JP5387217B2 - Polishing cloth - Google Patents

Description

  The present invention relates to an abrasive cloth made of polyamide 56 fibers.

  Polyamide 6 fibers have been mainly used for polishing cloths used for processing the substrate surface of precision instruments. Polyamide 6 fiber is excellent in wear resistance, hardly hydrolyzed, and excellent in flexibility. In addition, since polyamide 6 constituting polyamide 6 fiber has an amide bond in the polymer, it has higher water absorption than fibers such as polyester that do not have an amide bond. The liquid has a high affinity with the liquid and a good slurry retention.

  However, in recent high-precision polishing, further improvement in the ability of the polishing cloth to carry the slurry quickly and uniformly is required. For this purpose, it is necessary to improve the water absorption and water retention of the polyamide 6 fiber. there were.

  Conventionally, a method of hydrophilizing a polishing cloth has been proposed (see Patent Documents 1 and 2). However, if there is a hydrophilic processing spot, it becomes a slurry-supporting spot or the abrasive dispersibility in the slurry is deteriorated, so that it has not fully satisfied the recent demand for high precision polishing.

  By the way, in addition to polyamide 6 and polyamide 66, polyamide 56 includes polyamide 56. The fiber made of polyamide 56 is said to be suitable for fishing lines and the like because of its excellent transparency and high strength (see Patent Document 3). However, when this polyamide 56 fiber is used for polishing purposes, it is polished. Scratches at the time of polishing due to fiber fluff inside and fibers falling off occurred, and the required characteristics were not satisfied in terms of high precision polishing.

JP 2000-237951 A JP 2002-224945 A JP 2006-144163 A

  Therefore, an object of the present invention is to provide a polishing cloth made of polyamide 56 fiber that is excellent in water absorption and can suppress scratches during polishing and the like, and is particularly suitable for high-precision polishing.

  That is, in the polishing cloth of the present invention, 90 mol% or more of the repeating units are composed of pentamethylene adipamide units, the sulfuric acid relative viscosity is 3 to 8, and the molecular weight dispersity (Mw / Mn) is 1.5 to 3. A polishing cloth comprising a sheet-like material comprising a polyamide 56 fiber having a tensile strength of 4 to 11 cN / dtex.

  According to a preferred aspect of the polishing cloth of the present invention, the single fiber diameter based on the number average of the polyamide 56 fibers is 0.1 to 10 μm.

  According to a preferred aspect of the polishing cloth of the present invention, the sheet-like material is made of a nonwoven fabric and contains an elastic polymer.

  According to the preferable aspect of the polishing cloth of the present invention, the stress at the time of 10% elongation of the warp or the width of the sheet-like material is 5 N / cm or more.

  According to the present invention, it is excellent in water absorption and polishing slurry retention, can suppress fiber breakage and fiber dropping during polishing, and can be used for high-precision polishing that can suppress scratches and polishing marks. A cloth is obtained.

  It is important that the polishing cloth of the present invention comprises a sheet-like material having polyamide 56 fibers. By using the polyamide 56 fiber, it becomes possible to carry the slurry quickly and uniformly, and an excellent performance as a polishing cloth for high-precision polishing can be exhibited. The reason for this is considered that the polyamide 56 constituting the polyamide 56 fiber has a larger number of amide bonds per unit mass of the polymer than the polyamide 6 and the polyamide 66, and has high hydrophilicity.

  Therefore, it is important that the polyamide 56 in the polishing cloth of the present invention comprises 90 mol% or more of repeating units composed of pentamethylene adipamide units. It is possible to exhibit excellent water absorption by making pentamethylene adipamide units 90% by mole or more, preferably 95% by mole or more, more preferably 97% by mole or more of the repeating units, and the regularity of the molecular chain. Increases, and orientational crystallization easily occurs, so that a fiber having excellent mechanical properties can be obtained. The pentamethylene adipamide unit of polyamide 56 is composed of 1,5-pentamethylenediamine and adipic acid.

  The abrasive cloth of the present invention may contain other copolymerization component of less than 10 mol% within a range not impairing the effects of the present invention, but in order to easily exhibit the excellent water absorption targeted by the present invention. As described above, the pentamethylene adipamide unit is more preferably 95 mol% or more, and still more preferably 97 mol% or more.

  Examples of copolymer components that may be contained in the polyamide 56 in less than 10 mol% include oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid. Aliphatic carboxylic acids, cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and 5-sodium sulfoisophthalic acid Mention may be made of structural units derived from acids.

  Further, the polymer constituting the polyamide 56 fiber (polyamide 56) may contain additives such as particles, flame retardants and antistatic agents, as long as the object of the present invention is not impaired.

  It is important that the polyamide 56 forming the polyamide 56 fibers has a sulfuric acid relative viscosity of 3 to 8. Sulfuric acid relative viscosity is an index of molecular weight, and sulfuric acid relative viscosity should be 3 or more, preferably 3.1 or more, more preferably 3.2 or more, still more preferably 3.3 or more, and further preferably 3.4 or more. Thereby, fiber strength improves. This is because, due to the high molecular weight, the number of molecular chain ends that tend to cause structural defects in the fiber is reduced per unit volume, and because the molecular chain length is long, one molecular chain is physically entangled with more molecular chains. It is considered that the interaction such as hydrogen bond and van der Waals force is caused, and the spinning stress and the drawing stress are transmitted uniformly, and the molecular chain is uniformly oriented in the fiber manufacturing process. On the other hand, by setting the relative viscosity of sulfuric acid to 8 or less, preferably 7 or less, more preferably 6 or less, further preferably 5 or less, more preferably 4 or less, melt spinning at an appropriate spinning temperature becomes possible, and the inside of the spinning machine Therefore, the thermal decomposition of the polymer at 1 is suppressed, so that the yarn-making property is improved and the coloring of the fiber is also suppressed. Moreover, by suppressing thermal decomposition, the dispersity (Mw / Mn) described later can also be reduced.

  It is important that the polyamide 56 forming the polyamide 56 fiber has a molecular weight dispersity (Mw / Mn) of 1.5 to 3. Here, Mw is a weight average molecular weight, Mn is a number average molecular weight, and the smaller the Mw / Mn that is the ratio of both, the narrower the molecular weight distribution is. By setting Mw / Mn to 3 or less, preferably 2.8 or less, more preferably 2.6 or less, and even more preferably 2.4 or less, high-strength fibers combined with high sulfuric acid relative viscosity as described above can do. This is because Mw / Mn is small, that is, the distribution of molecular chain length is small, and the number of molecular chains that interact with each other, physical entanglement force, hydrogen bonding force and van der Waals force. As the interaction forces such as are almost uniform, each molecular chain is equally spun and stretched in the spinning process. As a result, the amorphous phase molecular chains are evenly oriented and highly densely oriented. It is presumed that many crystal phases are formed.

  Furthermore, due to the effect of uniform orientation of the molecular chains, there are many amorphous chains that connect the crystalline phases in the amorphous phase, and the molecular chain lengths of the amorphous chains are relatively equal. It is presumed to exist in an equivalent tension state (state in which movement is constrained by the crystal phase). That is, it contains many densely oriented crystal phases, and the crystal phases are connected by many tensioned amorphous chains, and thus it is estimated that these act synergistically and become high-strength polyamide 56 fibers. doing. Although Mw / Mn is preferably as small as possible, the level that can be produced is 1.5 or more.

  Moreover, it is important that the polyamide 56 fiber used in the present invention has a tensile strength of 4 to 11 cN / dtex. When the tensile strength is 4 cN / dtex or more, sufficient polishing cloth strength can be obtained, fiber breakage at the time of polishing hardly occurs, pressure spots at the time of polishing due to the fallen portion of the broken fiber, and abrasive dispersion in the slurry Scratch generation due to deterioration of the state can be suppressed.

  The higher the tensile strength, the better. However, it is more preferably 10 or less, and even more preferably 9 or less, so that the tension can be evenly distributed when partial tension spots during polishing, particularly high tension portions, are generated. 8.5 or less is the most preferred embodiment.

  The polyamide 56 fiber of the present invention is such a high-strength fiber. However, in the prior art, if an attempt is made to produce a polyamide 56 filament fiber having a small total fineness and single fiber fineness, fluff and yarn breakage occur in the drawing process. Since it was easy to do, it had to reduce a draw ratio and it was difficult to manufacture a high intensity | strength fiber.

  Therefore, as a result of intensive studies by the present inventors, 1,5-pentamethylenediamine, which is a raw material of polyamide 56, is easy to volatilize and cyclize in the polymerization process, and polyamide 56 is not a polymer having a high melt storage stability. In addition, since the crystallinity is lower than that of the conventional polyamide 66, the molecular weight distribution is easy to spread in the polymerization process and the spinning process, and particularly in the high molecular weight polyamide 56, Mw / Mn exceeds 3. It has been found that it becomes difficult to orient molecular chains uniformly in the spinning process and the drawing process, which induces fluff and yarn breakage. Therefore, by adopting a specific manufacturing method as described later, filament fibers made of polyamide 56 having a narrow molecular weight distribution can be formed for the first time while having a high molecular weight. They succeeded in obtaining polyamide 56 fibers.

  Surprisingly, it has been found that polyamide 56 fibers having Mw / Mn of 3 or less can be stronger than conventional polyamide 66. This is presumed to be due to the low crystallinity of the polyamide 56, which makes it difficult for spherulites to be formed in the spinning process, resulting in fibers containing no structural defects.

