JP4420761B2 - Polishing sheet manufacturing method and polishing sheet - Google Patents

Description

  The present invention relates to a method for producing a polishing sheet and a polishing sheet. More specifically, the present invention relates to mirror polishing of a semiconductor wafer, a conductive layer of a semiconductor wafer in a multilayer wiring process or an element isolation process used as a substrate of a semiconductor integrated circuit, or The present invention relates to a polishing sheet manufacturing method and a polishing sheet that can be suitably used for chemical mechanical polishing for flattening an insulating film, precision polishing of a memory disk, a photochemical component lens, and the like.

  Conventionally, precision polishing of semiconductor wafers, memory disks, photochemical component lenses, etc. is performed by pressing the polishing sheet against the object to be polished and supplying a polishing liquid composed of abrasive grains and water, etc. This was done by relatively polishing the abrasive body. And as a manufacturing method of the abrasive | polishing sheet | seat used for such precision grinding | polishing, the method of wet coagulating after making the fiber sheet base material impregnate the organic solvent solution of a polyurethane resin is disclosed.

  For example, Japanese Patent No. 2740143 (Patent Document 1) discloses a method for producing a porous polishing pad material. The polishing sheet obtained by such a manufacturing method is a structure of fibers and polyurethane resin, and has many gaps. The polishing liquid can be held in the gaps, and polishing waste can be discharged through the gaps. It had the characteristics.

However, in such a production method, a polishing sheet is produced using an organic solvent solution of a polyurethane resin, but there is a problem that the production environment is poor because the organic solvent solution has high flammability and toxicity. Further, in such a production method, if the solvent (usually water) used in the wet coagulation step is discarded as it is, the global environment is deteriorated due to the organic solvent contained in the solvent. There is a problem that it takes a lot of time and effort because it becomes necessary to collect the wastewater.
Japanese Patent No. 2740143

  Here, in order to solve the above-described problems, it is conceivable to use a polishing sheet manufacturing method using an aqueous polyurethane that does not require recovery of an organic solvent with respect to the polishing sheet manufacturing method.

  However, in such a production method, since water-based polyurethane is dry-coagulated, it is necessary to evaporate water as a solvent by impregnating the fiber base material with water-based polyurethane and then drying by heating at 100 ° C. or higher. Along with the evaporation of water, the polyurethane also moves to both surfaces of the fiber substrate, which causes a problem of so-called migration. Therefore, although the manufactured polishing sheet has a sufficient amount of polyurethane fixed in the vicinity of both surfaces of the substrate, the amount of polyurethane fixed in the interior of the substrate (particularly in the vicinity of the center) is small or extreme. In some cases, the polishing sheet was hardly fixed, and the polyurethane was unevenly distributed. And, such a fixed polishing sheet has a problem that it is easy to wear and has a short life, and is also easily deformed by pressure and heat applied during polishing, and is used for precision polishing of semiconductor wafers, memory disks, photochemical component lenses, etc. Could not be used.

  The present invention has been made in view of the above-described problems of the prior art, and enables the water-based polyurethane resin to be fixed uniformly throughout the entire fiber base, has an appropriate hardness, is hard to wear, and has a long service life. In addition, it is possible to efficiently and reliably obtain a polishing sheet having excellent shape stability, and at the same time, a manufacturing method of a polishing sheet capable of solving problems of manufacturing environment and environmental pollution, and An object of the present invention is to provide a polishing sheet obtained by the production method.

  As a result of intensive studies to achieve the above object, the inventors of the present invention made a dry solution by impregnating a non-woven fabric with a specific aqueous polyurethane resin, a specific organic acid salt and water and then drying the mixture. It was found that an abrasive sheet having the aqueous polyurethane resin adhered uniformly to the inside of the nonwoven fabric was obtained without migration of the aqueous polyurethane resin inside, and the present invention was completed based on this finding. .

  That is, the method for producing a polishing sheet of the present invention comprises (A) a carboxyl group-containing polyurethane resin, (B) a mixed solution containing an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms and (C) water. After being impregnated with the material, it is dried to obtain a polishing sheet.

  As the liquid mixture used in the method for producing a polishing sheet of the present invention, the mixing ratio of (A) a carboxyl group-containing polyurethane resin and (B) an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is used. It is preferable that (A) :( B) = 100: 0.5 to 100: 20 in terms of solid content.

  The (A) carboxyl group-containing polyurethane resin used in the method for producing a polishing sheet of the present invention includes (a) an organic diisocyanate, (b) a polyol, and (c) a carboxyl group and two or more active hydrogens. And (d) a polyamine having two or more amino groups and / or imino groups after neutralizing a carboxyl group-containing isocyanate group-terminated prepolymer obtained by reacting a compound having the following formula: A carboxyl group-containing polyurethane resin obtained by a chain extension reaction using a compound is preferable.

  Moreover, as (A) carboxyl group containing polyurethane resin used for the manufacturing method of the polishing sheet | seat of this invention, content of the carboxyl group in (A) carboxyl group containing polyurethane resin is 0.5-4. It is preferably 0% by mass.

  Furthermore, the value of 100% modulus of the (A) carboxyl group-containing polyurethane resin used in the method for producing a polishing sheet of the present invention is preferably 10 to 25 MPa.

  The carboxylic acid having 1 to 4 carbon atoms used in the method for producing a polishing sheet of the present invention is preferably formic acid or acetic acid.

  Moreover, as said liquid mixture used for the manufacturing method of the polishing sheet | seat of this invention, it is preferable that pH value is 7.0-9.0 and coagulation | solidification temperature is 35-60 degreeC.

  Furthermore, the nonwoven fabric used in such a method for producing a polishing sheet of the present invention is preferably a nonwoven fabric composed of fibers having a titanium oxide content of 0.1% by mass or less.

  Moreover, it is preferable that it is a polyester fiber as said fiber used for the manufacturing method of such a polishing sheet of this invention.

  The polishing sheet of the present invention is a polishing sheet obtained by the production method of the present invention.

  According to the method for producing a polishing sheet of the present invention, polyurethane can be coagulated and fixed at a relatively lower temperature than the solvent water evaporates. A polishing sheet in which polyurethane is uniformly fixed over the entire substrate can be produced. In addition, according to the method for producing a polishing sheet of the present invention, it is possible to produce a polishing sheet that has an appropriate hardness, is hard to wear, has a long life, and is difficult to deform during polishing with high productivity. . In addition, since the aqueous polyurethane resin is used in the production method of the present invention, it becomes possible to reduce the recovery cost and labor of the organic solvent generated when the organic solvent solution of the polyurethane resin is used, and further, there is a risk of fire. It is possible to simultaneously solve the problems of performance, deterioration of work environment, and environmental pollution.

