JP2003171433A - Method for producing expanded polyurethane polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polishing pad which has a polishing layer of expanded polyurethane and stable polishing characteristics, and especially a method for producing a polishing pad which does not contains a material to form recessed parts on a polished face, for example, a water-soluble resin fine particle or hollow fine particle, polystyrene foam bead, etc., consequently, has holes composed of polyurethane alone. <P>SOLUTION: This method for producing a polishing pad of expanded polyurethane comprises a stirring process for adding a silicone-based surfactant to an isocyanate-terminated prepolymer and stirring the prepolymer in the presence of a nonreactive gas to give a bubble dispersion, a mixing process for adding a chain extender to the bubble dispersion to give a foam reaction solution, a curing process for reacting and curing the foam reaction solution. The isocyanate monomer content of the isocyanate-terminated prepolymer is ≤20 wt.%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials requiring high surface flatness such as general metal polishing. The present invention relates to a polishing pad capable of stably performing the flattening process of (1) with high polishing efficiency. The polishing pad of the present invention is particularly used in a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon before laminating and forming these oxide layer and metal layer. It is also possible to do so.

[0002]

2. Description of the Related Art A typical example of a material required to have a high degree of surface flatness is a semiconductor integrated circuit (IC, LSI).
There is a single crystal silicon disk called a silicon wafer used for manufacturing. Silicon wafer is IC, LS
In the manufacturing process such as I, in order to form a reliable semiconductor junction of various thin films used for circuit formation, it is required to finish the surface with high precision in each process. In such a polishing finishing process, a polishing pad is generally fixed to a rotatable support disk called a platen, and a workpiece such as a semiconductor wafer is fixed to a polishing head. A polishing operation is performed by generating a relative speed between the platen and the polishing head by the movements of both, and further continuously supplying the polishing slurry containing abrasive grains onto the polishing pad.

A polishing pad used for such CMP processing is disclosed in Japanese Patent No. 3013105 and Japanese Patent Laid-Open No.
The technique described in JP-A-1-322878 is known. The technique disclosed in Japanese Patent No. 3013105 is a polishing pad in which fine particles or hollow fine particles of a water-soluble resin are added to a polymer matrix such as a polyurethane polymer. The technique disclosed in JP-A No. 11-322878 is a polishing pad in which polystyrene foam beads are dispersed in polyurethane polymer.

[0004]

However, in the above-mentioned known polishing pad, when the fine particles or hollow fine particles of the water-soluble resin or the polystyrene foam beads are dispersed in the resin, the density of the fine particles of the matrix resin, that is, polyurethane, is increased. Is likely to cause non-uniformity of dispersed particles.
The fine particles or hollow fine particles in the above-mentioned known art are CM
In the P processing, a small recess is formed on the polishing surface of the polishing pad to exert an important function of holding the polishing abrasive grains, and the nonuniformity of the dispersed fine particles has a great influence on the performance of the polishing pad.

On the other hand, in the case of a foamed polyurethane polishing pad obtained by reacting and curing an isocyanate group-containing compound with a compound containing an active hydrogen group, sufficient polishing performance cannot be obtained even if the same components are used. Sometimes,
Improvement is required.

An object of the present invention is to provide a method of manufacturing a polishing pad having a polishing layer made of foamed polyurethane and having stable polishing characteristics. Further, the object of the present invention is not particularly to include a fine particle or hollow fine particle of a water-soluble resin, or a material such as polystyrene foam beads for forming a recess on the polishing surface, and therefore the polishing pad whose pores are composed of only polyurethane. It is to provide a method for manufacturing a polishing pad having

[0007]

The present inventors have found that when an isocyanate group-terminated prepolymer is used as an isocyanate group-containing compound which is a raw material for foamed polyurethane,
By controlling the content of the isocyanate monomer in the isocyanate group-terminated prepolymer to be not more than a predetermined value, the abrasion resistance during polishing is good, and it was found that a polishing pad excellent in polishing characteristics can be obtained. Completed the invention.