  The average fiber diameter of the polyamide 56 fibers used in the polishing cloth of the present invention is preferably 0.1 to 10 μm. By setting the average fiber diameter to 0.1 μm or more, the strength of the fiber can be maintained, cutting due to a decrease in strength can be suppressed, and fiber aggregation due to an increase in surface area can be made difficult to occur. By setting the average fiber diameter to 10 μm or less, the density of the polishing cloth surface fibers can be increased, and the surface roughness of the polishing cloth can be reduced. The average fiber diameter is more preferably 0.3 to 5 μm, still more preferably 0.5 to 3 μm.

  As the sheet-like material used as the polishing cloth of the present invention, a woven or knitted fabric or a non-woven fabric can be used as a base material. Among these, from the viewpoint of surface uniformity and sheet strength, woven fabrics and fibers are intertwined. A nonwoven fabric is preferably used. As the woven fabric, plain woven fabric, twill woven fabric, satin woven fabric, and woven fabrics having these changed structures can be adopted. As the nonwoven fabric, short fiber nonwoven fabric obtained by forming a laminated web using a card or a cross wrapper and then performing needle punching or water jet punching, a nonwoven fabric obtained from a spunbond method or a melt blow method, and the like Nonwoven fabrics obtained by a papermaking method can be employed. Among these, short fiber nonwoven fabrics and spunbond nonwoven fabrics are preferably used because the fiber length is as long as 1 cm or more and a sheet-like material having good strength can be obtained.

  Moreover, it is a preferable form to make the above-mentioned nonwoven fabric contain an elastic polymer in accordance with required characteristics such as the surface form of the sheet-like material, the high elongation and the cushioning property. Due to the binder effect of the elastic polymer, it is possible to prevent the polyamide 56 fibers from falling off the sheet-like material.

  In the present invention, polyurethane, polyurea, polyurethane / polyurea elastomer, polyacrylic acid, acrylonitrile / butadiene elastomer, styrene / butadiene elastomer, etc. can be used as the elastic polymer, but polyurethane is preferred from the viewpoint of flexibility and cushioning properties. Used.

  Examples of the polyurethane include at least one polymer diol selected from polyester diols having an average molecular weight of 500 to 3000, polyether diol, polycarbonate diol, polyester polyether diol, and the like, and 4,4′-diphenylmethane. At least one diisocyanate selected from aromatic diisocyanates such as diisocyanates, alicyclic diisocyanates such as isophorone diisocyanate, and aliphatic diisocyanates such as hexamethylene diisocyanate, ethylene glycol, butanediol, ethylenediamine and 4,4 ′ -Polyurethane obtained by reacting at least one low molecular weight compound having two or more active hydrogen atoms such as diaminodiphenylmethane at a predetermined molar ratio and its Sex products thereof.

  The elastic polymer may contain polyester resins, polyamide resins, polyolefin resins and the like, acrylic resins, ethylene-vinyl acetate resins, and the like.

  In addition, the elastic polymer used in the present invention may include pigments such as carbon black, dye antioxidants, antioxidants, light-proofing agents, antistatic agents, dispersants, softeners, coagulation modifiers, difficulty if necessary. Additives such as a flame retardant, an antibacterial agent and a deodorant may be blended.

  It is preferable that the content rate of an elastic polymer is 0-100 mass% with respect to base materials, such as a nonwoven fabric. Depending on the content of the elastic polymer, the surface state, cushioning properties, hardness, strength, and the like of the polishing cloth can be adjusted. When the content of the elastic polymer is 5% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more, fiber dropping can be reduced. On the other hand, by setting the content of the elastic polymer to 100% by mass or less, more preferably 80% by mass or less, and still more preferably 60% by mass or less, it is possible to obtain a state in which the polyamide 56 fibers are uniformly dispersed on the sheet surface. it can.

  The polishing cloth of the present invention preferably has a vertical or horizontal stress at 10% elongation of 5 N / cm or more. When the 10% elongation stress of the polishing cloth is 5 N / cm width or more, the shape stability is excellent during polishing. In the case of tape polishing, the elongation of the polishing cloth is small, the fineness of the surface fibers can be maintained, and ultra high accuracy. The surface roughness can be achieved. In addition, there are few voids on the surface of the polishing cloth that are expressed by elongation, and there are few voids due to agglomeration of abrasive grains. More preferably, the stress at 10% elongation is 10 N / cm or more, and further preferably 20 N / cm or more. Further, if the stress at 10% elongation is too high, the polishing cloth becomes difficult to absorb tension at the time of momentary tension increase during polishing, and therefore the stress at 10% elongation is preferably 200 N / cm or less.

  As a means for improving the stress at 10% elongation and the strength of the sheet-like material used in the present invention, for example, the following method can be employed. That is, when the sheet-like material used as the polishing cloth is a woven or knitted fabric, it is preferable to select yarns that do not easily stretch as warps and wefts, and woven fabrics using uncrimped yarns are particularly suitable. In addition, when the sheet-like material used as the polishing cloth is a non-woven fabric, it is adjusted by fiber orientation or entanglement between fibers by needle punching treatment or water jet punching treatment, or the above-described high amount that becomes a binder between fibers. A molecular elastic body can also be provided. When the sheet-like material is a non-woven fabric, a woven fabric, a knitted fabric, or a film that serves as a reinforcing layer may be laminated on the sheet-like material. When a nonwoven fabric and a woven or knitted fabric are laminated and integrated as a sheet-like material by needle punching, it is preferable that the yarn of the woven or knitted fabric is a strong twisted yarn in order to prevent damage to the fibers constituting the woven or knitted fabric. The twist number of the yarn is preferably in the range of 500 T / m to 4500 T / m. Further, the fiber diameter of the woven or knitted fabric may be the same as or smaller than the fiber diameter of the ultrafine fiber nonwoven fabric.

  In addition, various methods such as a method of adhering the nonwoven fabric and the above-mentioned reinforcing layer with a binder, a method of laminating a reinforcing layer in which a heat fusion polymer is premixed and a nonwoven fabric, and heat-sealing with a heating roll can be adopted. it can.

  As a material used as a film here, any material having a film shape such as polyolefin, polyester or polyphenyl sulfide can be used. However, in view of versatility, it is desirable to use a polyester film. .

The basis weight of the polishing cloth of the present invention is preferably 100 to 500 g / m ² . By setting the basis weight to 100 g / m ² or more, more preferably 150 g / m ² or more, sufficient shape stability and dimensional stability for the polishing cloth can be obtained. On the other hand, when the basis weight is 500 g / m ² or less, more preferably 300 g / m ² or less, sufficient flexibility for the polishing cloth can be obtained.

  The thickness of the polishing cloth of the present invention is preferably 0.1 to 2 mm. By setting the thickness to 0.1 mm or more, preferably 0.3 mm or more, sufficient form stability and dimensional stability can be obtained. On the other hand, by setting the thickness to 2 mm or less, more preferably 1 mm or less, and even more preferably 0.7 mm or less, the roll diameter becomes compact when the roll is formed by winding the abrasive cloth, and the roll is sufficiently contained in one roll. A length of polishing cloth can be wound up.

  The polishing cloth of the present invention is preferably subjected to napping treatment on at least one side. By doing in this way, a precise touch is obtained and it is suitable as a polishing cloth for high-precision polishing.

  Next, an example of the preferable manufacturing method of the abrasive cloth of this invention is demonstrated.

  The abrasive cloth of the present invention can be obtained, for example, by combining the following steps. In other words, it is classified into a polyamide 56 resin production process for monomer synthesis and polymerization, a yarn production process in which the obtained polyamide 56 resin is made into a fibrous form, and a process in which the obtained polyamide 56 fiber is made into a sheet-like material, and is specified in each process. It is preferable to adopt this manufacturing method. Next, a preferable aspect is demonstrated in order from a polyamide 56 resin manufacturing process.

  In the monomer synthesis step as a raw material for the polyamide 56 resin, 1,5-pentamethylenediamine is preferably synthesized from a biomass-derived compound such as glucose or lysine by an enzyme reaction, a yeast reaction, a fermentation reaction, or the like. According to the above method, since the content of a compound such as 2,3,4,5-tetrahydropyridine and piperidine is small and high-purity 1,5-pentamethylenediamine can be prepared, the melt storage stability is high. It becomes a polyamide 56 resin, and the molecular weight is lowered in the melt spinning process, so that Mw / Mn is hardly increased. Of course, there is also an advantage that it is excellent in environmental adaptability. Specifically, Japanese Patent Application Laid-Open Nos. 2002-223971, 2004-000114, 2004-208646, 2004-290091, 2004-298034, 2002-223770. 1,5-pentamethylenediamine, or 1,5-pentanediamine / hydrochloride or 1,5-pentamethylenediamine / adipate disclosed in Japanese Patent Laid-Open No. 2004-222569 and the like. Polyamide 56 is preferable, and it is preferable to polymerize using 1,5-pentamethylenediamine adipate because it is easy to obtain a raw material with higher purity. Moreover, about adipic acid, another diamine component, and dicarboxylic acid component, what was manufactured by the conventionally well-known method can be used.