  In addition, since the polishing sheet of the present invention is obtained by the above-described production method, it is difficult to wear and has a long life, and since it is difficult to deform during polishing, it can be used for precise polishing.

  Therefore, according to the present invention, the water-based polyurethane resin can be uniformly fixed over the entire fiber base, has an appropriate hardness, is hard to wear, has a long life, and has excellent shape stability. A method for producing a polishing sheet capable of efficiently and reliably obtaining a sheet for use and capable of simultaneously solving problems of production environment and environmental pollution, and a polishing sheet obtained by the production method It becomes possible to provide.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  The polishing sheet manufacturing method of the present invention impregnates a nonwoven fabric with (A) a carboxyl group-containing polyurethane resin, (B) a mixed solution containing an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms and (C) water. Then, it is dried to obtain a polishing sheet.

  The (A) carboxyl group-containing polyurethane resin according to the present invention is a polyurethane resin containing a carboxyl group as a hydrophilic component in the urethane resin skeleton. As such (A) carboxyl group-containing polyurethane resin, (a) an organic diisocyanate, (b) a polyol, and (c) a carboxyl group-containing product obtained by reacting a compound having a carboxyl group and two or more active hydrogens. A carboxyl obtained by neutralizing an isocyanate group-terminated prepolymer and emulsifying and dispersing it in water by self-emulsification, and then (d) chain-extending reaction using a polyamine compound having two or more amino groups and / or imino groups A group-containing polyurethane resin can be suitably used.

  There is no restriction | limiting in particular as such (a) organic diisocyanate, The aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate which have two isocyanate groups can be used. Examples of such (a) organic diisocyanate include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, norbornane diisocyanate, and 1,3-bis ( Examples thereof include alicyclic diisocyanate compounds such as isocyanatomethyl) cyclohexane, aromatic diisocyanate compounds such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. These diisocyanate compounds can be used individually by 1 type, or can also be used in combination of 2 or more type. Among such (a) organic diisocyanates, aliphatic diisocyanates and alicyclic diisocyanate compounds can be suitably used because they impart non-yellowing properties to the polishing sheet. In particular, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexyl. Methane diisocyanate, norbornane diisocyanate, and 1,3-bis (isocyanatomethyl) cyclohexane can be suitably used.

  The (b) polyol is not particularly limited as long as it has two or more hydroxyl groups, and is a polyether ester having an ether bond and an ester bond in addition to a polyester polyol, a polycarbonate polyol, a polyether polyol, and the like. Polyols can also be used.

  Examples of such polyester polyols include polyethylene adipate, polybutylene adipate, polyethylene butylene adipate, polyhexamethylene isophthalate adipate, polyethylene succinate, polybutylene succinate, polyethylene sebacate, polybutylene sebacate, poly-ε- Caprolactone diol, poly (3-methyl-1,5-pentylene) adipate, polycondensate of 1,6-hexanediol and dimer acid, polycondensate of nonanediol and dimer acid, ethylene glycol, adipic acid and dimer acid Examples thereof include copolycondensation.

  Examples of the polycarbonate polyol include polytetramethylene carbonate diol, polyhexamethylene carbonate diol, poly-1,4-cyclohexanedimethylene carbonate diol, and 1,6-hexanediol polycarbonate polyol.

  Furthermore, as the polyether polyol, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol homopolymer, block copolymer, random copolymer, ethylene oxide and propylene oxide, ethylene oxide and butylene oxide random copolymer And a block copolymer.

  Moreover, such (b) polyol can be used individually by 1 type, or can also be used in combination of 2 or more type. Furthermore, as an average molecular weight of such (b) polyol, it is preferable that it is 500-5000, and it is more preferable that it is 1000-3000. Moreover, as such (b) polyol, it is preferable to use polyester polyol or polycarbonate polyol from a viewpoint that moderate hardness can be provided to a polishing sheet with the carboxyl group-containing polyurethane resin obtained.

  Examples of the compound (c) having a carboxyl group and two or more active hydrogens include 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid. Furthermore, the compound having such a carboxyl group and two or more active hydrogens has a pendant carboxyl group obtained by reacting a diol having a carboxyl group with an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid. Polyester polyol can also be used. In place of the diol having a carboxyl group, a diol having no carboxyl group may be mixed and reacted as a diol component. Moreover, the compound which has such a carboxyl group and two or more active hydrogens can be used individually by 1 type, or can also be used in combination of 2 or more type.

  In addition, when producing an isocyanate group-terminated prepolymer by reacting (a) an organic diisocyanate, (b) a polyol, and (c) a compound having a carboxyl group and two or more active hydrogens, 2 is added as necessary. Low molecular weight chain extenders having more than one active hydrogen atom can be used.

  As such a low molecular weight chain extender having two or more active hydrogen atoms, the molecular weight is preferably 400 or less, and particularly preferably 300 or less. Such low molecular weight chain extenders include, for example, low molecular weight high molecular weights such as ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, sorbitol and the like. Examples thereof include low-molecular weight polyamines such as ethylene diamine, propylene diamine, hexamethylene diamine, diaminocyclohexyl methane, piperazine, 2-methyl piperazine, isophorone diamine, diethylene triamine, and triethylene tetramine. These low molecular weight chain extenders having two or more active hydrogen atoms can be used alone or in combination of two or more.

  In the present invention, the specific method for producing the carboxyl group-containing isocyanate group-terminated prepolymer is not particularly limited. For example, it is produced by a conventionally known one-stage so-called one-shot method, multi-stage isocyanate polyaddition reaction method or the like. can do. The reaction temperature at this time is preferably 40 to 150 ° C. In the reaction, a reaction catalyst such as dibutyltin dilaurate, stannous octoate, dibutyltin-2-ethylhexanoate, triethylamine, triethylenediamine, or N-methylmorpholine can be added as necessary. Moreover, the organic solvent which does not react with an isocyanate group can be added during reaction or after completion | finish of reaction. As such an organic solvent, for example, acetone, methyl ethyl ketone, toluene, tetrahydrofuran, dioxane, dimethylformamide, N-methylpyrrolidone and the like can be used.

  Moreover, in this invention, as a method of neutralizing a carboxyl group-containing isocyanate group terminal prepolymer, it can carry out using an appropriate method before preparation of a carboxyl group-containing isocyanate group terminal prepolymer, or after adjustment. There are no particular limitations on the compound used for neutralization of such carboxyl group-containing isocyanate group-terminated prepolymers, such as trimethylamine, triethylamine, tri-n-propylamine, tributylamine, N-methyl-diethanolamine, N, N-dimethyl. Mention may be made of amines such as monoethanolamine, N, N-diethylmonoethanolamine, triethanolamine, potassium hydroxide, sodium hydroxide, ammonia and the like. Among these, tertiary amines having no hydroxyl group such as trimethylamine, triethylamine, tri-n-propylamine, and tributylamine are particularly preferable.

