JP2003313352A - Polyamide foam, method for producing the same, and polishing pad comprising the foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide foam having a uniform foam structure and being usefully usable as a polishing pad being capable of improving the flatness and flattening efficiency of the surface to be polished, and having a longer life than the conventional. <P>SOLUTION: The polyamide foam is one comprising (a) dicarboxylic acid units containing 50-100 mol% terephthalic acid units and (b) diamine units containing 50-100 mol% 6-18C aliphatic diamine units and having a density of 0.4-0.95 g/cm<SP>3</SP>, a cell size of 20-200 μm, and a hardness (JIS-C hardness) of 93 or above. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide foam having a uniform foam structure, a method for producing the same, and a polishing pad made of the foam. The polishing pad of the present invention is useful for polishing applications for polishing a semiconductor wafer or the like with high accuracy and high efficiency.

[0002]

2. Description of the Related Art A polishing pad used for mirror-finishing a semiconductor wafer used as a base material for forming an integrated circuit is generally a velor-like or suede-like composite material of fiber and resin, or A relatively soft sheet, which is obtained by impregnating a non-woven fabric with a thermoplastic polyurethane resin and wet-solidifying it, has a large compression deformation characteristic and is relatively used.

In recent years, as semiconductor wafers have been highly integrated and multilayered, there has been an increasing demand for lower prices in addition to higher quality such as higher flatness. Along with this, polishing pads are required to have higher functionality such as flattening than ever before and to be usable for a long time.

The conventional relatively soft non-woven fabric type polishing pad has good contact with the wafer and good retention of the polishing slurry, but its flexibility does not sufficiently flatten the surface to be polished. . Moreover, the polishing slurry and polishing debris tend to clog the voids of the nonwoven fabric, which tends to cause scratches on the wafer surface. Further, the polishing slurry and polishing dust are easily clogged, and since they penetrate deep into the voids, it is difficult to clean them, and the polishing pad has a short use time.

On the other hand, a polishing pad using a polymer foam is also known, and has a higher rigidity than a non-woven type polishing pad, and therefore is often used in applications such as polishing of a wafer which requires flattening. There is. In addition, since the polishing pad using polymer foam has a closed cell structure, polishing slurry and polishing debris do not penetrate deep into the gap like non-woven type polishing pads, so cleaning of the polishing pad is relatively easy. It can withstand long-term use. In particular, polyurethane foam is often used as the polymer foam because of its excellent wear resistance.

[0006]

The foamed polyurethane polishing pad is usually manufactured by appropriately grinding or slicing the foamed polyurethane. Conventionally, foamed polyurethane for a polishing pad has been manufactured by cast-foaming and curing using a two-component curing type polyurethane (JP-A-2000-178374, JP-A-2000).
No. 248034, JP 2001-89548 A, JP 11-322878 A, etc.),
With this method, it is difficult to make the reaction and foaming uniform, and there is a limit to the increase in hardness of the obtained polyurethane foam.
Further, in the conventional polishing pad made of polyurethane foam, polishing characteristics such as flatness of the surface to be polished and flattening efficiency may change, and one of the causes is variation in the foam structure of the original polyurethane foam. Conceivable. Further, in order to improve the flattening efficiency, a polishing pad having a higher hardness is desired (see “[Science of CMP”, Science Forum Co., Ltd., issued August 20, 1997]).

The present invention has been made in view of the above circumstances, and has a uniform foam structure, can improve the flatness and flattening efficiency of the surface to be polished, and can reduce the operating time by the conventional method. It is an object of the present invention to provide a foam useful as a polishing pad, which foam can be extended more than the conventional one.

[0008]

As a result of repeated studies to achieve the above object, the inventors of the present invention foamed a specific polyamide in which a non-reactive gas was dissolved to obtain high hardness, fineness and fineness. The present invention was completed as a result of further studying that it was possible to obtain a foam having a uniform foam structure.

That is, the present invention provides a dicarboxylic acid unit (a) containing 50 to 100 mol% of terephthalic acid unit.
And an aliphatic diamine unit having 6 to 18 carbon atoms in an amount of 50 to 10
It is composed of a polyamide consisting of 0 mol% of the diamine unit (b) and has a density of 0.4 to 0.95 g / c.
m ³ , bubble size 20 to 200 μm, hardness (JIS-
Provided is a polyamide foam having a C hardness) of 93 or more, and a method for producing the same.