  Next, a method for polymerizing the polyamide 56 resin used in the polishing cloth of the present invention will be described. The polyamide 56 resin constituting the polyamide 56 fiber used in the present invention has a high relative viscosity of sulfuric acid of 3 or more. However, if such a high molecular weight polyamide 56 is produced only by the heat polymerization method, the polymerization reaction is delayed. Therefore, the inside of the polymerization can must be kept at a high temperature of 240 ° C. or higher for a long time, and the polymerization time tends to be longer than the conventional heat polymerization of polyamide 66. This is because 1,5-pentamethylenediamine, which is a raw material for polyamide 56 resin, has a low boiling point, and therefore volatilizes at high temperatures and easily flows out of the system. It is presumed that the molar balance between the diamine and the dicarboxylic acid in the polymerization can easily breaks due to the change to basic amines such as 1,5-tetrahydropyridine, piperidine and ammonia. And when Mw / Mn having a relative viscosity of 3 or more of sulfuric acid produced by only the heat polymerization method is 3 and the melt spinning is performed, the Mw / Mn of the polyamide 56 filament fiber spun becomes 3 or more. It has been found that it is difficult to produce a strength fiber, and it is particularly difficult to produce a fiber having a small single yarn fineness suitable for high-precision polishing. This is because a thermal delay occurs in the latter stage of polymerization due to polymerization delay, resulting in a polyamide 56 resin having an Mw / Mn of more than 3, or even if a resin having an Mw / Mn of 3 or less is obtained, This is because the molecular weight distribution becomes large due to thermal decomposition in the melt spinning process.

  Therefore, in order to produce a polyamide 56 fiber made of a polyamide 56 resin having a sulfuric acid relative viscosity of 3 or more and Mw / Mn of 3 or less as in the present invention, in the production of the polyamide 56 resin as a raw material, the sulfuric acid relative viscosity is It is preferable that a polyamide 56 resin having a 2.9 or less is previously produced by a heat polymerization method and pelletized, and then the degree of polymerization of the polyamide 56 resin is increased by a solid phase polymerization method. Furthermore, since the polyamide 56 is not a polymer having a very high heat resistance and a low crystallinity as compared with the conventional polyamide 66, it is preferable to precisely control the polymerization conditions in the solid phase polymerization. In particular, in order to allow the polymerization reaction to proceed uniformly in the solid phase polymerization, it is preferable to prepare a polyamide 56 resin having an amino terminal group and a carbo terminal group in a well-balanced manner in advance by a heat polymerization method, and subject this to solid phase polymerization.

  As described above, in the production of the polyamide 56 fiber of the present invention, it is important to strictly control the production conditions of the polyamide 56 resin as a precursor. Here, the preferred heat polymerization method and solid phase polymerization method are first described. explain.

  The heat polymerization method used in the present invention is a polymerization method for obtaining polyamide 56 resin by heating and dehydrating and condensing an aqueous solution containing diamine and adipic acid as raw materials. The raw material adjustment process to be put into the can, the polymerization system is heated while maintaining a slightly pressurized state, the concentration process in which the water in the aqueous solution is volatilized and the raw material is concentrated, and the inside of the polymerization system is made a closed system. A pressure increasing step for increasing the pressure to a desired pressure in the pressure suppressing step by heating the aqueous solution containing the water, and a pressure suppressing step for generating a prepolymer by heating while maintaining the inside of the polymerization system at a constant pressure. , Releasing the pressure to return to normal pressure, raising the temperature in the polymerization system to above the melting point of the prepolymer, and reducing the pressure to heat the product polymer to the melting point of the polymer and hold it under reduced pressure to advance the polycondensation And inactive Preferably includes a discharge step of pelletizing by ejecting the produced polymer by injecting the gas into the polymerization reactor.

As described above, 1,5-pentamethylenediamine, which is a raw material for polyamide 56 resin, has a lower boiling point than that of 1,6-hexamethylenediamine, which is a raw material for conventional polyamide 66 (the former: about 180 ° C., the latter : About 200 ° C.), and it tends to volatilize at the temperature of the heat polymerization, so that the molar balance of the amino terminal group and the carboxyl terminal group in the polymerization can collapses in the latter stage of the polymerization, which tends to cause polymerization delay. Therefore, if the polymerization time is prolonged, it tends to induce the formation of a basic amine by intramolecular deammonia reaction of 1,5-pentamethylenediamine. It is preferable to devise a method for maintaining the molar balance between diamine and adipic acid. Therefore, it is preferable to produce a polyamide 56 resin having an amino terminal group and a carbo terminal group in a well-balanced manner by a heat polymerization method, and to use for subsequent solid phase polymerization. More specifically, in the heat polymerization method, it is preferable to produce a polyamide 56 resin in which the amino terminal group concentration and the carboxyl terminal group concentration are in the relationship of the following formula, and subject to solid phase polymerization.
0.3 ≦ [NH ₂ ] / ([NH ₂ ] + [COOH]) ≦ 0.7
[NH ₂ ]: Amino end group concentration (eq / ton) in polyamide 56 resin subjected to solid phase polymerization
[COOH]: Carboxyl end group concentration (eq / ton) in polyamide 56 resin used for solid phase polymerization
A more preferable polyamide 56 resin subjected to solid phase polymerization satisfies the relationship of the following formula.
0.4 ≦ [NH ₂ ] / ([NH ₂ ] + [COOH]) ≦ 0.6
The polyamide 56 resin produced by the heat polymerization method preferably has a relative viscosity of sulfuric acid of 2 to 2.9. By making the relative viscosity of sulfuric acid 2.9 or less, thermal decomposition due to polymerization delay and formation of basic amine can be suppressed. By setting the relative viscosity of sulfuric acid to 2 or more, it is possible to produce a polyamide 56 resin in which the discharge state of the polymer in the discharge step is stable and the pellet particle size is uniform. More preferably, it is 2.1-2.85, and 2.2-2.8 is still more preferable.

  In order to maintain the molar balance between 1,5-pentamethylenediamine and adipic acid in the late stage of polymerization, 1,5-pentamethylenediamine is charged excessively with respect to adipic acid at the start of polymerization and volatilized by heat polymerization 1 , 5-pentamethylenediamine is supplemented, and it is preferable to set the reach temperature and polymerization time of heat polymerization within a specific range and suppress volatilization of 1,5-pentamethylenediamine in heat polymerization. As a result of detailed studies by the inventors, it has been found that it is difficult to produce a polyamide 56 resin in which amino terminal groups and carboxyl terminal groups are present in a balanced manner only by these methods.

  As a result of further diligent studies by the present inventors, 1,5-pentamethylenediamine has particularly high hydrophilicity, and therefore has a characteristic that it easily volatilizes with the evaporation of water, so that the polymerization reaction hardly proceeds. It was found that when the aqueous solution containing the raw material was heated from the initial stage to evaporate the water, the volatilization amount of 1,5-pentamethylenediamine tends to be very large. Specifically, it has been found that if the liquid temperature exceeds 150 ° C. from the initial stage of polymerization, 1,5-pentamethylenediamine is particularly likely to volatilize accompanying the evaporation of water.

  Therefore, in the method for producing the polyamide 56 resin by the heat polymerization method, a raw material aqueous solution containing 55 to 80% by weight of the raw material monomer is prepared in the raw material adjustment step, and the temperature of the aqueous solution is set to 100 to 150 ° C. in the concentration step. It is preferable to concentrate the monomer to 80 to 95% by weight. Then, it is preferable to manufacture the polyamide 56 resin through a pressure increasing process, a pressure suppressing process, a pressure releasing process, a pressure reducing process, and a discharging process.

  By making the concentration of the raw material aqueous solution 55% by weight or more as described above, the amount of water evaporated in the subsequent concentration step is reduced, and the volatilization amount of 1,5-pentanediamine can be reduced.

  Here, the raw material monomer refers to a monomer constituting the polyamide 56 used in the present invention, and includes 1,5-pentamethylenediamine, adipic acid and other copolymerization components described above. The raw material monomer concentration is a value obtained by dividing the total weight of the raw material monomers by the weight of the aqueous solution and multiplying by 100. On the other hand, when the raw material monomer is 80% by weight or less, the temperature of the piping through which the aqueous solution flows can be suppressed to an appropriate range, which is a preferable embodiment from the viewpoint of heat resistance of the piping and energy consumption. The concentration of the raw material aqueous solution is more preferably 60 to 80% by weight, still more preferably 65 to 80% by weight.

  By the way, a salt made of 1,6-hexamethylenediamine and adipic acid, which is a general raw material of polyamide 66, is not so high in solubility in water. Therefore, if the concentration is too high, the salt recrystallizes and precipitates. I had a problem. Therefore, the salt concentration in the aqueous solution needs to be adjusted to about 50% by weight, and even if the concentration is 50% by weight or less, recrystallization occurs easily if the temperature of the aqueous solution is low. It was necessary. For this reason, it has been technically difficult to increase the aqueous salt solution in the raw material adjustment step. Surprisingly, however, it has been found that a salt of 1,5-pentamethylenediamine and adipic acid, which is a raw material of polyamide 56, is a salt having extremely high solubility in water. For example, a 50% by weight aqueous solution of an equimolar salt of 1,6-hexamethylenediamine and adipic acid, which is a raw material for polyamide 66 resin, starts recrystallization when the liquid temperature falls below 40 ° C. It was discovered that a 50% by weight aqueous solution of an equimolar salt of 1,5-pentamethylenediamine and adipic acid does not recrystallize even at a liquid temperature of 5 ° C. and maintains a uniform dissolved state. From these characteristics, it was found that a high concentration raw material aqueous solution can be prepared in advance, and the concentration can be increased without volatilizing 1,5-pentamethylenediamine.