  In the present invention, there are no particular limitations on the emulsifying equipment used when the neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer is emulsified and dispersed in water, and examples thereof include a homomixer, a homogenizer, and a disper. In addition, when emulsifying and dispersing, the neutralized product of carboxyl group-containing isocyanate group-terminated prepolymer is emulsified and dispersed in water at a temperature range of room temperature to 40 ° C. without using an emulsifier. It is preferable to suppress the reaction as much as possible. Furthermore, reaction inhibitors such as phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, p-toluenesulfonic acid, adipic acid, and benzoyl chloride can be added as necessary.

  Furthermore, in the present invention, a neutralized product of carboxyl group-containing isocyanate group-terminated prepolymer is emulsified and dispersed in water, and then (d) a chain extension reaction using a polyamine compound having two or more amino groups and / or imino groups. By doing so, an emulsified dispersion of the target (A) carboxyl group-containing polyurethane resin can be obtained.

  Examples of such (d) polyamine compounds having two or more amino groups and / or imino groups include ethylenediamine, propylenediamine, tetramethylenediamine, hexamethylenediamine, diaminocyclohexylmethane, piperazine, 2-methylpiperazine, and isophorone. Diamines such as diamine, norbornanediamine, diaminodiphenylmethane, tolylenediamine, xylylenediamine; polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, tris (2-aminoethyl) amine; Amidoamines derived from primary amines and monocarboxylic acids; water-soluble amine derivatives such as di-primary amine monoketimines; oxalic acid dihydrazide, malonic acid dihydrazide, oxalic acid diacid Dolazide, glutaric dihydrazide, adipic dihydrazide, sebacic acid dihydrazide, maleic dihydrazide, fumaric dihydrazide, itaconic dihydrazide, 1,1'-ethylenehydrazine, 1,1'-trimethylenehydrazine, 1,1 '-(1 , 4-butylene) dihydrazine and the like. These polyamine compounds having two or more amino groups and / or imino groups can be used singly or in combination of two or more.

  In the present invention, the chain elongation reaction of the neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer is carried out by adding (d) an amino group and an emulsion dispersion of the neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer described above. It can be carried out by adding a polyamine compound having two or more imino groups. Further, (d) an emulsified dispersion of a neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer can be added to a polyamine compound having two or more amino groups and / or imino groups. The chain extension reaction is preferably performed at a reaction temperature of 20 to 40 ° C., and is usually completed in 30 to 120 minutes. In addition, when an organic solvent is used when producing a carboxyl group-containing isocyanate group-terminated prepolymer, it is preferable to remove the organic solvent by, for example, vacuum distillation after the chain extension reaction is completed.

  In the present invention, the value of 100% modulus of the (A) carboxyl group-containing polyurethane resin is preferably 10 to 25 MPa, and more preferably 12 to 20 MPa. When the value of the 100% modulus is less than 10 MPa, the durability as a polishing sheet tends to be weak. On the other hand, when the value exceeds 25 MPa, the polishing sheet becomes hard, so that it is wound in the manufacturing process of the polishing sheet. There is a tendency that problems such as inability to occur. The value of 100% modulus is measured according to JIS K 6251 (1993), and when the distance between marked lines is increased by 100% using a dumbbell-shaped No. 3 test piece (when it is doubled). ) Is a value of a predetermined elongation tensile stress (MPa).

  Moreover, in this invention, it is preferable that it is 0.5-4.0 mass% as content of the carboxyl group in (A) carboxyl group-containing polyurethane resin, and is 1.0-2.0 mass%. It is more preferable. When the carboxyl group content is less than 0.5% by mass, the storage stability of the obtained (A) carboxyl group-containing polyurethane resin tends to deteriorate, while when it exceeds 4.0% by mass, (B) The thermal coagulation temperature generated when mixed with an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is increased, and the effect of preventing migration tends to be weakened during the production of the abrasive sheet.

  Furthermore, in the present invention, (A) the carboxyl group-containing polyurethane resin is preferably retained in the form of an emulsion dispersion, and the pH value is preferably 7.0 to 9.0, and 7.5 to 8 .5 is more preferable. When the pH value is less than 7.0, the storage stability of the emulsified dispersion of the (A) carboxyl group-containing polyurethane resin tends to be poor. On the other hand, when the pH value exceeds 9.0, migration occurs during the production of the abrasive sheet. The prevention effect tends to be weak.

  The (B) ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is not particularly limited as long as it is an ammonium salt using a carboxylic acid having 1 to 4 carbon atoms, and is commercially available. You can also use what you have. Examples of the carboxylic acid having 1 to 4 carbon atoms include carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, maleic acid, acrylic acid, and isocrotonic acid. Among such carboxylic acids having 1 to 4 carbon atoms, the impregnation property of the mixed solution, the migration preventing property of the carboxyl group-containing polyurethane resin in the drying step, and the volatilization during the drying are less likely to remain on the polishing sheet. For these reasons, formic acid or acetic acid can be preferably used.

  In the method for producing a polishing sheet of the present invention, when (B) an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is mixed with an emulsified dispersion of (A) a carboxyl group-containing polyurethane resin, (B) It is possible to mix the ammonium salt of carboxylic acid 1 to 4 in a solid (powder) state with an emulsified dispersion of (A) carboxyl group-containing polyurethane resin. From the viewpoint of maintaining the stability of the emulsified dispersion, it is preferable to mix (B) an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms in the form of an aqueous solution.

  In such an aqueous solution of (B) an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms, the concentration of the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is preferably 1 to 50% by mass. -30 mass% is more preferable. In the case of an aqueous solution in which the concentration of the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is less than 1% by mass, a large amount of the aqueous solution is used for (A) the carboxyl group-containing polyurethane resin in order to exhibit migration prevention properties during drying. It is necessary to add to the emulsified dispersion, and accordingly, the concentration of the (A) carboxyl group-containing polyurethane resin in the mixed solution is lowered. Therefore, since it is necessary to impregnate a large amount of the mixed liquid in order to fix the required amount of the carboxyl group-containing polyurethane resin to the nonwoven fabric, the amount of water volatilized during drying increases and the drying time becomes longer. There is a tendency for the economy to deteriorate. On the other hand, when the concentration of the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms exceeds 50% by mass, a precipitate is generated when mixed with the emulsion dispersion of (A) carboxyl group-containing polyurethane resin. It tends to impair stability.

  Moreover, as pH value of the ammonium salt aqueous solution of (B) C1-C4 carboxylic acid, it is preferable that it is 7.0-9.0, and it is more preferable that it is 7.5-8.5. . When the pH value is less than 7.0, precipitation tends to occur when mixing with the emulsion dispersion of (A) carboxyl group-containing polyurethane resin. On the other hand, when the pH value exceeds 9.0, migration occurs in the drying process. The prevention effect tends to be weak.