Further, according to the present invention, after the non-reactive gas is dissolved in the above polyamide under a pressurized condition, the pressure is released,
A polyamide foam having a density of 0.4 to 0.95 g / cm ³ and a cell size of 20 to 200 μm, which is obtained by foaming the polyamide at a temperature of a softening temperature or higher, and a method for producing the same. Further, the present invention provides a polishing pad made of the above polyamide foam.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The dicarboxylic acid unit (a) constituting the polyamide used in the present invention contains 50 to 100 mol% of a terephthalic acid unit. The content of the terephthalic acid unit in the dicarboxylic acid unit (a) is 75 to
It is preferably in the range of 100 mol%, and 90 to 1
It is more preferably within the range of 00 mol%. When the content of the terephthalic acid unit is less than 50 mol%, the heat resistance, water resistance, chemical resistance and the like of the obtained foam are deteriorated.

The above dicarboxylic acid unit (a) may contain a dicarboxylic acid unit other than the terephthalic acid unit as long as it is 50 mol% or less. Examples of the other dicarboxylic acid unit include malonic acid, dimethylmalonic acid, succinic acid,
Aliphatic dicarboxylic acids such as glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, 3,3-diethylsuccinic acid, azelaic acid, sebacic acid and suberic acid; 1,3
Alicyclic dicarboxylic acids such as cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid,
1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, diphenic acid, 4,4′-oxydibenzoic acid, diphenylmethane-4,4′-dicarboxylic acid,
Diphenyl sulfone-4,4'-dicarboxylic acid, 4,
A unit derived from an aromatic dicarboxylic acid such as 4′-biphenyldicarboxylic acid can be mentioned, and one or more of these can be used. Among these, it is preferable to use a unit derived from an aromatic dicarboxylic acid. The content of these other dicarboxylic acid units is preferably 25 mol% or less, and 1
It is more preferably 0 mol% or less. Furthermore, a unit derived from a polyvalent carboxylic acid such as trimellitic acid, trimesic acid, or pyromellitic acid may be contained within the range where melt molding is possible.

The diamine unit (b) constituting the polyamide used in the present invention contains 50 to 100 mol% of an aliphatic diamine unit having 6 to 18 carbon atoms. The content of the aliphatic diamine unit having 6 to 18 carbon atoms in the diamine unit (b) is preferably in the range of 75 to 100 mol%, more preferably 90 to 100 mol%. . When the content of the aliphatic alkylenediamine unit having 6 to 18 carbon atoms is less than 50 mol%, the heat resistance, water resistance, chemical resistance and the like of the obtained foam are deteriorated. Examples of the aliphatic diamine unit having 6 to 18 carbon atoms include 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, and , 11-
Undecanediamine, 1,12-dodecanediamine and other linear aliphatic alkylenediamines; 1-butyl-1,2
-Ethanediamine, 1,1-dimethyl-1,4-butanediamine, 1-ethyl-1,4-butanediamine, 1,
2-dimethyl-1,4-butanediamine, 1,3-dimethyl-1,4-butanediamine, 1,4-dimethyl-
1,4-butanediamine, 2,3-dimethyl-1,4-
Butanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2,5-
Dimethyl-1,6-hexanediamine, 2,4-dimethyl-1,6-hexanediamine, 3,3-dimethyl-
1,6-hexanediamine, 2,2-dimethyl-1,6
-Hexanediamine, 2,2,4-trimethyl-1,6
-Hexanediamine, 2,4,4-trimethyl-1,6
-Hexanediamine, 2,4-diethyl-1,6-hexanediamine, 2,2-dimethyl-1,7-heptanediamine, 2,3-dimethyl-1,7-heptanediamine, 2,4-dimethyl-1 , 7-heptanediamine,
2,5-dimethyl-1,7-heptanediamine, 2-methyl-1,8-octanediamine, 3-methyl-1,8
-Octanediamine, 4-methyl-1,8-octanediamine, 1,3-dimethyl-1,8-octanediamine, 1,4-dimethyl-1,8-octanediamine,
2,4-dimethyl-1,8-octanediamine, 3,4
-Dimethyl-1,8-octanediamine, 4,5-dimethyl-1,8-octanediamine, 2,2-dimethyl-
1,8-octanediamine, 3,3-dimethyl-1,8
-Octanediamine, 4,4-dimethyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine, and other branched chain aliphatic alkylenediamine units derived from these can be mentioned. 1 or 2
More than one species can be used.

