressure fluid flow.

  Since the fiber structure of the present invention consists essentially of fibers, there is no binder on the surface for maintaining the shape of the recesses formed by these treatments. However, when the fiber structure of the present invention is used as a cleaning cloth or a polishing cloth in the presence of water, it is important that the concave portion maintain its form even in water. In response to such a requirement, for example, by setting the number average fiber diameter of the fibers forming the surface layer to 1 μm or less, preferably 500 nm or less, more preferably 300 nm or less, the cohesive strength of the fibers themselves is increased, and the shape retention of the recesses is increased. Since it can raise, it is preferable. Moreover, when forming a recessed part in the fiber structure surface or after forming a recessed part, it is also preferable to perform heat processing from the point which improves the form retainability of a recessed part. The temperature of such heat treatment is 100 ° C. or higher, preferably 120 ° C. or higher, and more preferably 130 ° C. or higher. In addition, when the polymer constituting the fiber melts, the flexibility that is characteristic of ultrafine fibers is impaired, and scratches occur when used as an abrasive cloth or wiping cloth. Is preferably processed at a temperature lower by 10 ° C. or more.

  The heat treatment method is not particularly limited, and can be appropriately selected from the methods exemplified below according to the purpose. For example, a method of exposing to high-temperature air, a method of irradiating infrared rays, a method of exposing to high-temperature water vapor, a method of immersing in hot water, and the like can be employed. In addition, examples of the apparatus at that time include a continuous dryer for transferring an object to be processed by a conveyor, a batch dryer such as a tumbler, a steamer, and a liquid dyeing machine.

  In the present invention, a polymer elastic body such as urethane may be provided within a range not impairing the effect of the obtained fiber structure. As such a polymer elastic body, various materials having desired texture, physical properties and quality can be appropriately selected and used, and examples thereof include polyurethane, acrylic, styrene-butadiene and the like. Among these, it is preferable to use polyurethane from the viewpoint of flexibility. The method for producing polyurethane is not particularly limited, and can be produced by appropriately reacting a conventionally known method, that is, polymer polyol, diisocyanate, and chain extender. Moreover, although it may be a solvent system or an aqueous dispersion system, the aqueous dispersion system is preferable from the viewpoint of the working environment.

  When impregnating the polymer elastic body, sufficient care must be taken so that the polymer elastic body is not substantially exposed on the surface. From that viewpoint, the amount of the elastic polymer is preferably 10% or less, more preferably 5% or less, and still more preferably 2% or less of the total weight. In addition, when using a solvent-based polymer elastic body, a wet coagulation method is adopted. When using a water-dispersed polymer elastic body, a heat-sensitive coagulation material is used. It is preferable to suppress.

Furthermore, a through-hole can be formed in the fiber structure or laminated fiber structure of the present invention described so far. By forming such a hole, discharge of agglomerated abrasive grains and polishing scraps is promoted, and the flexibility of the fiber structure or laminated fiber structure is improved, which is preferable. The shape of the hole is not particularly limited, and may be appropriately selected from a circle, an ellipse, a triangle, a quadrangle, a polygon, an indeterminate shape, and the like as necessary. Also, if the size of the hole is too small, there will be no effect of discharging aggregated abrasive grains and polishing debris. Conversely, if the size is too large, the polishing rate may be reduced or polishing may be uneven. The area of the hole is preferably 1 μm ^{2 to 5} cm ² . Similarly, if the proportion of holes in the surface is too small, the effect of discharging aggregated abrasive grains and polishing debris will not be obtained. Conversely, if it is too large, the polishing rate may decrease or polishing may become uneven. Therefore, the proportion of holes in the surface is preferably 10 to 50% in terms of area ratio.

  Despite the fact that the fiber structure obtained by the present invention consists essentially of fibers, it is very dense, so that it has excellent surface flexibility and good fine particle retention properties. It has characteristics not found in the structure. Therefore, for example, when used for a wiping cloth such as a glasses wipe, there is a feature that not only the wiping property is excellent but also the object is not damaged. Furthermore, when used as a polishing cloth used in the manufacturing process of hard disks, silicon wafers, integrated circuit boards, precision equipment, optical parts, etc., scratches are generated because the abrasive grains are less likely to aggregate due to the high effect of gripping the abrasive grains. The polishing rate can be increased while preventing this.