That is, the present invention is a method for producing a foamed polyurethane polishing pad, which comprises adding a silicone-based surfactant to an isocyanate-terminated prepolymer and stirring the mixture in the presence of a non-reactive gas to prepare a foam dispersion liquid. Step, a mixing step of adding a chain extender to the cell dispersion and mixing to form a foaming reaction solution, a curing step of reacting and curing the foaming reaction solution, the isocyanate monomer content of the isocyanate-terminated prepolymer is It is characterized by being 20% by weight or less.

It is not clear why the use of a prepolymer having an isocyanate monomer content of 20% by weight or less improves the polishing characteristics, but if the isocyanate monomer content exceeds 20%, the chain extender and the isocyanate monomer content will increase. It is presumed that one reason is that the reaction proceeds first and the high molecular weight of polyurethane does not sufficiently occur.

The foamed polyurethane obtained is one in which fine bubbles are formed without adding a material such as fine particles or hollow fine particles of a water-soluble resin or polystyrene foam beads for forming concave portions on the polishing surface. The presence of the fine bubbles enables the abrasive grains in the slurry to be retained on the pad surface during the polishing operation, so that a satisfactory polishing rate can be obtained. The fine bubbles in the polyurethane foam are
The average cell diameter is 70 μm or less, preferably 50 μm or less, and further 40 μm or less. Generally, it is preferably 30 to 40 μm.

In the above invention, the isocyanate-terminated prepolymer uses, as an isocyanate component, at least one kind of aliphatic diisocyanate and alicyclic diisocyanate (first isocyanate component) and aromatic diisocyanate (second isocyanate component). And the ratio in the isocyanate monomer is the first isocyanate component / second isocyanate component = 0.5 to
It is preferably 3.2 (weight ratio).

As a diisocyanate component constituting the isocyanate-terminated prepolymer, a relatively slow-reacting aliphatic diisocyanate or alicyclic diisocyanate is used in combination with an aromatic diisocyanate to obtain good polishing characteristics and to mix with a chain extender. The resulting polyurethane foam has an appropriate curing time and is easy to manufacture.

The first isocyanate component is 4,4'-
It is preferably dicyclohexylmethane diisocyanate, and the second isocyanate component is toluene diisocyanate.

By using such an isocyanate component,
It is possible to obtain a polyurethane foam that has excellent physical properties of the resin that constitutes the polyurethane foam and that has particularly good polishing properties.

When the weight ratio of the first isocyanate component / second isocyanate component in the isocyanate monomer in the isocyanate-terminated prepolymer is less than 0.5, the curing time is short and stable foamed polyurethane or polishing pad cannot be formed. . On the other hand, when the weight ratio of the first isocyanate component / the second isocyanate component exceeds 3.2, it takes time to complete the curing step of reacting and curing the isocyanate-terminated prepolymer and the chain extender, which leads to an increase in cost and is not preferable. .

In the method for producing a foamed polyurethane polishing pad of the present invention, the addition amount of the silicon-based surfactant in the stirring step is 0.05 to 5% by weight in polyurethane.
Is preferred.

In the production of polyurethane foam, it is advantageous to preliminarily mix a silicone-based surfactant with a polyurethane raw material in order to stably form fine bubbles, and the bubbles are uniform without impairing the physical properties of polyurethane. A stable polyurethane foam can be obtained.

The amount of the silicon-based surfactant added is 0.
If it is less than 05% by weight, a foam having fine cells may not be obtained. On the other hand, if the addition amount exceeds 5% by weight, the number of cells (cells) in the polyurethane foam increases, and it is difficult to obtain a polyurethane microcellular foam having high hardness. Further, due to the action of the silicone-based surfactant, which is presumed to be plasticization of polyurethane, the strength of the polishing pad is lowered and the polishing characteristics are lowered.

In the method of manufacturing the polishing pad described above,
It is preferable to have a laminating step of further laminating a flexible porous sheet on the polishing pad.

By providing the flexible porous sheet as the cushion layer, a polishing pad having more excellent flattening characteristics can be obtained.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The polyurethane constituting the polishing pad of the present invention comprises an organic polyisocyanate, a polyol compound and a chain extender.