  When the temperature of the aqueous solution in the raw material adjustment step is in the range of 10 to 70 ° C., the solubility of 1,5-pentamethylenediamine and adipic acid salt in water increases, and the energy consumption required to keep the piping line warm Is suppressed. The temperature of the aqueous solution is more preferably 20 to 60 ° C.

  The heat polymerization method used in the present invention preferably includes a step of concentrating the aqueous solution containing the raw material (concentration step) after the raw material adjustment step, and in this concentration step, the concentration of the aqueous solution is concentrated to 80 to 95% by weight. Then, it is preferable to use for a pressure | voltage rise process. By setting the concentration of the aqueous solution to 80% by weight or more, the volatilization amount of 1,5-pentanediamine in the polymerization step can be suppressed. On the other hand, by setting the concentration of the aqueous solution to 95% by weight or less, a prepolymer is easily generated in the pressure control step. For this reason, the concentration of the aqueous solution at the end of the concentration step is more preferably 83 to 93% by weight, and still more preferably 85 to 90% by weight.

  At this time, it is preferable to maintain the temperature of the aqueous solution at 100 to 150 ° C., and by concentrating in the temperature range, water can be actively evaporated while suppressing volatilization of 1,5-pentamethylenediamine. Become. The temperature of the aqueous solution is more preferably 100 to 140 ° C, still more preferably 100 to 130 ° C, and particularly preferably 100 to 120 ° C.

  For the same reason, it is preferable to adjust the valve of the polymerization can so as to maintain the pressure (gauge pressure) in the polymerization can at 0.05 to 0.5 MPa, and keep it at 0.1 to 0.4 MPa. Is a more preferred embodiment. The concentration time may be selected so that the concentration of the aqueous solution falls within the above range, but is preferably 0.5 to 5 hours.

  In the preferred heat polymerization method used in the present invention described above, the absolute amount of volatilized water is small because the concentration of the salt aqueous solution charged in the polymerization can is high, and the aqueous solution is at a relatively low temperature and slightly pressurized in the concentration step. Therefore, the amount of 1,5-pentamethylenediamine volatilized in the polymerization process can be greatly reduced. For this reason, in the heat polymerization method satisfying the above requirements, the ratio of the number of moles of 1,5-pentamethylenediamine and the number of moles of adipic acid present in the raw material aqueous solution in the raw material adjustment step is 0.95. By adjusting the conditions such as the temperature in the can, the pressure in the can and the treatment time in the pressure control step, the pressure release step and the pressure reduction step, the amino terminal group and the carboxyl terminal group can be adjusted as described above. Can be produced in a balanced manner.

  Moreover, by using together the amine compound copolymerizable with the polyamide 56 illustrated above, a carboxylic acid compound, etc., a polymerization reaction can be controlled and a terminal group can also be adjusted.

  In addition, accelerating the polymerization reaction is preferable for suppressing volatilization of 1,5-pentamethylenediamine, and therefore it is preferable to include a polymerization accelerator at any stage in the production process of the polyamide 56 resin. . As the polymerization accelerator, a phosphorus compound having a high polymerization acceleration effect and also having an action as a heat stabilizer is preferable, and phenylphosphonic acid is preferably used.

  Regarding the steps other than the above in the polymerization step, for example, known methods described in JP-A No. 2003-292612, JP-A No. 2004-075932 and the like can be adopted. explain.

  In the pressurization step, it is preferable to raise the pressure to the desired pressure in the pressure control step described later by making the inside of the polymerization system a closed system and heating the aqueous solution containing the raw material to generate water vapor. The time required for the pressure increase is preferably in the range of 0.1 to 2 hours. Thereby, the temperature in a superposition | polymerization can is raised uniformly and the cyclization reaction of 1, 5-pentamethylenediamine is also suppressed.

  In the pressure control step, it is preferable to heat the polymerization system while maintaining a constant pressure to generate a prepolymer. At this time, by setting the pressure in the can (gauge pressure) to 1 to 2 MPa, volatilization of 1,5-pentamethylenediamine is suppressed and a prepolymer is easily formed. The pressure inside the can may be adjusted by a technique such as adjusting the degree of opening and closing of the valve connected to the outside world. Moreover, it is preferable to set it as 180-280 degreeC, and, as for the temperature in a can, it is a more preferable aspect to set it as 200-270 degreeC.

  In the pressure releasing step, it is preferable to release the pressure in the polymerization can to normal pressure and to bring the temperature in the polymerization can to the melting point of the prepolymer or higher. By adjusting the time required for releasing the pressure within a range of 0.1 to 3 hours, 1,5-pentamethylenedidiamine remaining unreacted is hardly volatilized. The time required for releasing pressure is more preferably 0.2 to 2 hours, and further preferably 0.3 to 1 hour. For this reason, it is preferable to increase the temperature in the polymerization can over the melting point of the prepolymer over the above-mentioned time, specifically 220-270 ° C. The temperature is more preferably 230 to 260 ° C.

  In the decompression step, the thermal decomposition of the polymer can be suppressed by heating the temperature in the polymerization can above the melting point of the produced polymer. For this reason, it is preferable that the temperature in a superposition | polymerization can shall be 240-300 degreeC.

  In addition, when the pressure in the polymerization can is lowered, water generated by polycondensation can be removed out of the system, the reaction can easily proceed, and uniformity of the reaction can be maintained by setting the pressure under a moderate pressure. For this reason, it is preferable to adjust the pressure (gauge pressure) in the polymerization can in the range of -5 to -50 kPa. The polymerization time in the depressurization step may be selected within a range that results in a polyamide 56 resin having a desired sulfuric acid relative viscosity. However, by setting the polymerization time within the range of 0.1 to 2 hours, the thermal decomposition in the polymerization can is suitably performed. It can be suppressed.

  In the discharging step, an inert gas such as nitrogen may be injected into the polymerization can, the gauge pressure in the polymerization can may be increased to 0.1 to 2 MPa, and the polymer may be discharged. It is preferable to cool the discharged polymer with water and cut the pellet so as to have a pellet size preferable for solid phase polymerization as described later.

  Next, a preferred solid phase polymerization method will be described.

  The polyamide 56 resin has a characteristic that the crystallization speed is slower than that of the conventional polyamide 66 resin, and if the solid phase polymerization is started at a high temperature from the beginning, the pellets are partially fused or severe. In some cases, the solid phase polymerization does not proceed uniformly. For this reason, the polyamide 56 resin pellets obtained by the heat polymerization method can be dried and pre-crystallized over a period of 1 to 10 hours while stirring the pellets at a temperature in the can of 80 to 120 ° C. under reduced pressure or nitrogen flow. preferable.

  Thereafter, it is preferable to produce polyamide 56 resin having a desired relative viscosity of sulfuric acid by solid-phase polymerization for 1 to 48 hours under reduced pressure while stirring the pellets at a can internal temperature of 130 to 200 ° C. At this time, in order to proceed the solid phase polymerization uniformly between the outer layer and the inner layer of the pellet, it is preferable to reduce the pressure in the can to 399 Pa or less, and it is more preferable to reduce the pressure to 133 Pa or less. Further, it is preferable to gradually advance solid-phase polymerization while gradually increasing the temperature in the can, and the rate of temperature rise after the temperature in the can reaches 130 ° C. is preferably 1 to 20 ° C./hr. More preferably, it is set to 2 to 10 ° C./hr. And, the lower the maximum temperature reached in the can, the more preferable it is because the thermal decomposition in the solid phase polymerization process is suppressed, and as a result, a polyamide 56 filament having a narrow molecular weight distribution can be produced. For this reason, the temperature in the can in the solid phase polymerization is more preferably 195 ° C. or less, more preferably 190 ° C. or less, and particularly preferably 185 ° C. or less.

  Next, a method for producing the polyamide 56 fiber used in the present invention will be described.

  A spun yarn was formed using a polyamide 56 resin having a relative viscosity of sulfuric acid of 3 to 8 and Mw / Mn of 1.5 to 3 produced by the heat polymerization method and the solid phase polymerization method as described above. After solidifying the spun yarn with cooling air, after applying a non-hydrous oil agent and taking it up at a speed of 300 to 2000 m / min, at a draw ratio at which the tensile elongation of the obtained filament fiber is 10 to 30% The polyamide 56 filament fiber of the present invention can be produced by stretching and heat treatment at a final heat treatment roll temperature of 210 to 250 ° C., then relaxing at a relaxation ratio of 0.8 to 0.95 and winding. it can.

  Here, first, it is important to spin the polyamide 56 resin whose Mw / Mn is 3 or less while suppressing the thermal decomposition until the polyamide 56 resin is melted and spun. Therefore, it is preferable to subject the polyamide 56 resin to heat spinning to make the moisture content 1000 ppm or less and then to use it for melt spinning.

  By the way, in the normal polyamide 66, if the moisture content is excessively low, gelation in melt storage tends to be induced and yarn breakage tends to be caused. However, in the polyamide 56 resin, gelation is difficult to occur, and thermal deterioration in melt storage is suppressed. Therefore, the lower the moisture content, the better. The moisture content is more preferably 600 ppm or less, and still more preferably 10 to 400 ppm. The reason why the polyamide 56 resin is less likely to be gelled at the time of melt storage than the polyamide 66 resin is not clear, but is thought to be due to the short carbon number of the methylene chain to which the amino terminal group is bonded. That is, in the polyamide 66 resin, since the amino terminal group is bonded to the methylene chain having 6 carbon atoms, the molecular chain in the vicinity of the amino terminal is easily returned, and when it is thermally decomposed, the returned product is liberated to induce gelation. On the other hand, in the polyamide 56 resin, since the carbon number of the methylene chain is 5, it is estimated that gelation hardly occurs due to steric hindrance.