  In addition, (C) water according to the present invention has a role as a solvent when mixing (A) a carboxyl group-containing polyurethane resin and (B) an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms. Yes, ion-exchanged water or distilled water can be preferably used.

  In the present invention, the method for preparing a mixed solution containing (A) a carboxyl group-containing polyurethane resin, (B) an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms, and (C) water is not particularly limited, and is appropriately known. This method can be used.

  Moreover, in the said liquid mixture, as a compounding ratio of (A) carboxyl group-containing polyurethane resin and (B) ammonium salt of carboxylic acid having 1 to 4 carbon atoms, (A) :( B ) = 100: 0.5 to 100: 20, and more preferably 100: 2 to 100: 10. (A) When the compounding ratio of the carboxyl group-containing polyurethane resin and (B) the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms exceeds 100: 0.5, that is, the carboxylic acid having 1 to 4 carbon atoms. When the ammonium salt is less than 0.5, the migration preventing effect tends to be weak in the drying step, while when it is less than 100: 20, that is, when the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is 20 If it is more, the mixed solution tends to gel in the summer temperature atmosphere.

  Moreover, as a pH value of the said liquid mixture, it is preferable that it is 7.0-9.0, and it is more preferable that it is 7.5-8.5. When the pH value of the mixed solution is less than 7.0, the stability of the mixed solution tends to deteriorate. On the other hand, when the pH value exceeds 9.0, the migration preventing effect tends to be weakened in the drying process. is there.

  Furthermore, the thermal coagulation temperature of the mixed solution is preferably 35 to 60 ° C, more preferably 40 to 60 ° C. Here, the thermal coagulation temperature means that 50 g of the above mixed solution is put into a 100 mL glass beaker, the contents are stirred, the beaker is immersed in a constant temperature water bath of 95 ° C., and the contents are gradually heated. This is the temperature at which the solidification is lost. When the thermal coagulation temperature is less than 35 ° C., the mixed solution tends to gel in the summer temperature atmosphere. On the other hand, when it exceeds 60 ° C., the thermal coagulation does not appear sharply. In the drying process, the migration prevention property tends to be weakened.

  Moreover, as content of (A) carboxyl group-containing polyurethane resin in the said liquid mixture, it is preferable that it is 15-35 mass%, and it is more preferable that it is 20-30 mass%. When the content of the carboxyl group-containing polyurethane resin in the mixed solution is less than 15% by mass, a large amount of the mixed solution is impregnated into the nonwoven fabric in order to fix the necessary amount of the polyurethane resin. Since the amount of water volatilized by drying increases and the drying time becomes longer, the economy tends to deteriorate. On the other hand, when the content of the carboxyl group-containing polyurethane resin in the mixed solution exceeds 35% by mass, the stability of the mixed solution tends to deteriorate.

  Furthermore, although it does not specifically limit as a nonwoven fabric concerning this invention, For example, the entangled nonwoven fabric manufactured by the needle punch method, the hydroentanglement method, etc. can be used. Among such nonwoven fabrics, the entangled nonwoven fabric produced by the needle punch method can bring the fibers apart from each other to some extent, so that when the polyurethane resin is solidified and fixed, an appropriate gap is generated in the polishing sheet. Therefore, it can be suitably used because clogging is difficult.

  Among such non-woven fabrics, it is preferable to use a non-woven fabric composed of fibers having a titanium oxide content of 0.1% by mass or less (more preferably 0.08% by mass or less). When the amount of titanium oxide exceeds 0.1% by mass, the resulting polishing sheet contains a large amount of metal elements, and a large amount of the metal elements contained in the polishing sheet is easily taken into the object to be polished such as a silicon wafer. As a result, there is a tendency that the possibility of adversely affecting the electrical characteristics tends to increase. In addition, since it is common to add a large amount (about 0.3-3 mass%) of titanium oxide as an additive for controlling the glossiness of the polyester fiber, the amount of titanium oxide is 0.1 mass. % Polyester fiber is very special. Further, the amount of titanium oxide means a value measured by pre-processing by a wet decomposition method using an ICP (plasma emission spectral analyzer) based on EN 1122: 2001.

  The fibers constituting the nonwoven fabric are not particularly limited, and may include fibers produced using one or more of polyester fiber, nylon fiber, vinylon fiber, etc., and swell with polishing liquid. Polyester fibers are particularly preferred from the viewpoint that there is no ink.

Further, the fineness of the individual fibers constituting the non-woven fabric is not particularly limited, but when polishing using a polishing sheet obtained by increasing the flexibility of the fibers, the area of granulation becomes softer. The fineness is preferably 6.6 dtex or less, and more preferably 5.5 dtex or less, from the viewpoint that the polished surface of the work is less likely to be scratched. The lower limit of the fineness is not particularly limited, but 1.1 dtex is appropriate. For the same reason, the average fineness of the entire fibers constituting the nonwoven fabric is preferably 5.5 dtex or less, and more preferably 4.4 dtex or less. In addition, as a minimum of the average fineness of the whole fiber which comprises the said nonwoven fabric, it is preferable that it is 1.7 dtex or more. Further, the “fineness” mentioned here means a value obtained by the method A defined in JIS L 1015 (1999), and the “average fineness” is a cross section in the thickness direction of the nonwoven fabric with a scanning electron microscope. Photographed at double magnification, extracted 100 arbitrary fibers representing a fiber cross section cut at right angles to the length direction of the fibers, measured individual diameters with calipers, and calculated 100 arithmetic average fibers After calculating the diameter, it refers to a value converted to fineness (weight per 1000 m (g)) based on the fiber density.

Further, the fiber length of the fibers constituting the nonwoven fabric is not particularly limited, but the fiber length is preferably 20 to 100 mm from the viewpoint of easily obtaining the bonding strength between the fibers, and 30 More preferably, it is ˜80 mm. Here, the “fiber length” refers to the length of the fiber obtained by JIS L 1015 (1999) (chemical fiber staple test method) B method (corrected staple diagram method).

Further, as the basis weight of the nonwoven fabric is preferably 100 to 400 g / ^{m 2,} and more preferably 200-30Og / ^{m 2.} When the basis weight exceeds 400 g / m ² , it becomes easy to obtain a polishing sheet having a dense structure, and the polishing sheet tends to be clogged quickly. On the other hand, when the basis weight is lower than 100 g / m ² , polishing is obtained. In addition to the fact that the thickness of the polishing sheet is reduced and the workability to attach to the polishing machine is reduced, the amount of work to be polished per polishing sheet tends to be reduced. The “weight per unit” here refers to the value defined in 8.4.2 “Mass per unit area in standard state of woven fabric” of JIS L 1096 (1999) “General woven fabric testing method”.