  Hereinafter, the present invention will be specifically described based on examples. In addition, the measuring method in an Example used the following method.

A. Polymer melt viscosity The polymer melt viscosity was measured using a Capillograph 1B manufactured by Toyo Seiki Co., Ltd. The polymer storage time from sample introduction to measurement start was 10 minutes.

B. Melting | fusing point The peak top temperature which shows melting | dissolving of a polymer by 2nd run using DSC-7 made from Perkin Elmer Co., Ltd. was made into melting | fusing point of a polymer. The temperature rising rate at this time was 16 ° C./min, and the sample amount was 10 mg.

C. Fiber cross-sectional observation by TEM Ultra-thin sections were cut in the cross-sectional direction of the fiber, and the fiber cross-section was observed with a transmission electron microscope (TEM). Nylon was metal dyed with phosphotungstic acid.
TEM apparatus: H-7100FA type manufactured by Hitachi, Ltd. SEM Observation A platinum-palladium alloy was deposited on the fiber, and the fiber side surface was observed with a scanning electron microscope (SEM).
SEM apparatus: Hitachi S-4000 type Single fiber diameter by number average of fibers At least 300 single fibers are observed with a TEM or SEM in the above section D at a magnification that can be observed in one field of view. A simple average value of the diameters was determined. At this time, 300 diameters randomly extracted in the same visual field were analyzed and used for calculation.

F. Air permeability The measurement was performed based on the method (fragile method) defined in JIS L-1096.

G. Polishing characteristics The fiber structure (sheet) was slit into a tape having a width of 38 mm, and polishing was performed under the following conditions. That is, a free abrasive slurry comprising a diamond crystal having a primary particle diameter of 1 to 10 nm on the surface of a polishing cloth using a disk which is subjected to Ni-P plating treatment on an aluminum substrate, polished and controlled to an average surface roughness of 0.2 nm. Was dropped at a supply rate of 10 ml / min, and polishing was performed for 30 seconds under the conditions of a disc rotation speed of 300 rpm, a pressing pressure of the tape to the disc of 1.0 kg / cm ² , and a tape running speed of 6 cm / min.

  In accordance with JIS B0601 (2001 edition), using the TMS-2000 surface roughness measuring instrument manufactured by Schmitt Measurement Systems, Inc., any 10 locations on the disk substrate sample surface after texturing The surface roughness was measured and the substrate surface roughness was calculated by averaging the measured values at 10 locations. The lower the value, the higher the performance.

H. Polishing rate of silicon wafer The weight of the wafer on the cloth before and after polishing was measured, and the decrease was divided by the polishing time to obtain the polishing rate.

Example 1
Poly L with a melt viscosity of 212 Pa · s (262 ° C., shear rate 121.6 sec ⁻¹ ), a melting point of 220 ° C. N6 and a weight average molecular weight of 120,000, a melt viscosity of 30 Pa · s (240 ° C., 2432 sec ⁻¹ ), and a melting point of 170 ° C. Using lactic acid (optical purity 99.5% or more), the content of nylon 6 (N6) was 45% by weight, the kneading temperature was 220 ° C., and melt kneading to obtain a polymer alloy chip. The weight average molecular weight of polylactic acid was determined as follows. The sample chloroform solution was mixed with THF (tetrahydrofuran) to obtain a measurement solution. This was measured at 25 ° C. using water permeation gel permeation chromatography (GPC) Waters 2690, and the weight average molecular weight was determined in terms of polystyrene. Moreover, the melt viscosity of this poly L lactic acid at 215 ° C. and 1216 sec ⁻¹ was 86 Pa · s.

The polymer alloy chip thus obtained was spun from the pores at a spinning temperature of 240 ° C., then spun at a spinning speed of 4500 m / min by an ejector, collected on a moving net conveyor, and a crimping rate of 16%. With an embossing roll, thermocompression bonding was performed under the conditions of a temperature of 80 ° C. and a linear pressure of 20 kg / cm to obtain a long fiber nonwoven fabric having a single fiber fineness of 2.0 dtex and a basis weight of 150 g / m ² .