As the organic polyisocyanate, compounds known in the field of polyurethane can be used without particular limitation. As the organic polyisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate,
4,4'-diphenylmethane diisocyanate, 1,5
-Aromatic diisocyanates such as naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate and m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6- Aliphatic diisocyanates such as hexamethylene diisocyanate, alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate and the like can be mentioned. Even if these are used in one kind,
It is possible to mix two or more kinds.

As the organic polyisocyanate, besides the above diisocyanate compound, a trifunctional or higher polyfunctional polyisocyanate compound can be used. As the polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) and trade name Duranate (manufactured by Asahi Kasei Corporation).

Among the above-mentioned diisocyanates, it is preferable to use 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI = HMDI) and toluene diisocyanate in combination as described above. Toluene diisocyanate is 2,4-toluene diisocyanate / 2,
6-toluene diisocyanate = 100/0 to 60/4
It is preferably 0 (molar ratio) in view of the characteristics of the foamed polyurethane.

Examples of the polyol compound include those usually used as a polyol compound in the technical field of polyurethane. For example, hydroxy-terminated polyester, polycarbonate, polyester carbonate, polyether, polyether carbonate,
In the technical field of polyurethane such as polyester amide, there are compounds known as polyols. Among them, it is preferable to use polyethers and polycarbonates having good hydrolysis resistance, lower cost, low melt viscosity and processed. Polyether is particularly preferable from the viewpoint of easy production.

As the polyether polyol, polytetramethylene glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PE
G) etc. are illustrated. Among these, PTMG is more preferably used because a polishing pad having excellent polishing characteristics can be obtained.

Examples of the polyester polyol include polybutylene adipate, polyhexamethylene adipate, polycaprolactone polyol and the like.

As the polyester polycarbonate polyester, a reaction product of a polyester glycol such as polycaprolactone polyol and an alkylene carbonate, ethylene carbonate and a polyhydric alcohol are used. The reaction product obtained by reacting and then reacting the obtained reaction mixture with an organic dicarboxylic acid is exemplified.

Examples of the polycarbonate carbonate include 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol and / or polytetramethylene glycol. Reaction products of diols such as phosgene, diallyl carbonate (eg diphenyl carbonate) or cyclic carbonates (eg propylene carbonate).

In the production of polyurethane foam having fine cells constituting the polishing layer, the above-mentioned polyols may be used alone or in combination of two or more kinds. If necessary, trifunctional or higher functional components may be used in combination.

The number average molecular weight of these polyols is not particularly limited, but is preferably 500 to 5,000, more preferably 700 to 3,000, from the viewpoint of the elastic properties of the polyurethane foam obtained. preferable.

When the number average molecular weight of the polyol is less than 500, the polyurethane foam obtained by using the polyol does not have sufficient elastic properties and is liable to become a brittle polymer, and a polishing pad using this polyurethane foam as a matrix is formed. It may become too hard and may cause scratches on the polishing surface of the workpiece to be polished. Further, it is easily worn, which is not preferable from the viewpoint of the life of the polishing pad.

On the other hand, when the number average molecular weight exceeds 5,000, the polishing pad having the polyurethane foam obtained by using the same as a matrix becomes soft and sufficient polishing characteristics cannot be obtained.

Further, as the constituent component of the foamed polyurethane, in addition to the above-mentioned polyol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol. , Neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene and other low molecular weight polyhydric alcohols. You may use together. These low molecular weight polyhydric alcohols may be used alone or in combination of two or more kinds.

In the present invention, the chain extender which is reacted with the isocyanate-terminated prepolymer to increase the molecular weight is an organic compound having at least two active hydrogen groups,
Examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, a thiol group (SH) and the like. Specifically, 4,4′-methylenebis (o-chloroaniline),
2,6-dichloro-p-phenylenediamine, 4,4 '
-Methylenebis (2,3-dichloroaniline), 3,5
-Bis (methylthio) -2,4-toluenediamine,
3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine,
3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,
2-bis (2-aminophenylthio) ethane, 4,4 '
Examples thereof include polyamines exemplified by -diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane and the like, or the above-mentioned low molecular weight polyols. These may be used alone or in combination of two or more.