The thickness of the nonwoven fabric is preferably 0.8 to 2 mm (20 gf / cm at ² load), and more preferably 1～1.8Mm. When the thickness is thicker than 2 mm, the thickness tends to change greatly between the initial use stage and the final use stage of the polishing sheet, and when thinner than 0.8 mm, the workability of attaching to the polishing machine is lowered and polishing is performed. There is a tendency that the processing amount of the object to be polished per sheet is reduced.

  In the method for producing a polishing sheet of the present invention, the present invention includes (A) a carboxyl group-containing polyurethane resin, (B) a carboxylic acid ammonium salt having 1 to 4 carbon atoms, and (C) a mixed solution containing water. Various additives can be used in combination in order to impart processability within a range not impairing the purpose of the above. For example, various penetrants such as lower alcohols, glycol-based solvents, alcohol-based nonionic surfactants, acetylene glycol-based nonionic surfactants, silicone-based surfactants, fluorine-based surfactants; antioxidants , Various stabilizers such as light resistance improvers and UV inhibitors; various antifoaming agents such as mineral oils and silicones; adding urethanizing catalysts, colorants such as plasticizers and pigments, pot life extenders, etc. These can be used alone or in combination of two or more.

  Among such additives, it is particularly preferable to use a penetrant. By using a penetrant, the nonwoven fabric can be quickly impregnated with the mixed solution, and an effect of uniformly fixing a polyurethane resin to the nonwoven fabric can be obtained. Such penetrants are not particularly limited as long as they are generally used, but lower alcohols and glycol solvents are particularly preferable because they are highly volatile during drying and do not remain.

  Further, in the production method of the present invention, the method for impregnating the non-woven fabric with the mixed solution is not particularly limited. For example, a conventionally known method such as impregnation processing or spraying treatment using a dip-nip method is preferably employed. In addition, the concentration and processing conditions of the mixed solution can be appropriately selected.

  In the production method of the present invention, the method for drying the impregnated nonwoven fabric after impregnating the mixed solution is not particularly limited. For example, dry drying using hot air; ) And high pressure steamer (HPSS); microwave irradiation drying and the like can be used, and dry drying using hot air can be suitably used in terms of continuous processability. . Such a drying method can be used individually by 1 type, or can also be used in combination of 2 or more type. When dry drying using the hot air is used, the processing temperature is preferably 60 to 190 ° C., the processing time is preferably 1 to 20 minutes, the processing temperature is 100 to 170 ° C., and the processing time is 2 More preferably, it is set to -5 minutes.

  In this way, (A) a carboxyl group-containing polyurethane resin, (B) a mixed solution containing an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms and (C) water is impregnated into a nonwoven fabric and then dried. The polishing sheet of the present invention can be obtained.

  In such a polishing sheet of the present invention, the amount of fixed solids such as polyurethane resin in the polishing sheet is not particularly limited, but the component derived from the (A) carboxyl group-containing polyurethane resin is contained in the polishing sheet. It is preferable that the component derived from 30-80 mass% and (B) ammonium salt of carboxylic acid whose carbon number is 1-4 is about 2-7 mass%.

  The polishing sheet obtained by the present invention is a field where high surface flatness such as optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, resin plates for information recording and ceramic plates is required, It can be used as a polishing sheet and / or a polishing pad.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

  In addition, the sheet | seat for polishing obtained by the Example and the comparative example was evaluated with the following evaluation method.

(1) Migration prevention property Using a scanning electron microscope [manufactured by JEOL Ltd., JSM5600LV], the cross section of the polishing sheet was observed at a magnification of 60 times, and the fixed state of the polyurethane resin present in the center of the nonwoven fabric was The fixed state of the polyurethane resin present on the surface of the nonwoven fabric was compared and evaluated according to the following criteria.
Grade 5: In the polishing sheet cross section, there is no difference in the resin fixing amount between the central portion and the surface portion, and no migration occurs.
Fourth grade: In the cross section of the polishing sheet, there is almost no difference in the resin fixing amount between the central portion and the surface portion, and no migration occurs.
Third grade: In the cross section of the polishing sheet, a slight difference is observed in the resin fixing amount between the central portion and the surface portion, and no resin fixing is observed in 10% of the central portion in the entire thickness.
Second grade: In the cross section of the polishing sheet, there is a considerable difference in the resin fixing amount between the central portion and the surface portion, and no resin fixing is observed in 30% of the central portion in the total thickness.
First grade: In the cross section of the polishing sheet, there is a marked difference in the resin fixing amount between the central portion and the surface portion, and no resin fixing is observed in 50% of the central portion in the total thickness.

(2) Abrasion test According to the Taber method of JIS L 1096 (1999), a Taber abrasion tester [manufactured by Yasuda Seiki Seisakusho, NO. 101], using a hard wheel H-22 and applying a load of 500 g to wear the abrasive sheet 3000 times, measure the thickness (Tr) of the worn portion of the abrasive sheet with a micrometer, Compared with the measured thickness (Tn) of the non-wear portion, the degree of grinding (Sd, unit:%) was calculated by the following formula and evaluated according to the following criteria.
Formula: Sd = [1- (Tr / Tn)] × 100
Grade 5: Grinding degree is 10% or less.
Grade 4: Grinding degree exceeds 10% and is 20% or less.
Third grade: Grinding degree exceeds 20% and is 30% or less.
Second grade: Grinding degree exceeds 30% and is 40% or less.
First grade: Grinding degree exceeds 40%.

(3) Hardness test In accordance with the hardness test method of JIS K 6253 (1993), the hardness of the five polishing sheets stacked by a durometer hardness tester [manufactured by Tecrock Co., Ltd., Shore A (Penetration method)] It was measured.

(4) Morphological stability test Using a compression recovery rate measuring device [manufactured by Tester Sangyo Co., Ltd.] according to the compression rate and recovery rate measurement method of JIS R 3453 (1995), the polishing sheet was previously kept at a constant temperature of 50 ° C The sample was allowed to stand inside and subjected to an aging treatment, and then stacked to form a sample. Then, the sample is compressed and restored according to a condition cycle of an initial load of 1.75 kg / cm ² , a total load of 70 kg / cm ² and an initial load of 1.75 kg / cm ² , and the thickness of the sample in each load state Was measured, and a restoration rate (Rr, unit:%) was calculated by the following formula, and evaluated according to the following criteria.
Formula: Rr = [(RM) / (PM)] × 100
(In the formula, P indicates the thickness when the initial initial load (1.75 kg / cm ² ) is applied, M indicates the thickness when the total load (70 kg / cm ² ) is applied, and R Indicates the thickness when the initial load (1.75 kg / cm ² ) is restored.)
Grade 5: Restoration rate is 50% or more.
Fourth grade: Restoration rate is 40% or more and less than 50%.
Third grade: The restoration rate is 30% or more and less than 40%.
Second grade: The restoration rate is 20% or more and less than 30%.
First grade: Restoration rate is less than 20%.