An oil agent (SM7060: manufactured by Toray Dow Corning Silicone Co., Ltd.) is applied to the nonwoven fabric made of this polymer alloy fiber by 2% by weight with respect to the fiber weight, and a needle punch is applied at a punch number of 1000 / cm ^2. A nonwoven fabric made of polymer alloy fibers having a density of 120 g / m ² and a density of 0.09 g / cm ³ was obtained. The nonwoven fabric is laminated with a needle punched nonwoven fabric made of polyester short fibers with a single fiber fineness of 0.1 dtex, and a water flow with a pressure of 12 MPa is injected from a nozzle having 0.1 mmφ holes opened at intervals of 0.6 mm for integration. A composite sheet was obtained. The processing speed was 1 m / min, and the nozzle was processed while swinging at 18.6 Hz with an amplitude of 4 mm in the width direction. The cover factor in this case was 150%. This fiber structure was immersed in a 3% aqueous sodium hydroxide solution (95 ° C., bath ratio 1: 100) for 2 hours to hydrolyze and remove 99% or more of the sea polymer in the polymer alloy fiber. When the composite sheet in this state was observed with an SEM, a fiber bundle in which 500 or more ultrafine fibers were aggregated was formed. The fiber was drawn from the composite sheet, and the fiber cross section was observed with a TEM to determine the single fiber diameter (number average fiber diameter) of the fiber, which was 110 nm. Moreover, the thickness of this fiber structure was 0.5 mm. The air permeability of this fiber structure was 0.5 cc / cm ² / sec.

  Furthermore, the obtained composite sheet was slit into a tape having a width of 38 mm, and polishing characteristics were evaluated.

  The surface roughness of the disc after polishing was 0.30 nm, which was very smooth. Further, a polishing rate as high as 4.5 mg / min was obtained. In FIG. 1, the SEM photograph of the fiber structure surface created in Example 1 is shown.

Example 2
The composite sheet obtained in Example 1 was sprayed with a water flow having a pressure of 1 MPa from a nozzle having 0.1 mmφ holes at intervals of 0.6 mm. The processing speed was 1 m / min, and the nozzle was processed while swinging at 18.6 Hz with an amplitude of 4 mm in the width direction.

The composite sheet thus obtained was slit into a tape having a width of 38 mm, and polishing characteristics were evaluated. Moreover, the thickness of this composite sheet was 0.6 mm. The fiber structure had an air permeability of 0 cc / cm ² / sec (below the measurement limit).

  When the disc was polished under the same conditions as in Example 1, the surface roughness of the disc after the polishing was 0.26 nm, which was very excellent in smoothness. A polishing rate as high as 4.8 mg / min was obtained. In FIG. 2, the SEM photograph of the fiber structure surface created in Example 2 is shown.

Example 3
The fiber structure obtained in Example 1 was embossed to form random streak-like recesses. The processing speed was 1.5 m / min, and the engraving roll temperature was 140 ° C. On the surface after embossing, a streak-like depression having a depth of several μm surrounding a region of about 500 μm was formed. When the disc was polished under the same conditions as in Example 1, the surface roughness of the disc after polishing was as excellent as 0.24 nm and excellent in smoothness. A polishing rate as high as 4.6 mg / min was obtained.

Comparative Example 1
In producing the long fiber nonwoven fabric in Example 1, a long fiber nonwoven fabric was produced in the same manner as in Example 1 except that poly-L lactic acid was used instead of the polymer alloy chip. Further, the long fiber nonwoven fabric was integrated with a polyester single fiber needle punch nonwoven fabric in the same manner as in Example 1. Thereafter, immersion in an aqueous sodium hydroxide solution was not performed.

When the surface of the obtained fiber structure was observed by SEM and the fiber diameter of the fiber existing on the surface was measured, it was 4.5 μm. Moreover, the thickness of this fiber structure was 0.7 mm. The air permeability of this fiber structure was 24 cc / cm ² / sec. When the disc was polished under the same conditions as in Example 1, the surface roughness of the disc after polishing was inferior in smoothness to 0.42 nm. Further, only a polishing rate as low as 3.0 mg / min was obtained.