  For this reason, it is preferable that the spinning temperature in melt spinning is 260-310 degreeC. When the spinning temperature is 310 ° C. or lower, the thermal decomposition of the polyamide 56 resin can be suppressed. The spinning temperature is more preferably 300 ° C. or lower, and further preferably 295 ° C. or lower. On the other hand, when the spinning temperature is 260 ° C. or higher, the polyamide 56 exhibits sufficient melt fluidity, the discharge amount between the discharge holes is made uniform, and high-stretching becomes possible. The spinning temperature is more preferably 270 ° C. or higher, and further preferably 275 ° C. or higher.

  As described above, a preferable embodiment of the present invention is to use ultrafine fibers having an average fiber diameter of 0.1 to 10 μm of single fibers of the polyamide 56 fibers used. Examples of the method for producing the ultrafine fiber include a method of directly spinning the ultrafine fiber, and a fiber having a normal fineness and capable of generating the ultrafine fiber (hereinafter sometimes referred to as an ultrafine fiber generating fiber). Can be produced by spinning and then generating ultrafine fibers. Examples of the method using the ultrafine fiber-generating fiber include a method of removing sea components after spinning sea-island type fibers, and a method of spinning and splitting split-type fibers to make ultrafine fibers. Among these, in the present invention, it is preferable that the ultrafine fiber can be obtained easily and stably, and it is preferably produced by the sea-island type fiber or the split type fiber, and more preferably produced by the sea-island type fiber. is there.

  The sea-island type fiber as used in the present invention refers to a fiber that is in a sea-island state by combining or mixing two or more components at any stage. As a method for obtaining this sea-island type fiber, for example, (1) a method in which two or more component polymers are blended and spun in a chip state, and (2) a two or more component polymer is kneaded in advance to form a chip and then spun. A method, (3) a method of mixing two or more polymers in a melted state with a static kneader or the like in a spinning machine pack, and (4) Japanese Patent Publication Nos. 44-18369, 54-116417, etc. Examples include a method of manufacturing using a die. Among these, the method (4) is preferably employed because it is easy to select a polymer and is excellent in the uniformity and dispersibility of the ultrafine fiber diameter required for high precision polishing.

  In the method (4), it is important that the island component polymer of the sea-island fiber is polyamide 56, and the sea component polymer is a copolymer obtained by copolymerizing polyethylene, polypropylene, polystyrene, sodium sulfoisophthalic acid, polyethylene glycol, or the like. Polymerized polyester, polylactic acid, and the like can be used. The number of polymer species to be used is preferably composed of two components, one sea component and one island component, in view of spinning stability. At this time, in order to prevent the island fibers from joining in the sea-island fibers, the weight ratio of the island fibers to the sea-island fibers is set to 0.99 or less, preferably 0.97 or less, preferably 0.8. The following is preferable. For the purpose of reducing the amount of sea component removed, the weight ratio of island fibers to sea-island fibers is set to 0.1 or more, preferably 0.2 or more, more preferably 0.4 or more. Examples of the cross-sectional shape of the island fiber obtained by removing the sea component polymer of the sea-island fiber include a circle, a polygon, Y, H, X, W, C, a rice field, and a π-type.

  Next, the process of forming a sheet-like material using the polyamide 56 fibers thus obtained will be described.

  As a method for obtaining a nonwoven fabric which is a preferable form of the sheet-like material to be the abrasive cloth of the present invention, a method of entanglement of a fiber web with a needle punch or a water jet punch, a spunbond method, a melt blow method, a paper making method, etc. are adopted. Among them, a method of undergoing a treatment such as a needle punch or a water jet punch is preferably used in order to further entangle the fibers.

  For a nonwoven fabric as a sheet-like material, a woven or knitted fabric may be laminated and integrated therewith, and a method in which the nonwoven fabric and the woven or knitted fabric are laminated and integrated by needle punching, water jet punching or the like is preferably used.

  In the needle punching process, the number of barbs on the needle is preferably 1 to 9 / bar. By making the number of barbs of the needle 1 or more, efficient fiber entanglement becomes possible. Further, when the number of barbs is 9 or less, fiber damage can be suitably suppressed. The total depth of the barb is preferably 0.05 to 0.09 mm. By setting the total depth to 0.05 mm or more, a sufficient catch on the fiber bundle can be obtained, so that efficient fiber entanglement is possible. Further, by making the total depth 0.09 mm or less, fiber damage can be suitably suppressed.

The number of punching is preferably 1000-7500 / cm ² . By setting the number of punching to 1000 pieces / cm ² or more, denseness can be obtained and a suitable finish with high accuracy can be obtained. Moreover, deterioration of workability, fiber damage, and strength reduction can be suitably prevented by setting the number of punching to 7500 pieces / cm ² or less.

  In addition, when woven and knitted fabric and nonwoven fabric are laminated and integrated, the needle barb direction during lamination is 90 ± 15 ° perpendicular to the traveling direction of the sheet, so that wefts that are easily damaged are hooked. It becomes difficult.

  Moreover, when performing a water jet punch process, it is preferable to perform water in the state of a columnar flow. Specifically, water can be ejected from a nozzle having a diameter of 0.05 to 1.0 mm at a pressure of 1 to 60 MPa.

  From the viewpoint of densification, the nonwoven fabric obtained in this way is preferably shrunk by dry heat or wet heat or both, and further densified.

  In the case of using ultrafine fiber generation type fibers, as a solvent for dissolving an easily soluble polymer (sea component) in order to generate ultrafine fibers, if the sea component is a polyolefin such as polyethylene or polystyrene, an organic material such as toluene or trichloroethylene is used. If a solvent is used and the sea component is polylactic acid or a copolyester, an aqueous alkali solution such as sodium hydroxide can be used. Further, 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 ultrafine fiber generation processing, known apparatuses such as a continuous dyeing machine, a vibro-washer type seawater removal machine, a liquid dyeing machine, a Wins dyeing machine, and a jigger dyeing machine can be used.

  Further, in order to improve the surface form, the strength and elongation and the cushioning property of the polishing cloth of the present invention, it is a preferable form to contain an elastic polymer in the sheet-like material, It may be applied before the ultrafine fiber generation processing described above, or may be applied after the ultrafine fiber generation processing.

  N, N′-dimethylformamide, dimethyl sulfoxide, or the like is preferably used as a solvent used when polyurethane is imparted as an elastic polymer, but a water-dispersed polyurethane liquid in which polyurethane is dispersed as an emulsion in water may be used. .

  The elastic polymer is applied to a base material such as a non-woven fabric by immersing the non-woven fabric in an elastic polymer solution dissolved in a solvent, and then dried to substantially solidify and solidify the elastic polymer. In the case of a solvent-based polyurethane solution, it can be solidified by immersing it in an insoluble solvent, and in the case of a water-dispersed polyurethane liquid having gelling properties, a dry coagulation method for drying after gelation, etc. Can be solidified. In drying, the fiber entangled body and the elastic polymer may be heated at a temperature that does not impair the performance.

  The polishing cloth of the present invention may be napped at least on one side by napping treatment. The napping treatment can be performed using sandpaper, a roll sander or the like. In particular, by using sandpaper, uniform and dense napping can be formed. Furthermore, in order to form uniform napping on the surface of the polishing pad, it is preferable to reduce the grinding load. In order to reduce the grinding load, for example, it is more preferable that the number of buffing stages is multistage buffing with three or more stages, and the number of sandpaper used in each stage is in the range of 150 to 600 of JIS regulations. It is.

  Since the polishing cloth of the present invention is excellent in water absorption, water absorption retention and uniform water absorption, polishing cloth for hard disk texture processing, polishing cloth for hard disk surface finishing, precision equipment such as silicon wafer and optical glass, etc. It is suitably used as a polishing cloth for finishing, and as a wiping cloth utilizing high water absorption.

  Specifically, the polishing cloth of the present invention is, for example, a polishing cloth for high precision polishing used for finishing precision equipment such as recording media, integrated circuit boards, and optical components, and is a polishing cloth for texture processing of hard disks. It is suitable for polishing cloths for surface finishing of hard disks and precision cloths such as silicon wafers and optical glass.

  Hereinafter, the present invention will be described in detail with reference to examples. The following methods were used for measurement and evaluation in the examples.

(1) Sulfuric acid relative viscosity 0.25 g of a sample was dissolved to 100 g of sulfuric acid having a concentration of 98% by weight, and the flow time (T1) at a temperature of 25 ° C. was measured using an Ostwald viscometer. did. Subsequently, the flow-down time (T2) of only 98% by weight sulfuric acid was measured. The ratio of T1 to T2, that is, T1 / T2, was defined as sulfuric acid relative viscosity.