[Synthesis Examples 1 to 3 and Comparative Synthesis Example 1]
Below, the synthesis example of the carboxyl group-containing polyurethane resin used for this invention and the comparative synthesis example of the water-based polyurethane resin used for a comparative example are shown.

(Synthesis Example 1)
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 146.8 g of 1,6-hexanediol polycarbonate polyol (average molecular weight 2000), 6.3 g of 1,4-butanediol, dimethylol Charge 10.0 g of propionic acid, 0.001 g of dibutyltin dilaurate and 105 g of methyl ethyl ketone, mix uniformly, add 81.8 g of dicyclohexylmethane diisocyanate, react at 420C for 420 minutes, and content of free isocyanate groups relative to non-volatile content Of 2.25 mass% of a methyl ethyl ketone solution of a carboxyl group-containing isocyanate group-terminated prepolymer.

  After cooling the solution to 50 ° C. or lower, 7.2 g of triethylamine was added and a neutralization reaction was performed at 40 ° C. for 30 minutes. Next, the neutralized solution is cooled to 30 ° C. or lower, and 412.0 g of water is gradually added using a disperse blade to emulsify and disperse the neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer. Got. Then, an aqueous polyamine solution in which 14.5 g of piperazine hexahydrate and 1.3 g of diethylenetriamine are dissolved in 20 g of water is added to the dispersion and subjected to a chain extension reaction for 90 minutes, followed by removal at 35 ° C. under reduced pressure. Water of a stable carboxyl group-containing polyurethane resin having a non-volatile content of 35.0% by mass, a viscosity of 70.0 mPa · s (BM viscometer, No. 1 rotor, 60 rpm), a pH value of 7.8, and an average particle size of 100 nm. A dispersion was obtained.

  The carboxyl group content in this carboxyl group-containing polyurethane resin was 1.4% by mass, and the 100% modulus was 18 MPa. Further, the aqueous dispersion of the carboxyl group-containing polyurethane resin did not gel when heated at 90 ° C., and had no heat-sensitive coagulation property.

(Synthesis Example 2)
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 87.8 g of 1,6-hexanediol polycarbonate polyol (average molecular weight 1000), 32.8 g of dimethylolpropionic acid, dibutyltin dilaurate 0 .001 g and methyl ethyl ketone 105 g were charged and mixed uniformly, and then 124.4 g of dicyclohexylmethane diisocyanate was added and reacted at 80 ° C. for 300 minutes. The content of free isocyanate groups relative to the nonvolatile content was 3.42% by mass. A methyl ethyl ketone solution of the isocyanate group-terminated prepolymer was obtained.

  After cooling the solution to 50 ° C. or lower, 23.5 g of triethylamine was added and a neutralization reaction was performed at 40 ° C. for 30 minutes. Next, the neutralized solution is cooled to 30 ° C. or lower, and 400.0 g of water is gradually added using a disperse blade to emulsify and disperse the neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer. Got. Then, an aqueous polyamine solution prepared by dissolving 9.5 g of 60% by mass hydrated hydrazine and 2.0 g of diethylenetriamine in 20 g of water was added to the dispersion and subjected to a chain extension reaction for 90 minutes, and then at 35 ° C. under reduced pressure. Solvent removal, a stable carboxyl group-containing polyurethane resin having a non-volatile content of 35.0% by mass, a viscosity of 150.0 mPa · s (BM viscometer, No. 1 rotor, 60 rpm), a pH value of 8.1 and an average particle size of 50 nm An aqueous dispersion was obtained.

  The carboxyl group-containing polyurethane resin contained in this carboxyl group-containing polyurethane resin was 4.5% by mass, and the 100% modulus was 20 MPa. Further, the aqueous dispersion of the carboxyl group-containing polyurethane resin did not gel when heated at 90 ° C., and had no heat-sensitive coagulation property.

(Synthesis Example 3)
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 146.8 g of 1,6-hexanediol polycarbonate polyol (average molecular weight 2000), 6.3 g of 1,4-butanediol, dimethylol Charge 10.0 g of propionic acid, 0.001 g of dibutyltin dilaurate and 105 g of methyl ethyl ketone, mix uniformly, add 81.8 g of dicyclohexylmethane diisocyanate, react at 420C for 420 minutes, and content of free isocyanate groups relative to non-volatile content Of 2.25 mass% of a methyl ethyl ketone solution of a carboxyl group-containing isocyanate group-terminated prepolymer.

  After cooling the solution to 50 ° C. or lower, 9.1 g of triethylamine was added and a neutralization reaction was performed at 40 ° C. for 30 minutes. Next, the neutralized solution is cooled to 30 ° C. or lower, and 410.1 g of water is gradually added using a disper blade to emulsify and disperse the neutralized product of the carboxyl group-containing isocyanate group-terminated prepolymer. Got. Then, 14.5 g of piperazine hexahydrate and a polyamine aqueous solution obtained by dissolving 1.3 g of diethylenetriamine in 20 g of water are added to the dispersion, and after 90 minutes of chain extension reaction, the solvent is removed at 35 ° C. under reduced pressure. Water dispersion of a stable carboxyl group-containing polyurethane resin having a nonvolatile content of 35.0 mass%, a viscosity of 90.0 mPa · s (BM viscometer, No. 1 rotor, 60 rpm), a pH value of 9.5, and an average particle diameter of 70 nm. I got a thing.

  The carboxyl group content in this carboxyl group-containing polyurethane resin was 1.4% by mass, and the 100% modulus was 18 MPa. Further, the aqueous dispersion of the carboxyl group-containing polyurethane resin did not gel when heated at 90 ° C., and had no heat-sensitive coagulation property.

(Comparative Synthesis Example 1)
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 76.1 g of 1,6-hexanediol polycarbonate polyol (average molecular weight 1000), polyoxyethylene polypropylene random copolymer glycol (average molecular weight) 1000, 70 mass% containing oxyethylene group) 16.9 g, 1.5 g of 1,4-butanediol, 1.9 g of trimethylolpropane, 0.001 g of dibutyltin dilaurate and 60 g of methyl ethyl ketone, and after mixing uniformly, dicyclohexyl 40.4 g of methane diisocyanate was added and reacted at 80 ° C. for 300 minutes to obtain a methyl ethyl ketone solution of an isocyanate group-terminated prepolymer having a free isocyanate group content of 2.10% by mass relative to the nonvolatile content.