Among the above-mentioned aliphatic alkylenediamine units, 1,6-hexanediamine, 1,8-octanediamine, 2-methyl-1,8-, from the viewpoint of obtaining a foam having excellent hardness and water resistance. Octanediamine, 1,9
-Nonanediamine, 1,10-decanediamine, 1,1
A unit derived from 1-undecanediamine or 1,12-dodecanediamine is preferable, an aliphatic diamine unit having 9 carbon atoms is more preferable, a 1,9-nonanediamine unit and / or 2-methyl-1,8-octanediamine. Units are more preferred.

The above diamine unit (b) is 50 mol%
If it is below, you may contain diamine units other than a C6-C18 aliphatic diamine unit. Examples of the other diamine units include aliphatic diamines such as ethylenediamine, propylenediamine, and 1,4-butanediamine; alicyclic rings such as cyclohexanediamine, methylcyclohexanediamine, isophoronediamine, norbornanedimethylamine, and tricyclodecanedimethylamine. Formula diamine; p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, m-xylylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-
Examples thereof include units derived from aromatic diamines such as diaminodiphenyl sulfone and 4,4′-diaminodiphenyl ether, and one or more of these can be used. The content of these other diamine units is preferably 25 mol% or less, more preferably 10 mol% or less.

The polyamide used in the present invention is
It is preferable that 10% or more of the terminal groups of the molecular chain be capped with a terminal capping agent. The rate at which the terminal groups of the molecular chain are blocked by the terminal blocking agent (terminal blocking rate) is more preferably 40% or more, and further preferably 60% or more. When a polyamide having a terminal sealing rate of 10% or more is used, a foam having more excellent heat resistance can be obtained.

The end-capping ratio of polyamide is determined by measuring the number of terminal carboxyl groups, terminal amino groups and end groups capped by a terminal capping agent, which are present in the polyamide. ) Can be obtained according to. The number of each terminal group is preferably determined by ¹ H-NMR from the integrated value of the characteristic signal corresponding to each terminal group in terms of accuracy and simplicity.

Terminal sealing rate (%) = [(A−B) / A] ×
100 (1) [wherein A represents the total number of terminal groups in the molecular chain (which is usually equal to twice the number of polyamide molecules), and B represents the terminal carboxyl groups and terminal amino groups remaining unsealed. Represents the total number of groups. ]

The terminal blocking agent is not particularly limited as long as it is a monofunctional compound having reactivity with an amino group or a carboxyl group at the polyamide terminal, but is not limited in terms of reactivity and stability of the terminal. Therefore, a monocarboxylic acid or a monoamine is preferable, and a monocarboxylic acid is more preferable from the viewpoint of easy handling. In addition, acid anhydrides, monoisocyanates, monoacid halides, monoesters, monoalcohols and the like can also be used.

The monocarboxylic acid used as the terminal blocking agent is not particularly limited as long as it has reactivity with an amino group, and examples thereof include acetic acid, propionic acid, butyric acid,
Valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid,
Aliphatic monocarboxylic acids such as pivalic acid and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, phenylacetic acid And other aromatic monocarboxylic acids; any mixture thereof, and the like. Among these,
In terms of reactivity, stability of sealed ends, price, etc., acetic acid,
Propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid and benzoic acid are preferred.

The monoamine used as the terminal blocking agent is not particularly limited as long as it has reactivity with a carboxyl group, and examples thereof include methylamine, ethylamine, propylamine, butylamine, hexylamine and octyl. Aliphatic monoamines such as amine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine and dibutylamine; cycloaliphatic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine and naphthylamine; And any mixture thereof. Among these, butylamine, hexylamine, octylamine, from the viewpoints of reactivity, high boiling point, stability of sealing end and price.
Decylamine, stearylamine, cyclohexylamine, aniline are preferred.

The polyamide used in the present invention is
It can be produced by any method known as a method for producing a crystalline polyamide. For example, it can be produced by a method such as a solution polymerization method using an acid chloride and a diamine as a raw material, an interfacial polymerization method, a melt polymerization method using a dicarboxylic acid and a diamine as a raw material, or a solid phase polymerization method.