An organic polyisocyanate according to the present invention,
The ratio of the polyol compound and the chain extender can be variously changed depending on the molecular weight of each and the desired physical properties of the polishing pad. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups in the organic polyisocyanate relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the polyol compound and the chain extender is in the range of 0.95 to 1.15. Is desirable, and it is more desirable that it is 0.99 to 1.10.

The ratio of the polyol to the low molecular weight polyhydric alcohol is appropriately set depending on the characteristics required for the polyurethane produced from them.

The foamed polyurethane is produced by a so-called prepolymer method, that is, a production method of preliminarily synthesizing an isocyanate-terminated prepolymer from an organic polyisocyanate and a polyol compound and reacting the prepolymer with a chain extender.

Isocyanate-terminated prepolymers prepared from organic polyisocyanates and polyol compounds are commercially available, but if they are compatible with the present invention, they are used in the present invention by the prepolymer method by the prepolymer method. It is also possible to polymerize polyurethane. The isocyanate-terminated prepolymer has a molecular weight of 800 to 50.
Those of about 00 are preferable because they have excellent workability and physical properties.

The isocyanate-terminated prepolymer is 2
May be used as a mixture of two or more, particularly in the production of polyurethane foam using an aliphatic or alicyclic diisocyanate and aromatic diisocyanate, with a prepolymer using an aliphatic or alicyclic diisocyanate Mixing a prepolymer using an aromatic diisocyanate is a preferred embodiment.

As a method of adjusting the residual ratio of the isocyanate monomer, for example, a prepolymer having a small residual ratio of the isocyanate monomer may be produced and the isocyanate monomer may be added to the prepolymer, or the residual ratio of the isocyanate monomer may be increased. Distillation from prepolymer,
You may remove an isocyanate monomer by pressure reduction etc.

A method of manufacturing the polishing pad of the present invention will be described. The method of manufacturing the polishing pad has the following steps. (1) Stirring step for preparing a bubble dispersion liquid of isocyanate-terminated prepolymer A silicon-based surfactant is added to the isocyanate-terminated prepolymer and stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles to form bubbles. Disperse liquid. When the prepolymer is solid at room temperature, it is preheated to an appropriate temperature and melted before use. (2) Hardener (Chain Extender) Mixing Step A chain extender is added to the above-mentioned bubble dispersion liquid and mixed and stirred to obtain a foaming reaction liquid. When the chain extender is a compound that is solid at room temperature, it is preferably added by melting. (3) Curing Step A foaming reaction liquid of an isocyanate-terminated prepolymer mixed with a chain extender is poured into a predetermined mold to be heat-cured.

When it is formed into a block shape during curing, it is cut into a sheet having a predetermined thickness and a predetermined size by a cutting step.

The sheet-like foamed polyurethane is provided with a laminating step of forming a cushion layer by adhering a flexible porous sheet or the like as needed before or after cutting to the size of the polishing pad. A layered polishing pad is manufactured.

Any known stirring device can be used without particular limitation as a stirring device for dispersing non-reactive gas in the form of fine bubbles in the isocyanate-terminated prepolymer containing a silicone surfactant in the stirring step. Examples thereof include a homogenizer, a dissolver, a two-axis planetary mixer (planetary mixer), and the like. The shape of the stirring blade of the stirring device is not particularly limited, but use of a whipper type stirring blade is preferable because fine bubbles can be obtained.

It is a preferable embodiment that different stirring devices are used for the stirring for preparing the bubble dispersion liquid in the stirring step and the stirring for adding and mixing the chain extender in the mixing step. In particular, the stirring in the mixing step may not be the stirring for forming bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such a stirring device,
A planetary mixer is preferred. Even if the same stirring device is used as the stirring device in the stirring process and the mixing process, there is no problem, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blades as needed before use. .