Example 4
The polymer alloy chip produced in Example 1 was melt-spun to obtain a highly oriented undrawn yarn of 92 dtex 36 filaments, and further subjected to drawing heat treatment to obtain a polymer alloy fiber of 67 dtex, 36 filaments. In this polymer alloy fiber, N6 was uniformly dispersed with a number average diameter of 110 nm. A 67 dtex, 36 filament polymer alloy fiber was cut to 2 mm with a guillotine cutter, then treated with 98 ° C., 10% sodium hydroxide for 1 hour to remove poly-L-lactic acid and filtered through a filter. Sodium oxide was removed to obtain ultrafine short fibers. About 20 liters of water and 30 g of this short fiber were put into a Niagara beater, and the fiber was first beaten for 10 minutes. This primary beaten fiber was secondarily beaten for 10 minutes with a PFI beater to obtain a secondary beaten fiber. Water containing this secondary beating fiber and an anionic dispersant was dispersed with a mixer to obtain a dispersion. The obtained dispersion was put into a container of a laboratory paper machine, and paper was made on artificial leather made of polyester microfiber and polyurethane previously placed on a paper net for papermaking. The fiber structure thus obtained was subjected to a heat treatment at 140 ° C. for 5 minutes with a box dryer to obtain a laminated fiber structure having a fiber structure consisting of only fibers in the surface layer. The thickness of this composite sheet was 0.9 mm. The fiber structure had an air permeability of 0 cc / cm ² / sec (below the measurement limit). In addition, the fiber structure was sliced in the thickness direction so that the thickness on the side including the surface layer was 0.3 mm using a slicing machine having a mechanism in which an endless belt-shaped knife traveled and sliced the sample. The air permeability of the sample including the surface layer was 0 cc / cm ² / sec (below the measurement limit). When the disc was polished under the same conditions as in Example 1, the surface roughness of the disc after polishing was 0.20 nm, which was very excellent in smoothness. A polishing rate as high as 4.9 mg / min was obtained.

Example 5
A plain woven fabric was prepared using the polymer alloy filament obtained in Example 4 and immersed in a 3% aqueous sodium hydroxide solution (95 ° C., bath ratio 1: 100) for 2 hours to obtain a sea polymer in the polymer alloy fiber. 99% or more was removed by hydrolysis. The number average fiber diameter of the fibers of the obtained woven fabric was 120 nm. The air permeability of this woven fabric was 0 cc / cm ² / sec (below the measurement limit). This woven fabric was affixed with a double-sided tape on a pad (Suba800 manufactured by Nitta Haas) impregnated with a polymer elastic body into the nonwoven fabric to prepare a polishing pad. Using this polishing pad, a 4 inch silicon wafer after etching was polished using a slurry containing colloidal silica (Granzox 3900 manufactured by Fujimi Incorporated was diluted 10 times). At this time, polishing was performed with a platen rotation number of 60 rpm, a slurry supply amount of 20 cc / min, and a pressure of 13720 Pa. At this time, the polishing rate was 3 mg / min.

Comparative Example 3
The etched 4-inch silicon wafer was polished under the same conditions as in Example 5 using a pad (Nita Haas Company Suba800) to which no fabric was applied. At this time, the polishing rate was 2 mg / min.

  The fiber structure of the present invention is suitably used for polishing cloths and cleaning tapes used in the manufacturing process of, for example, wiping cloths such as wiping glasses, hard disks, silicon wafers, integrated circuit boards, precision instruments, optical components, etc. Can do.

2 is a SEM photograph showing the shape of the fiber on the surface of the fiber structure of the present invention created in Example 1. It is a SEM photograph which shows the shape of the fiber of the fiber structure surface of this invention created in Example 2. FIG.

Claims (7)

A fiber structure substantially comprising only fibers, wherein the air permeability is ² cc / cm ² / sec or less.   The number average fiber diameter of the fiber which comprises a fiber structure is 1 micrometer or less, The fiber structure of Claim 1 characterized by the above-mentioned.   The fiber structure according to claim 1, wherein a concave portion is formed on the surface. The fiber structure according to claim 1, wherein the air permeability of the surface layer is ² cc / cm ² / sec or less.   The through hole is formed, The fiber structure in any one of Claims 1-4 characterized by the above-mentioned.   A laminate comprising the fiber structure according to any one of claims 1 to 5 and at least one selected from the group consisting of another fiber structure, a plate-like body and a film. Fiber structure. The laminated fiber structure according to claim 6, wherein a through-hole is formed.