Polyamides are, for example, firstly diamines,
A dicarboxylic acid, a catalyst and, if necessary, an end-capping agent are added all at once to produce a nylon salt.
Polymerization is carried out by heating at a temperature of 0 ° C. to give a prepolymer having an intrinsic viscosity [η] in concentrated sulfuric acid at 30 ° C. of 0.1 to 0.6 dl / g, and further solid phase polymerization or polymerization using a melt extruder. It can be manufactured by When the final stage of the polymerization is carried out by solid phase polymerization, it is preferably carried out under reduced pressure or under the flow of an inert gas. The polymerization temperature at this time is preferably in the range of 200 to 280 ° C.
Further, the polymerization temperature when the final stage of the polymerization is carried out by a melt extruder is preferably 370 ° C. or lower.

In producing the polyamide, phosphoric acid, phosphorous acid, hypophosphorous acid, salts or esters thereof, and the like can be added as a catalyst in addition to the above-mentioned end capping agent. As the above salt or ester,
Phosphoric acid, phosphorous acid or hypophosphorous acid and potassium, sodium, magnesium, vanadium, calcium, zinc,
Salts with metals such as cobalt, manganese, tin, tungsten, germanium, titanium and antimony; ammonium salts of phosphoric acid, phosphorous acid or hypophosphorous acid; ethyl esters of phosphoric acid, phosphorous acid or hypophosphorous acid, Examples thereof include isopropyl ester, butyl ester, hexyl ester, isodecyl ester, octadecyl ester, decyl ester, stearyl ester and phenyl ester.

The polyamide (A) used in the present invention is
The intrinsic viscosity [η] measured in concentrated sulfuric acid at 30 ° C.
It is preferably 0.4 to 3.0 dl / g, and 0.6
Is more preferably 2.0 to 2.0 dl / g, and 0.8 to
More preferably, it is 1.8 dl / g.

The polyamide foam of the present invention is obtained by foaming the polyamide described above and has a density of 0.4 to 0.95 g / cm ³ and a cell size of 20 to 20.
It satisfies 0 μm and hardness (JIS-C hardness) of 93 or more.

When the density is less than 0.4 g / cm ³ , the foam becomes too soft, and when used as a polishing pad, the flatness of the surface to be polished of the article after polishing deteriorates,
Further, the polishing efficiency is reduced. On the other hand, the density is 0.95 g / c
If it is larger than m ³ , the polishing efficiency is lowered. The density of the polyamide foam is 0.6 to 0.
More preferably, it is within the range of 9 g / cm ³ .

If the bubble size is smaller than 20 μm, the polishing agent (abrasive grains) is likely to be clogged in the bubbles, so that the polishing efficiency is lowered and polishing defects such as scratches are apt to occur. Since the smoothness deteriorates, the polishing agent (abrasive grains) is localized, and polishing defects such as scratches and orange peel scratches are likely to occur. The cell size of the polyamide foam is more preferably in the range of 50 to 150 μm from the viewpoint of retaining the abrasive (abrasive grains).

If the hardness is less than 93 (JIS C hardness), the polishing efficiency is insufficient and the object of the present invention cannot be achieved. From the viewpoint of polishing efficiency, the hardness of the polyamide foam is preferably 95 (JIS C hardness) or more,
More preferably, it is 97 (JIS C hardness) or more.

In the present invention, various foaming agents can be used for foaming the polyamide, but it is suitable to use the non-reactive gas from the viewpoint of stability at the temperature above the softening temperature of the polyamide. The non-reactive gas in the present invention is a gas that does not react with polyamide,
Examples of the gas include nitrogen, carbon dioxide, argon, helium and the like. Of these, carbon dioxide or nitrogen is preferable from the viewpoint of solubility in polyamide and production cost of the foam.

The polyamide foam of the present invention is produced by dissolving the above-mentioned non-reactive gas in the above-mentioned polyamide under pressure conditions, releasing the pressure, and foaming at a temperature above the softening temperature of the above-mentioned polyamide. can do. From the viewpoint of obtaining a foam having a uniform foam structure, the amount of the non-reactive gas to be dissolved is preferably a saturated amount under the dissolving conditions.

When a sheet-shaped molded product is used as the polyamide capable of dissolving a non-reactive gas, it is easy to produce a foamed product having a uniform foamed structure, and the process of forming a polishing pad can be simplified. It is advantageous. The sheet-shaped molded product is preferably one obtained by molding polyamide using an extrusion molding machine such as a uniaxial extrusion molding machine or a biaxial extrusion molding machine or an injection molding machine. The thickness of the sheet-shaped molded product is preferably in the range of 0.8 to 5 mm from the viewpoint of the ease of manufacturing the foam and the time required to dissolve the non-reactive gas.