As the silicone-based surfactant used in the present invention, those which do not react with the polyurethane raw material and stably form fine bubbles can be used without limitation, but the physical properties of polyurethane are not impaired, A silicon-based surfactant is preferable from the viewpoint of stably forming uniform fine bubbles. In particular, a surfactant of a copolymer of silicon (polyalkylsiloxane) and polyether is preferable. Examples of the polyether here include polyethylene oxide, polypropylene oxide, and copolymers thereof. It is also preferable that the end of the polyether of the copolymer is a group which is inactive to an alkyl ether such as methyl ether and an isocyanate group such as an acetyl group. As such a silicon-based surfactant, a commercially available product can be used. For example, SH-192, SH-193.
(Manufactured by Toray Dow Corning Silicone Co., Ltd.) and the like are exemplified as preferable examples.

The non-reactive gas used in producing the foamed polyurethane is a gas composed of only a room temperature gas component that does not react with an isocyanate group or an active hydrogen group. The gas may be positively sent into the liquid, or only the situation in which the gas is naturally involved during stirring. As the non-reactive gas used to form the fine bubbles, those which are not flammable are preferable, and specifically, nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof are exemplified. The air that has been dried to remove moisture is most preferable in terms of cost.

In the present invention, a stabilizer such as an antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and other additives may be added to the polyurethane composition, if necessary. .

As a method for producing the polishing pad of the present invention,
First, a polyurethane block is produced by injecting a mixed liquid in which polyurethane raw materials are mixed into a mold and then causing the mixture to react and cure until it no longer flows. When foamed polyurethane is used, it is foamed together with curing. The foamed polyurethane block obtained can be heated and post-cured,
Such an operation has the effect of improving the physical properties of polyurethane and is extremely suitable. In the production of polyurethane foam,
A known catalyst that accelerates the polyurethane reaction may be used. The type of catalyst and the addition amount are appropriately selected.

Next, the obtained polyurethane foam block is sliced into a thickness suitable for a polishing pad (polishing layer). The polishing pad has a thickness of about 0.8 mm to 2 mm, and a sheet having a thickness of about 1.2 mm is usually used. In addition to this method, the polyurethane component may be cast into a mold having a cavity having the same thickness as the desired polishing pad.

A groove can be formed on the surface of the polishing pad, or a flexible porous sheet or the like can be attached to the back surface to form the polishing pad. The groove on the surface of the polishing pad has a function of releasing polishing dust and a polishing material from the contact surface between the object to be polished and the polishing sheet to the outside. The shape of the groove is not particularly limited, but the cross section may be rectangular, triangular, U-shaped, semicircular, or the like, and may have a cross-sectional area through which fine powder passes. The grooves are arranged on the sheet surface in a concentric shape, a grid shape, or the like. The depth of the groove depends on the thickness of the sheet, but is 0.4 to 0.8
It is about mm.

Examples of the flexible porous sheet to be laminated on the back surface include fibrous non-woven fabric layers such as polyester non-woven fabric, nylon non-woven fabric and acrylic non-woven fabric, or materials obtained by impregnating these non-woven fabrics with urethane resin, urethane resin, polyethylene resin and the like. A closed cell foam can be exemplified. Of these, urethane-impregnated polyester non-woven fabric, polyurethane foam or polyethylene foam is preferably used in terms of ease of production, inexpensiveness, stability of physical properties, and the like, and polyurethane closed-cell foam is particularly preferable.

[0054]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples.

[Evaluation Method] (Polishing Property) The polishing property of the polishing pad was evaluated using a CMP polishing apparatus SPP-600S (manufactured by Okamoto Machine Tool Co., Ltd.). Polishing conditions are as follows: Ceria slurry adjusted to pH 8 (Ceria sol manufactured by Nissan Chemical Co., Ltd.) is used as the slurry.
Polishing load of 350 g / cm while flowing at a flow rate of 0 g / min
² , polishing pad rotation speed 35 rpm, wafer rotation speed 33 r
It was done at pm. The polishing characteristics were evaluated by the average polishing rate. A polishing rate of 2000 Å / min or more was evaluated as a polishing property ◯, and a polishing rate of less than 2000 Å / min was evaluated as a polishing property x.