  After cooling the solution to 30 ° C. or lower, 0.1 g of decyl phosphate ester and 6.0 g of polyoxyethylene tristyryl phenyl ether (HLB = 15) were added and mixed uniformly, and then water 254 was added using a disper blade. 0.0 g was gradually added to perform phase inversion emulsification and dispersion to obtain a dispersion. Then, 2.0 g of piperazine hexahydrate and an aqueous polyamine solution in which 0.8 g of diethylenetriamine is dissolved in 11.3 g of water are added to the dispersion, and after 90 minutes of chain extension reaction, at 35 ° C. under reduced pressure. Solvent removal, water dispersion of a stable aqueous polyurethane resin having a non-volatile content of 35.0 mass%, a viscosity of 50.0 mPa · s (BM viscometer, No. 1 rotor, 60 rpm), a pH value of 8.2 and an average particle size of 520 nm I got a thing.

  The carboxyl group content in this aqueous polyurethane resin was 0.0% by mass, and the 100% modulus was 4 MPa. The aqueous dispersion of the aqueous polyurethane resin was gelled at 45 ° C. and had heat-sensitive coagulation properties.

  The properties of Synthesis Examples 1 to 3 and Comparative Synthesis Example 1 are summarized in Table 1 below.

[Nonwoven fabric]
Only a polyester fiber having a titanium oxide content of 0.07% by mass (fineness: 3.3 dtex, fiber length: 64 mm, manufactured by Teijin Ltd., trade name: Teijin Tetron TA04B) is opened by a card machine to form a fiber web. After that, needle punching was performed at a needle density of 1000 / cm ² to produce a polyester entangled nonwoven fabric (weight per unit: 265 g / m ² , thickness: 1.65 mm, average fineness: 3.3 dtex).

[Examples 1 to 4 and Comparative Example 5]
Example 1
100 g of an aqueous dispersion of the carboxyl group-containing polyurethane resin obtained in Synthesis Example 1, 17.5 g of a 10% by weight aqueous solution of ammonia acetate (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nikka Chemical A mixed solution was prepared by uniformly mixing 6.0 g of a 50% by mass aqueous solution and 16.5 g of water. The mixture ratio of the carboxyl group-containing polyurethane resin and ammonia acetate in the mixed solution was 100: 5, the pH value was 7.9, the thermal coagulation temperature was 45 ° C., and the amount of the carboxyl group-containing polyurethane resin was 25% by mass.

The mixed solution is impregnated into a polyester entangled nonwoven fabric using a slit mangle so as to be 300% by mass of pickup, and then dried in a hot air dryer at a temperature of 150 ° C. for 3 minutes to solidify the polyurethane resin. Thus, a fixed polyurethane non-woven fabric (weight per unit: 480 g / m ² , thickness: 1.45 mm) was obtained. Next, buffing treatment was performed on both surfaces of the polyurethane-fixed nonwoven fabric to obtain a polishing sheet (weight per unit: 400 g / m ² , thickness: 1.2 mm).

(Example 2)
100 g of an aqueous dispersion of the carboxyl group-containing polyurethane resin obtained in Synthesis Example 1, 26.3 g of a 20% by weight aqueous solution of ammonia acetate (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nikka Chemical 6.0 g of 50% by mass aqueous solution and 7.7 g of water were uniformly mixed to prepare a mixed solution. The mixture ratio of the carboxyl group-containing polyurethane resin and ammonia acetate in the mixed solution was 100: 15, the pH value was 7.6, the thermal coagulation temperature was 45 ° C., and the carboxyl group-containing polyurethane resin amount was 25% by mass.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

(Example 3)
100 g of an aqueous dispersion of a carboxyl group-containing polyurethane resin obtained in Synthesis Example 2, 17.5 g of a 10% by mass aqueous solution of ammonia acetate (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nika Chemical A mixed solution was prepared by uniformly mixing 6.0 g of a 50% by mass aqueous solution and 16.5 g of water. The mixed solution had a carboxyl group-containing polyurethane resin: ammonia acetate of 100: 5, a pH value of 8.0, a thermal coagulation temperature of 51 ° C., and a carboxyl group-containing polyurethane resin amount of 25% by mass.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

Example 4
100 g of an aqueous dispersion of a carboxyl group-containing polyurethane resin obtained in Synthesis Example 3, 17.5 g of a 10% by mass aqueous solution of ammonia acetate (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nika Chemical A mixed solution was prepared by uniformly mixing 6.0 g of a 50% by mass aqueous solution and 16.5 g of water. The mixture ratio of the carboxyl group-containing polyurethane resin and ammonia acetate in the mixed solution was 100: 5, the pH value was 9.2, the thermal coagulation temperature was 70 ° C., and the carboxyl group-containing polyurethane resin amount was 25% by mass.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

(Comparative Example 1)
100 g of an aqueous dispersion of carboxyl group-containing polyurethane resin obtained in Synthesis Example 1, 6.0 g of 50% by weight aqueous solution of Textport BG [alcohol penetrant, trade name, manufactured by Nikka Chemical Co., Ltd.] and 34.0 g of water Were mixed uniformly to prepare a mixed solution. The mixture ratio of the carboxyl group-containing polyurethane resin and ammonia acetate in the mixed solution is 100: 0, the pH value is 7.8, the thermal coagulation temperature is 90 ° C. or more, and the carboxyl group-containing polyurethane resin amount is 25% by mass. there were.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

(Comparative Example 2)
100 g of an aqueous dispersion of a carboxyl group-containing polyurethane resin obtained in Synthesis Example 1, 17.5 g of a 10% by weight aqueous solution of acetic acid (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nika Kagaku ( A mixed solution was prepared by uniformly mixing 6.0 g of a 50% by mass aqueous solution and 16.5 g of water. The mixture ratio of the carboxyl group-containing polyurethane resin and acetic acid in the mixed solution was 100: 5, the pH value was 7.9, the thermal coagulation temperature was 20 ° C. or less, and the carboxyl group-containing polyurethane resin amount was 25% by mass. It was.

  In addition, since the mixed liquid gelled instantly when the 10 mass% aqueous solution of acetic acid was added, the production of the polishing sheet was abandoned.