(2) Mw / Mn
The sample was washed with hot water at a temperature of 90 ° C. for 30 minutes and then vacuum-dried at a temperature of 90 ° C. to obtain a moisture content of 1000 ppm, which was dissolved in hexafluoroisopropanol to obtain a measurement solution. This was measured by gel permeation chromatography (GPC), the weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined in terms of PMMA, and Mw / Mn was determined. The measurement conditions are as follows.
GPC device: Waters 510
-Column: Two Shodex GPC HFIP-806Ms connected together and used-Solvent: Hexafluoroisopropanol-Temperature: 30 ° C
・ Flow rate: 0.5 ml / min ・ Sample concentration: 2 mg / 4 ml
Filtration: 0.45 μm-DISMIC 13HP (Toyo filter paper)
・ Injection volume: 100 μl
Detector: differential refractometer RI (Waters 410)
Standard: PMMA (concentration: sample 0.25 mg / solvent 1 ml)
Measurement time: 62 minutes.

(3) Amino end group concentration 1 g of a sample was dissolved in 50 mL of a phenol / ethanol mixed solution (phenol / ethanol = 80/20) by shaking at a temperature of 30 ° C., and this solution was diluted with 0.02N hydrochloric acid. The amount of 0.02N hydrochloric acid required for neutralization titration was determined. Further, only the phenol / ethanol mixed solvent (the same amount as above) was neutralized and titrated with 0.02N hydrochloric acid to determine the amount of 0.02N hydrochloric acid required. And the amino terminal group amount per 1 ton of a sample was calculated | required from the difference.

(4) Carboxyl end group concentration 0.5 g of a sample was dissolved in 20 ml of 196 ± 1 ° C. benzyl alcohol, and this solution was neutralized and titrated with a 0.02N potassium hydroxide ethanol solution. Determine the amount of ethanol solution. In addition, only 20 ml of the benzyl alcohol was neutralized and titrated with a 0.02N potassium hydroxide ethanol solution to determine the amount of 0.02N potassium hydroxide ethanol solution required. And the amount of carboxyl end groups per 1 ton of a sample was calculated | required from the difference.

(5) Moisture content Using a Karl Fischer coulometric titration moisture meter (Hiranuma Sangyo Co., Ltd. trace moisture measuring device AQ-2000 and the company's moisture vaporizer EV-200), dry nitrogen gas was flowed at a moisture vaporization temperature of 180 ° C. Measured.

(6) Basis / Thickness / Apparent Density of Polishing Cloth The basis weight (g / m ² ) was measured by the method of JIS L1096 8.4.2 (1999), and dial thickness gauge (manufactured by Ozaki Mfg. Co., Ltd., trade name “ The thickness (mm) was measured by Peacock H ″ (registered trademark). The apparent fiber density (g / cm ² ) was determined from the basis weight and thickness values by calculation.

(7) Average fiber diameter of single fiber A cross section perpendicular to the thickness direction of the polishing cloth was observed with a scanning electron microscope (SEM) at a magnification of 3000 times, and 50 single fibers randomly selected within a 30 μm × 30 μm visual field. The fiber diameter was measured. This was performed at three locations, the diameters of a total of 150 single fibers were measured, and the average value was calculated by rounding off the numbers after the decimal point. When the ultrafine fiber has a deformed 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 regarded as a circle.

(8) Fineness of single fiber The single fiber extracted from the sheet-like material was measured for specific gravity according to JIS K0061 (2001), the density stir tube method of 8.3. It calculated | required by calculating the fineness (dtex) from the specific gravity of the calculated | required fiber polymer, and the average fiber diameter calculated | required by said (7).

(9) Tensile strength JIS L1017 (1995), Tensile strength and elongation of 7.5, (1) Tensilon UCT-100 manufactured by Orientec Co., Ltd. is used according to the measurement method of the standard time test. Then, the SS curve of the single fiber extracted from the sheet-like material was measured. Prior to the measurement, the sample was conditioned for 48 hours in an environment of room temperature 25 ° C. and relative humidity 55% under no load. Then, in the same environment, the SS curve was measured with an initial load of 0.08 cN / dtex, a sample length of 20 mm, and a tensile speed of 20 mm / min. The tensile strength was determined by dividing the strength at the point showing the maximum strength in the SS curve by the fineness determined by the fineness of the single fiber of (8) above.

(10) Tensile strength of sheet-like material According to JIS L1096 8.12.1 (1999), a sample having a width of 5 cm and a length of 20 cm is taken from the sheet-like material, and a constant-speed extension type tensile tester with a gripping interval of 10 cm. The sample was stretched at a tensile speed of 10 cm / min. From the obtained value, the load per 1 cm width was defined as the tensile strength (N / cm). Moreover, the stress at the time of 1 cm elongation was defined as the stress at 10% elongation.

(11) Water drop absorption time Using a FACE / CA-A type contact angle assumption device (manufactured by Kyowa Interface Science Co., Ltd.), distilled water is put into a syringe and an injection needle (outer diameter 0.60 mm, inner diameter 0.45 mm). 1 drop of water was dropped into a polishing cloth, the water drop was observed from the eyepiece of the device, and the water absorption time (tq) was determined from the following equation.
tq = t2-t1 (seconds)
(Wherein, t1 is the time when the water droplet fell on the polishing cloth, and t2 is the time when the water droplet was sucked into the polishing cloth and there was no water drop on the surface.)

  The state of t1 and t2 can be visually observed in a normal case (approximately tq is 10 seconds or more), but when it is very early or difficult to observe, water droplets start dropping from the injection needle with the aforementioned device. The time until the water droplet is sufficiently absorbed by the polishing cloth is measured after video recording of all the images of the water droplet state through the eyepiece of the apparatus. This was performed at 20 locations, and the average value of the 5 largest data among the measured values at 20 locations was taken, and this average value was taken as the water droplet absorption time. It shows that water absorption is so high that water absorption time is short.

(12) Water drop contact angle Using the same apparatus as in (11) above, the measurement was performed in an environment suitable for a liquid at a temperature of 20 ° C and a humidity of 60%. Similarly to the measurement of the water absorption time, measurements were made at 20 locations, and the average value of the 5 largest data among the measured values at 20 locations was taken, and the average value was taken as the water droplet contact angle. The smaller the water droplet contact angle, the higher the hydrophilicity, indicating that the slurry is uniformly dispersed on the surface of the polishing pad.

(13) Polishing evaluation As a tape-like polishing cloth in which each polishing cloth was cut into a width of 40 mm with respect to an underlying plating substrate (substrate) having a surface roughness of 1.2 angstroms, which was subjected to Ni-P plating on aluminum and polished. Using a texture device (manufactured by Hitachi DECO), polishing was performed using a slurry liquid containing about 0.2 wt% of polycrystalline diamond having an average particle diameter of 50 nm and a coolant. The polishing conditions are: the substrate rotation speed is 50 rpm, the substrate oscillation frequency is 5 Hz, the pressing pressure of the tape-like polishing cloth is 500 gf, the moving speed of the tape-like polishing cloth is 40 mm / min, and the supply amount of the slurry is 15 ml / min. did. The polishing time was 15 sec per sheet for both sides simultaneously.

(14) Substrate surface roughness after polishing The substrate polished in (13) above was observed using an atomic force microscope (AFM) at a scanning speed of 10 μm / sec and a scanning number of 256 in a 10 μm × 10 μm field of view. The arithmetic average roughness (Ra) was calculated. This was measured at 3 locations for each disc, 3 discs, a total of 9 locations, and the average value of 9 data was taken, and the average value was taken as the surface roughness.

(15) Number of substrate scratches after polishing Using both Candela 5100 optical surface analyzer as a measurement object on both surfaces of the five substrates polished in (13) above, that is, a total of 10 surfaces, a groove having a depth of 2 nm or more was scratched, The number of scratches was measured, and the average value of the measured values on the 10 surfaces was evaluated.

<Adjustment Example 1> (Adjustment of lysine decarboxylase)
E. E. coli strain JM109 was cultured as follows. First, this platinum strain was inoculated into 5 ml of LB medium, and precultured by shaking at 30 ° C. for 24 hours. Next, 50 ml of LB medium was put in a 500 ml Erlenmeyer flask and steam sterilized at a temperature of 115 ° C. for 10 minutes in advance. The strain was precultured in this medium, and cultured for 24 hours under the condition of 30 cm in amplitude and 180 rpm while adjusting the pH to 6.0 with 1N aqueous hydrochloric acid. The bacterial cells thus obtained were collected and a cell-free extract was prepared by ultrasonic disruption and centrifugation. Measurement of these lysine decarboxylase activities was carried out according to a standard method (Kenji Yokota, Haruo Misono, Biochemistry Experiment Course, vol.11, P.179-191 (1976)).

  When lysine is used as a substrate, conversion by lysine monooxygenase, lysine oxidase and lysine mutase, which are considered to be the main main pathways, can occur. Therefore, for the purpose of blocking this reaction system, E. coli is treated at a temperature of 75 ° C. for 5 minutes. The cell-free extract of E. coli strain JM109 was heated. Furthermore, this cell-free extract was fractionated with 40% saturated and 55% saturated ammonium sulfate. Using this crude purified lysine decarboxylase solution, 1,5-pentamethylenediamine was produced from lysine.