(Monomer residual rate) 10 mg of isocyanate-terminated prepolymer sample deactivated by reacting terminal isocyanate groups with methanol was added to 10 ml of TH.
After dissolving in F, the residual monomer ratio was determined from the peak area of the methanol reaction product of the isocyanate monomer using a GPC measuring device LC10A (manufactured by Shimadzu Corporation). The measurement was performed using a Plgel column (filler particle size 5 μm, pore size 50
0/100 / 50Å) and use 40μ of sample solution
l, THF was used as a solvent, and the flow rate was 1 ml / m.
It was measured in.

(Pot Life) The isocyanate-terminated prepolymer was heated to 60 ° C., and the molten 4,4′-methylenebis (o-chloroaniline) adjusted to 120 ° C. was added to NC.
Add and mix so that the O group / OH group equivalent ratio is 1.1, and cast the mixed solution on a glass plate heated to 50 ° C. to a thickness of about 5 mm. This liquid film is pierced with a square rod (about 3 mm square) three times, and the surface is observed for 10 seconds. The pot life was defined as the time when the fluidity of the liquid disappeared and the irregularities formed by piercing a square rod remained after 10 seconds.

(Evaluation of Moldability) In the following examples of the production of polishing pad materials, the curability of the foamable composition was poured into an open mold of a pan mold and molded. The moldability was evaluated as x when it was not completely spread in the mold.

(Examples 1 to 5 and Comparative Examples 1 to 6) <Production of Polishing Pad Material> Polytetramethylene glycol (hereinafter abbreviated as PTMG) having a number average molecular weight of 1000 and diethylene glycol (hereinafter abbreviated as DEG). ) In PTMG / DEG = 50/50 (molar ratio) as a glycol component, and the glycol component and toluene diisocyanate (2,4-body / 2,6-
Body = 80/20 mixture: hereinafter abbreviated as TDI), the TDI monomer after the reaction is used in an excessive amount so as to be heated and stirred at 80 ° C. for 120 minutes, and then distilled under reduced pressure to obtain an isocyanate monomer. Was removed to prepare an isocyanate-terminated TDI prepolymer. Separately, using the same glycol component, 4,4′-dicyclohexylmethane diisocyanate (hereinafter abbreviated as HMDI)
After the reaction, the HMDI monomer was used in an excess amount so as to have a predetermined amount, heated and stirred at 80 ° C. for 120 minutes, and then distilled under reduced pressure to remove the isocyanate monomer to prepare an isocyanate-terminated HMDI prepolymer.

The above two kinds of prepolymers were mixed so that the weight ratio of TDI prepolymer / HMDI prepolymer was 75/25, and further each isocyanate monomer was added so that each isocyanate monomer had a predetermined amount. As a raw material prepolymer for producing polyurethane foam.

A predetermined amount of a silicon surfactant SH-192 (manufactured by Toray Dow Corning Silicone Co., Ltd.) was added to 100 parts by weight of the obtained raw material prepolymer, mixed and adjusted to 80 ° C., and then a whipper type stirring blade. A viscous dispersion was prepared by vigorously stirring so that air bubbles could be taken in using a mixer having. Change the stirring device to a planetary mixer,
4,4′-methylenebis (o-chloroaniline) (hereinafter, abbreviated as MOCA) previously melted at 120 ° C. was added to this bubble dispersion liquid at an NCO / NH ₂ equivalent ratio of 1.
It was added so that it became 1 and stirred for about 1 minute. The obtained curable foam composition was put into a pan-type open mold and post-cured in an oven at 110 ° C. for 6 hours to prepare a polyurethane foam block. The foam system of this foamed polyurethane is approximately 40 to 50 μm and the density is 0.85.
Was about 0.90 g / cm ³ .

The residual ratio of the isocyanate monomer in the prepolymer and the HMDI monomer / TDI monomer ratio of the residual monomer are shown in the upper part of Table 1.