(Comparative Example 3)
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Comparative Synthesis Example 1, 6.0 g of 50 mass% aqueous solution of Textport BG [alcohol penetrant, trade name, manufactured by Nikka Chemical Co., Ltd.] and 34.0 g of water The liquid mixture was adjusted by mixing uniformly. The mixture ratio of the aqueous polyurethane resin and ammonia acetate in this mixed solution was 100: 0, the pH value was 8.2, the thermal coagulation temperature was 45 ° C., and the amount of the aqueous polyurethane resin was 25% by mass.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

(Comparative Example 4)
100 g of an aqueous dispersion of an aqueous polyurethane resin obtained in Comparative Synthesis Example 1, 17.5 g of a 10% by mass aqueous solution of ammonia acetate (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nikka Chemical ( A mixed solution was prepared by uniformly mixing 6.0 g of a 50% by mass aqueous solution and 16.5 g of water. The mixture ratio of the aqueous polyurethane resin and ammonia acetate in the mixed solution was 100: 5, the pH value was 7.9, the thermal coagulation temperature was 45 ° C., and the amount of the aqueous polyurethane resin was 25% by mass.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

(Comparative Example 5)
100 g of the aqueous dispersion of the aqueous polyurethane resin obtained in Comparative Synthesis Example 1, 17.5 g of a 10 mass% aqueous solution of calcium chloride (pH value 7.3), Textport BG [alcohol penetrant, trade name, Nikka Chemical ( A mixed solution was prepared by uniformly mixing 6.0 g of a 50% by mass aqueous solution and 16.5 g of water. The aqueous polyurethane resin and calcium chloride of this mixed solution were 100: 5, the pH value was 8.1, the thermal coagulation temperature was 35 ° C., and the amount of the aqueous polyurethane resin was 25% by mass.

  A polishing sheet was obtained in the same manner as in Example 1 except that such a mixed solution was used.

  The evaluation results of the polishing sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 5 are summarized in Table 2 below.

  In the polishing sheets obtained in Examples 1 to 4, no migration was observed, the resin was uniformly fixed to the inside of the nonwoven fabric, and it was confirmed that the abrasion resistance, hardness, and air permeability were excellent. . Moreover, since there were no residues, such as surfactant and inorganic salt, in the polishing sheet obtained in Examples 1-4, it was confirmed that it is excellent in quality as a polishing sheet.

  On the other hand, in the polishing sheet obtained in Comparative Example 1 using only the carboxyl group-containing polyurethane resin and not containing an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms, it was recognized that significant migration occurred during drying. The abrasion resistance as a polishing sheet was insufficient.

  In Comparative Example 2, an acetic acid aqueous solution was used in place of the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms. However, since the mixed solution was gelled, a polishing sheet could not be produced and the processability was poor. It was enough.

  Further, the polishing sheet obtained in Comparative Example 3 using only the heat-sensitive coagulable aqueous polyurethane resin obtained by emulsification with a surfactant without using an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms. However, the anti-migration property was insufficient and the abrasion resistance as an abrasive sheet was insufficient. Further, since the surfactant remains in the polishing sheet, the quality as the polishing sheet was insufficient.

  In addition, in the polishing sheet obtained in Comparative Example 4 using the aqueous polyurethane resin obtained by emulsification with a surfactant, the same result as in Comparative Example 3 was observed, and it had heat-sensitive coagulability. In addition, it was confirmed that the ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is ineffective for preventing migration of an aqueous polyurethane resin obtained by emulsification with a surfactant.

  Polishing obtained in Comparative Example 5 mixed with an aqueous polyurethane resin obtained by emulsification with a surfactant using an inorganic salt aqueous solution made of calcium chloride instead of an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms In the sheet, the thermal coagulation temperature is lowered by the inorganic salt aqueous solution, and the migration prevention property is slightly improved. However, when compared with the polishing sheets obtained in Examples 1 to 5, the migration prevention property is insufficient. It was confirmed that the abrasion resistance as a polishing sheet was insufficient. Further, since the surfactant and the inorganic salt remain in the polishing sheet obtained in Comparative Example 5, the quality as the polishing sheet was insufficient.

  As described above, according to the method for producing an abrasive sheet of the present invention, the resin can be uniformly fixed inside the nonwoven fabric, and the abrasion resistance and shape stability of the abrasive sheet required as an abrasive sheet. It is possible to obtain a polishing sheet excellent in the above.

  Further, according to the method for producing a polishing sheet of the present invention, it is possible to produce a polishing sheet using an aqueous polyurethane resin without using an organic solvent-based polyurethane resin. This makes it possible to reduce problems such as air pollution and water pollution caused by organic solvents discharged during processing, solvent recovery labor, workers' working environment, and the like.

  Furthermore, the polishing sheet obtained by the production method of the present invention does not contain impurities such as surfactants and inorganic salts, is excellent in quality as a polishing sheet, and imparts stable polishing properties to the object to be polished. Therefore, it can be used as it is in industrial fields such as optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and general metal polishing, and has high surface flatness. It becomes possible to provide the required planarization of the material stably and with high polishing efficiency.

Claims (10)

  (A) A carboxyl group-containing polyurethane resin, (B) a mixed solution containing a carboxylic acid ammonium salt having 1 to 4 carbon atoms and (C) water is impregnated into a nonwoven fabric and then dried to obtain a polishing sheet. A method for producing a polishing sheet, comprising:   In the mixed solution, the blending ratio of (A) carboxyl group-containing polyurethane resin and (B) ammonium salt of carboxylic acid having 1 to 4 carbon atoms is (A) :( B) = It is 100: 0.5-100: 20, The manufacturing method of the polishing sheet of Claim 1 characterized by the above-mentioned.   (A) Carboxyl group-containing isocyanate resin is obtained by reacting a carboxyl group-containing polyurethane resin with (a) an organic diisocyanate, (b) a polyol, and (c) a compound having a carboxyl group and two or more active hydrogens. A carboxyl group-containing polyurethane resin obtained by neutralizing a polymer and emulsifying and dispersing it in water by self-emulsification, and then (d) a chain extension reaction using a polyamine compound having two or more amino groups and / or imino groups. The method for producing a polishing sheet according to claim 1, wherein the method is a polishing sheet.   (A) The content of carboxyl groups in the carboxyl group-containing polyurethane resin is 0.5 to 4.0% by mass, for polishing according to any one of claims 1 to 3. Sheet manufacturing method.   (A) The value of 100% modulus of a carboxyl group-containing polyurethane resin is 10 to 25 MPa, The method for producing a polishing sheet according to any one of claims 1 to 4.   The method for producing a polishing sheet according to any one of claims 1 to 5, wherein the carboxylic acid having 1 to 4 carbon atoms is formic acid or acetic acid.   The pH value of the said liquid mixture is 7.0-9.0, and solidification temperature is 35-60 degreeC, The manufacture of the polishing sheet as described in any one of Claims 1-6 characterized by the above-mentioned. Method.   The method for producing a polishing sheet according to any one of claims 1 to 7, wherein the nonwoven fabric is a nonwoven fabric composed of fibers having a titanium oxide content of 0.1 mass% or less.   The method for producing a polishing sheet according to claim 8, wherein the fiber is a polyester fiber.   A polishing sheet obtained by the production method according to any one of claims 1 to 9.