<Adjustment Example 2> (Adjustment of 1,5-pentamethylenediamine)
An aqueous solution prepared to be 50 mM lysine hydrochloride (manufactured by Wako Pure Chemical Industries), 0.1 mM pyridoxal phosphate (manufactured by Wako Pure Chemical Industries) and 40 mg / L-crudely purified lysine decarboxylase (manufactured in Preparation Example 1) While maintaining the pH at 5.5 to 6.5 with a 0.1N hydrochloric acid aqueous solution, the mixture was reacted at a temperature of 45 ° C. for 48 hours to obtain 1,5-pentamethylenediamine hydrochloride. By adding sodium hydroxide to this aqueous solution, 1,5-pentamethylenediamine hydrochloride is converted to 1,5-pentamethylenediamine, extracted with chloroform, and distilled under reduced pressure (1.33 kPa, 60 ° C.). As a result, 1,5-pentamethylenediamine was obtained.

<Preparation Example 3> (Preparation of 50% by weight aqueous solution of 1,5-pentamethylenediamine and adipic acid salt)
An aqueous solution obtained by dissolving 102 g of 1,5-pentamethylenediamine prepared in Preparation Example 2 in 248 g of water is immersed in a water bath at a temperature of 50 ° C. and stirred. 1 g was added in the vicinity of the neutralization point, and about 0.2 g was added. The change in pH of the aqueous solution relative to the amount of adipic acid added was examined, and the neutralization point was determined to be pH 8.32. The amount of adipic acid added at the neutralization point was 146 g. A 50% by weight aqueous solution (496 g) of an equimolar salt of 1,5-pentamethylenediamine and adipic acid was adjusted so that the pH was 8.32.

<Preparation Example 4> (Preparation of 70% by weight aqueous solution of 1,5-pentamethylenediamine and adipic acid salt)
70% by weight aqueous solution of an equimolar salt of 1,5-pentamethylenediamine and adipic acid (354.3 g) in the same manner as in Preparation Example 3, except that the amount of water in Preparation Example 3 was 104.3 g. Adjusted.

<Preparation Example 5> (Preparation of 57% by weight aqueous solution of 1,5-pentamethylenediamine and adipic acid salt)
57% by weight aqueous solution of an equimolar salt of 1,5-pentamethylenediamine and adipic acid (435.1 g) in the same manner as in Preparation Example 3, except that the amount of water in Production Example 3 was 187.1 g. Adjusted.

[Example 1]
While adjusting the 70% by weight aqueous solution of the equimolar salt of 1,5-pentamethylenediamine and adipic acid of Preparation Example 4 to a temperature of 50 ° C., 1,5-pentamethylenediamine and water were added to the aqueous solution. The ratio of the number of moles of 1,5-pentamethylenediamine to the number of moles of adipic acid (number of moles of 1,5-pentamethylenediamine / number of moles of adipic acid) is 1.007, and the concentration of the raw material in the aqueous solution Was adjusted to 70% by weight. Further, phenylphosphonic acid was added to the raw material aqueous solution so that 100 ppm of phosphorus atoms was contained in the obtained polyamide 56 resin, and then charged in a heating medium heating polymerization kettle previously substituted with nitrogen (raw material adjustment step).

  Next, the aqueous medium was concentrated by heating the heating medium while purging the inside of the can with nitrogen (concentration step). At this time, the internal temperature of the can was set to 125 ° C., and the internal pressure (gauge pressure) was controlled to 0.2 MPa, and the raw material in the aqueous solution was concentrated to 90% by weight. The concentration of the aqueous solution in the can was judged from the amount of distilled water.

  Next, the polymerization kettle was sealed, the heating medium temperature was increased to 270 ° C., and the pressure was increased until the pressure in the can (gauge pressure) reached 1.7 MPa (pressure increasing step). Thereafter, the internal pressure of the can (gauge pressure) was controlled at 1.7 MPa and maintained until the internal temperature of the can reached 250 ° C. (controlling process). Furthermore, the heat medium temperature was changed to 285 ° C., and the pressure was released to atmospheric pressure over 60 minutes (pressure release process). Further, the pressure in the can (gauge pressure) was reduced to −13.3 kPa, and the polymerization reaction was stopped when the predetermined stirring power was reached (decompression step).

The obtained polyamide 56 resin had a sulfuric acid relative viscosity of 2.75, and [NH ₂ ] / ([NH ₂ ] + [COOH]), which is an index of the balance between the amino end group concentration and the carbo end group concentration, was 0.48. Met.

  The obtained polyamide 56 resin was charged into a vacuum dryer type vacuum dryer, and a copper acetate 5 wt% aqueous solution was added as copper atoms to 100 ppm with respect to the polyamide 56 resin, and the dryer was rotated for about 1 hour. Blended. And 50 weight% potassium iodide aqueous solution was added as a potassium atom so that it might become 600 ppm with respect to the polyamide 56 resin, the drier was rotated again, and it blended for about 1 hour. Thereafter, while the resin in the can was stirred by rotating the dryer, the temperature in the can was raised to 90 ° C. under a nitrogen flow, and the temperature in the can was maintained at 90 ° C. for 5 hours for precrystallization.

  Next, after the supply of nitrogen is stopped and the pressure reduction in the can is started, the temperature in the can is again raised, and after the temperature in the can reaches 130 ° C., the rate of temperature rise is 5 ° C./hour. The temperature inside the can was raised to 170 ° C. while controlling the heater output. Then, after maintaining for a predetermined time under conditions of a can internal temperature of 170 ° C. and a can internal pressure of 133 Pa or less, the polyamide 56 resin was extracted. At this time, the holding time under the condition of a can internal pressure of 133 Pa or less was adjusted so that the obtained polyamide 56 resin had a sulfuric acid relative viscosity of 3.85. That is, a polyamide 56 resin having a different retention time was produced, a correlation curve between the sulfuric acid relative viscosity and the retention time of the obtained polyamide 56 resin was determined, and the retention time at which the sulfuric acid relative viscosity was 3.85 was determined.

  The obtained polyamide 56 resin had a sulfuric acid relative viscosity of 3.85, Mw / Mn of 2.17, and a moisture content of 300 ppm.

  Using the obtained polyamide 56 resin as an island component and copolymer polystyrene (co-PSi) copolymerized with 22 mol% of 2-ethylhexyl acrylate as a sea component, a 36 island / hole sea-island type compound spinneret was used for spinning. Melt spinning was performed at a temperature of 275 ° C., an island / sea mass ratio of 40/60, a discharge rate of 1.6 g / min · hole, and a spinning speed of 1200 m / min. Next, it is stretched 3.0 times in a liquid bath at a temperature of 85 ° C., crimped using an indentation type crimping machine, cut, sea island with a fineness of 4.2 dtex and a fiber length of 51 mm A raw cotton of type composite fiber was obtained.

A laminated web was formed through the card and cross wrapping process using the obtained raw material of sea-island type composite fiber. Next, using a needle punch machine in which one needle having a total barb depth of 0.08 mm was implanted, the needle depth was 7 mm, the number of punches was 3000 / cm ² , the basis weight was 695 g / m ² , and the apparent density was A non-woven fabric of 0.23 g / cm ³ was produced.

  The obtained non-woven fabric was subjected to hot water shrinkage at a temperature of 95 ° C., and then 34% by mass of polyvinyl alcohol was added to the mass of the fiber, followed by drying. Then, it processed with trichlorethylene, the sea component of the sea-island type composite fiber was dissolved and removed, and the nonwoven fabric which consists of an ultrafine fiber of the polyamide 56 was obtained.

  Polyamide 56 is obtained in this way, the polymer diol is a polyurethane comprising 75% by mass of a polyether and 25% by mass of a polyester, and 25% by mass of the solid content with respect to the mass of the fiber. The polyurethane was coagulated with a 30% DMF aqueous solution having a liquid temperature of 35 ° C., and DMF and polyvinyl alcohol were removed with hot water having a temperature of about 85 ° C. Thereafter, the sheet is cut in half in the thickness direction by a half-cutting machine having an endless band knife, and the non-half-cut surface is ground in three stages using a JIS # 320 sandpaper to form napped fibers, and a sheet made of polyamide 56 ultrafine fiber and polyurethane A product was produced. The evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1, and showed excellent water absorption and good polishing performance.

[Example 2]
In Example 1, 1,5-pentamethylenediamine and 1,5-pentamethylenediamine prepared in Preparation Example 5 were mixed with 57% by weight of an equimolar salt of adipic acid at a water temperature of 50 ° C. And the ratio of the number of moles of 1,5-pentamethylenediamine and the number of moles of adipic acid present in the aqueous solution (number of moles of 1,5-pentamethylenediamine / number of moles of adipic acid) is 1.007. A polyamide 56 resin was obtained by performing heat polymerization in the same manner as in Example 1 except that the concentration of the raw material monomer in the aqueous solution was adjusted to 57% by weight.

  The obtained polyamide 56 resin has a sulfuric acid relative viscosity of 2.75, and [NH2] / ([NH2] + [COOH]), which is an index of the balance between the amino end group concentration and the carbo end group concentration, is 0.33. there were.

  This polyamide 56 resin was subjected to solid phase polymerization in the same manner as in Example 1, and then a sheet-like material composed of polyamide 56 ultrafine fibers and polyurethane was produced in the same manner as in Example 1. The evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1, and showed excellent water absorption and good polishing performance.

[Example 3]
In Example 1, except that the number of islands of the spinneret used at the time of spinning the sea-island type composite fiber was 376 islands / hole, a sheet-like material composed of polyamide 56 ultrafine fibers and polyurethane was produced in the same manner as in Example 1. did. The evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1, and showed excellent water absorption and good polishing performance.