<Preparation of polishing pad> While the obtained foamed polyurethane block, which is a constituent material of the polishing pad, is heated to about 50 ° C., it is sliced to a thickness of 2 mm with a slicer (VGW-125 manufactured by Amitech Co., Ltd.). Then, a foamed polyurethane sheet was obtained. This sheet has a diameter of 610
cut into a circle with a width of 2.
0 mm, groove depth 0.6 mm, groove pitch 1.5 mm), concentric groove shape (groove width 0.3 mm, groove depth 0.4 mm, groove pitch 1.5 mm) Each one was manufactured. A cushioning material for a commercially available polishing pad was attached to the grooved polyurethane foam sheet with a double-sided tape to complete a polishing pad sample. The polishing rate was measured using the obtained polishing pad, and the evaluation results are summarized in Table 1.

[0064]

[Table 1] As is clear from Table 1, the polishing pad of the present invention showed good results in all evaluations. On the other hand, Comparative Examples 1 and 2 in which the residual isocyanate monomer ratio exceeds 20 wt% do not have satisfactory polishing characteristics, and the residual monomer HMDI / TDI weight ratio is 3 even when the residual isocyanate monomer ratio is 20 wt% or less. In Comparative Examples 3 and 4 exceeding 0.2, the curing was slow and the moldability was not satisfactory. In Comparative Example 5 in which the HMDI / TDI weight ratio was less than 0.5, the pot life was too short to perform molding.
In addition, Comparative Example 6 in which the addition amount of the silicon surfactant exceeds 5 wt%, is the isocyanate monomer residual rate,
Both HMDI / TDI weight ratios were within the range of the present invention, but the polishing characteristics were not satisfactory.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuyuki Ogawa             1-17-18 Edobori, Nishi-ku, Osaka City, Osaka Prefecture             Toyo Tire & Rubber Co., Ltd. (72) Inventor Takeshi Kimura             1-17-18 Edobori, Nishi-ku, Osaka City, Osaka Prefecture             Toyo Tire & Rubber Co., Ltd. (72) Inventor Koichi Ono             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. (72) Inventor Shigeru Komai             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. (72) Inventor Tetsuo Shimomura             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. F term (reference) 3C058 AA07 AA09 DA12 DA17                 4J034 BA08 CA04 CA15 CB03 CC03                       CC12 CC22 CC26 CC45 CC52                       CC61 CC65 CC67 CD13 DA01                       DB04 DB07 DC50 DF01 DF02                       DF16 DF20 DF24 DG03 DG04                       DG06 HA01 HA07 HA14 HC03                       HC12 HC13 HC17 HC22 HC46                       HC52 HC61 HC64 HC67 HC71                       HC73 JA03 JA42 NA08 NA09                       QB13 QB16 QC01 RA15

Claims (4)

[Claims] 1. A method for producing a foamed polyurethane polishing pad, comprising a step of adding a silicone-based surfactant to an isocyanate-terminated prepolymer, and stirring the mixture in the presence of a non-reactive gas to form a foam dispersion liquid. There is a mixing step of adding a chain extender to the cell dispersion and mixing it to obtain a foaming reaction solution, and a curing step of reacting and curing the foaming reaction solution, wherein the isocyanate monomer prepolymer has an isocyanate monomer content of 20% by weight. The following is a method for producing a foamed polyurethane polishing pad. 2. The isocyanate-terminated prepolymer uses, as an isocyanate component, at least one of an aliphatic diisocyanate and an alicyclic diisocyanate (first isocyanate component) and an aromatic diisocyanate (second isocyanate component), The ratio in the isocyanate monomer is the first isocyanate component / second isocyanate component = 0.5 to 3.2 (weight ratio).
The method for producing a foamed polyurethane polishing pad according to claim 1, wherein 3. The first isocyanate component is 4,4 ′.
The method for producing a foamed polyurethane polishing pad according to claim 2, wherein the second isocyanate component is dicyclohexylmethane diisocyanate, and the second isocyanate component is toluene diisocyanate. 4. The method for producing a foamed polyurethane polishing pad according to claim 1, wherein the addition amount of the silicon-based surfactant in the stirring step is 0.05 to 5% by weight. .