[Example 4]
In Example 1, a polyamide 56 ultrafine fiber was obtained in the same manner as in Example 1 except that the basis weight of the nonwoven fabric obtained from the raw cotton of the sea-island type composite fiber was 1045 g / m ² and the apparent density was 0.22 g / cm ^3. A sheet-like material made of polyurethane was prepared. The evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1, and showed excellent water absorption and good polishing performance.

[Comparative Example 1]
A heating medium heating polymerization kettle previously substituted with nitrogen was charged with a 50% by weight aqueous solution of an equimolar salt of 1,5-pentamethylenediamine and adipic acid obtained in Preparation Example 3, and the heating medium temperature was set to 280 ° C. Then heating was started. The pressure in the polymerization can is adjusted to 1.47 MPa, the contents are heated to a temperature of 270 ° C., then the pressure in the can is gradually released, and the pressure (gauge pressure) in the polymerization can is further reduced to −13. After reducing the pressure to 3 kPa, the polymerization reaction was stopped when the predetermined stirring power was reached, and the discharged strand was cooled with water and cut to obtain a polyamide 56 resin having a sulfuric acid relative viscosity of 3.72. In Comparative Example 1, since the polyamide 56 resin having a relative viscosity of sulfuric acid of 3 or more was produced only by the heat polymerization method, the pressure (gauge pressure) in the polymerization can reached -13.3 kPa to reach the predetermined stirring power. It was necessary to lengthen the holding time as 3 hours from the beginning. Mw / Mn of the obtained polyamide 56 resin is 3.2, which has a wide molecular weight distribution, and [NH ₂ ] / ([NH ₂ ] + [], which is an index of the balance between amino terminal group concentration and carbo terminal group concentration. COOH]) was as low as 0.15, and the molar balance in the polymerization can was broken.

  The obtained polyamide 56 resin was vacuum dried at a can internal temperature of 90 ° C. using a vacuum dryer type dryer, and dried until the water content of the polymer after drying was 300 ppm.

  Using the obtained polymer, in the same manner as in Example 1, a sheet-like product composed of polyamide 56 ultrafine fibers and polyurethane was produced. The evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1. Compared with Example 1, the polishing performance was poor. Further, fiber dropping due to fiber breakage was observed in the sheet-like material after polishing. This is probably because the dropped fibers became a foreign substance during polishing and had an adverse effect.

[Comparative Example 2]
In Example 1, the polyamide 56 resin obtained by heat polymerization was not subjected to solid phase polymerization, and vacuum drying was performed at 90 ° C. in a can with a vacuum dryer type dryer, and the moisture content of the polymer after drying was 300 ppm. Dried until

  Using the obtained polymer, in the same manner as in Example 1, a sheet-like product composed of polyamide 56 ultrafine fibers and polyurethane was produced. The evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1. Compared with Example 1, the polishing performance was poor. Further, fiber dropping due to fiber breakage was observed in the sheet-like material after polishing.

[Comparative Example 3]
The ratio of the number of moles of 1,6-hexamethylenediamine and the number of moles of adipic acid (the number of moles of 1,6-hexamethylenediamine / the number of moles of adipic acid) was measured in a heating medium heating polymerization kettle previously substituted with nitrogen. The aqueous solution was 1.007, the concentration of the raw material monomer in the aqueous solution was 50% by weight, and the water temperature was 50 ° C. The heating medium temperature was set to 280 ° C. and heating was started. The pressure inside the polymerization can is adjusted to 1.47 MPa, the contents are heated to 270 ° C., then the pressure inside the can is gradually released, and after further reducing the pressure, the polymerization reaction is performed when the predetermined stirring power is obtained. Was stopped, and the discharged strand was cooled with water and cut to obtain a polyamide 66 resin.

The obtained polyamide 66 resin has a sulfuric acid relative viscosity of 2.85, and [NH ₂ ] / ([NH ₂ ] + [COOH]), which is an index of the balance between the amino end group concentration and the carbo end group concentration, is 0.42. ,Met.

  The obtained polyamide 66 resin was charged into a vacuum dryer type vacuum dryer, and a copper acetate 5 wt% aqueous solution was added as copper atoms to 100 ppm with respect to the polyamide 66 resin, and the dryer was rotated for about 1 hour. Blended. And 50 weight% potassium iodide aqueous solution was added as a potassium atom so that it might become 600 ppm with respect to polyamide 66 resin, the drier was rotated again, and it blended for about 1 hour. Then, after the pressure in the can was started while stirring the resin in the can by rotating the dryer, the temperature in the can was raised again, and the temperature in the can was raised to 170 ° C. Then, after reaching a temperature of 170 ° C., the pressure in the can was maintained at 133 Pa or less for a predetermined time, and then the polyamide 66 resin was extracted. At this time, the holding time at a can internal pressure of 133 Pa or less was adjusted so that the obtained polyamide 66 resin had a sulfuric acid relative viscosity of 3.85. That is, a polyamide 66 resin having a different retention time was produced, and a correlation curve between the relative viscosity of sulfuric acid and the retention time of the obtained polyamide 66 resin was determined, and the retention time at which the sulfuric acid relative viscosity was 3.85 was determined. The obtained polyamide 66 resin had a sulfuric acid relative viscosity of 3.85 and Mw / Mn of 2.2.

  Thereafter, the moisture content of the obtained polyamide 66 resin was adjusted to 600 ppm, and in the same manner as in Example 1, a sheet-like product composed of polyamide 66 ultrafine fibers and polyurethane was produced. However, the spinning temperature was 280 ° C. The evaluation results of the polyamide 66 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1. Compared with Example 1, both water absorption and polishing performance were inferior.

[Comparative Example 4]
An 80-liter stainless steel autoclave was charged with 25 kg of an ε-caprolactam aqueous solution (containing 15% water), the inside of the can was purged with nitrogen, and then sealed, and the internal pressure (gauge pressure) was 1.5 MPa until the temperature inside the can reached 255 ° C. The valve was adjusted so as not to exceed the temperature, and the temperature was raised while heating to advance the polymerization reaction. After the internal temperature of the can reached 250 ° C., the internal pressure of the can was gradually released to atmospheric pressure, and then polymerization was continued while supplying nitrogen (5 liters / minute), and the polymerization reaction was stopped with a predetermined stirring power. . The inside of the polymerization can was slightly pressurized with nitrogen to discharge the polymer, and then cooled with water and cut. The obtained polyamide 6 resin was treated with hot water at a temperature of 95 ° C. for 10 hours in order to remove low molecular weight components to obtain a polyamide 6 resin.

  The obtained polyamide 6 resin was vacuum dried using a vacuum dryer type dryer at a can internal temperature of 90 ° C. and dried until the water content of the polymer after drying was 400 ppm. Thus, a sheet-like material made of polyamide 6 ultrafine fibers and polyurethane was produced. However, the spinning temperature was 260 ° C. The evaluation results of the polyamide 6 ultrafine fibers extracted from the obtained sheet-like material and the obtained sheet-like material are as shown in Table 1. Compared with Example 1, both water absorption and polishing performance were inferior.

[Example 5]
The single fiber fineness was 4.1 dtex in the same manner as in Example 1 except that the island component polymer and the sea component polymer of Example 1 were used and chip blending was performed at a mass ratio of island component / sea component = 40/60. There was obtained a raw cotton of a sea-island type composite fiber having a fiber length of 51 mm. A sheet-like material composed of polyamide 56 ultrafine fibers and polyurethane was prepared in the same manner as in Example 1 except that the obtained raw cotton was used. Table 1 shows the evaluation results of the polyamide 56 ultrafine fibers extracted from the obtained sheet and the obtained sheet.

[Example 6]
Using the nonwoven fabric made of the ultrafine fiber of polyamide 56 obtained in Example 1, the polyurethane was not attached, and was cut in the thickness direction by a half-cutting machine having an endless band knife.

  The obtained semi-cut nonwoven fabric was sprayed with a pressure water stream to the surface layer side from a nozzle having 0.1 mmφ holes at intervals of 0.6 mm to entangle the ultrafine fibers and simultaneously remove polyvinyl alcohol. The treatment speed was 5 times at 5 m / min, and the water pressure during the 5 treatments was 17 MPa, 17 MPa, 17 MPa, 10 MPa, and 7 MPa, respectively. Next, the non-semi-finished surface was ground in three steps using a JIS # 320 sandpaper to form napped fibers, thereby producing a sheet-like material composed only of polyamide 56 ultrafine fibers. The evaluation results of the obtained sheet-like material were as shown in Table 1, and showed excellent water absorption and good polishing performance.

Claims (5)

  90% by mole or more of the repeating units are composed of pentamethylene adipamide units, are composed of polyamide 56 having a relative viscosity of sulfuric acid of 3 to 8 and a molecular weight dispersity (Mw / Mn) of 1.5 to 3, A polishing cloth comprising a sheet-like material having a polyamide 56 fiber having a strength of 4 to 11 cN / dtex.   2. The polishing cloth according to claim 1, wherein the number average single fiber diameter of the polyamide 56 fibers is 0.1 to 10 [mu] m.   The abrasive cloth according to claim 1 or 2, wherein the sheet-like material comprises a nonwoven fabric.   The abrasive cloth according to any one of claims 1 to 3, wherein the sheet-like material contains an elastic polymer.   The abrasive cloth according to any one of claims 1 to 4, wherein the sheet-like product has a vertical or horizontal 10% elongation stress of 5 N / cm or more.