The polyamide foam in the present invention is prepared by dissolving a non-reactive gas in a polyamide molded body in a pressure resistant container adjusted to a pressure of 5 to 20 MPa and a temperature of 80 to 200 ° C. It can be produced by releasing the pressure at a temperature lower than the softening temperature of the polyamide, and then heating the obtained molded body to a temperature not lower than the softening temperature of the polyamide to foam it [Production Method 1].

Although it depends on the composition of the polyamide, the size of the bubbles formed depends on the amount of dissolved non-reactive gas. The amount of non-reactive gas dissolved can be adjusted by the pressure and temperature at the time of dissolution. If the pressure of the non-reactive gas is less than 5 MPa,
It takes a long time to dissolve the non-reactive gas in the polyamide molded body in a saturated amount. On the other hand, the pressure of non-reactive gas is 20MP
When it exceeds a, the time required to dissolve the non-reactive gas is shortened, but the amount of the dissolved gas is unnecessarily large, and the size of the bubbles to be generated is significantly reduced. The pressure when the non-reactive gas is dissolved is preferably in the range of 8 to 18 MPa. Further, the temperature when the non-reactive gas is melted is 80
When the temperature is lower than 0 ° C, it takes a long time to dissolve the non-reactive gas in a saturated amount in the polyamide molded body. On the other hand, if the temperature at which the non-reactive gas is dissolved exceeds 200 ° C, partial foaming occurs when the pressure is released, or the amount of the non-reactive gas dissolved is significantly reduced, and the size of the bubbles generated increases. Pass. The temperature when the non-reactive gas is dissolved is 100 to 180.
It is preferably in the range of ° C.

In a molded body in which a non-reactive gas is dissolved,
When the heating temperature after releasing the pressure is lower than the softening temperature of polyamide, the generation and growth of bubbles are insufficient. The temperature at which the molded body in which the non-reactive gas is dissolved is heated is 200 to 2 in terms of the size of the generated bubbles and the strength of the foam.
It is preferably in the range of 80 ° C. There is no limitation on the heating and foaming method, but a method in which heat is uniformly applied to the molded body in which the non-reactive gas is dissolved is preferable in terms of ensuring the uniformity of the foamed structure. As the heating and foaming method, for example, a thermal oil bath,
Examples include a method of passing through a heating medium such as hot air or steam.

The polyamide foam according to the present invention has a pressure within the range of 10 to 30 MPa and a temperature within the range of 200 to.
It can also be produced by dissolving a non-reactive gas in a polyamide molded body in a pressure resistant container adjusted to a temperature of 280 ° C., and releasing the pressure from a pressurized state to atmospheric pressure for foaming. Manufacturing method 2].

Although it depends on the composition of the polyamide, the size of bubbles formed depends on the amount of dissolved non-reactive gas. The amount of non-reactive gas dissolved can be adjusted by the pressure and temperature at the time of dissolution. When the pressure when the non-reactive gas is dissolved is less than 10 MPa, it takes a long time to dissolve the non-reactive gas into the polyamide molded body in a saturated amount. On the other hand, if the pressure during dissolution of the non-reactive gas exceeds 30 MPa, the time required for the dissolution of the non-reactive gas will be shorter, but the amount of dissolved gas will be unnecessarily large and the size of the bubbles produced will be extremely small. Become. The pressure when the non-reactive gas is dissolved is 12 to 28 MPa.
It is preferably within the range. In addition, the temperature at which the non-reactive gas is dissolved and the pressure is released to cause foaming is 200
If the temperature is lower than 0 ° C, it takes a long time to dissolve the non-reactive gas in the polyamide molded body in a saturated amount, and the bubbles are not sufficiently generated or grown. On the other hand, when the temperature exceeds 280 ° C., the size of the bubbles generated varies and the obtained foam sheet body is deformed. The foaming temperature is 210
It is preferably in the range of to 260 ° C.

The polyamide foam according to the present invention can also be produced by dissolving a non-reactive gas in a molten polyamide under pressure and then extrusion-molding or injection-molding [Manufacturing method 3]. ].

At this time, the temperature at which the polyamide is melted is preferably in the range of 170 to 330 ° C. If the temperature to melt the polyamide is less than 170 ° C,
Substantial plasticity may not be obtained, and it may be difficult to melt the polyamide by screw kneading inside the extruder cylinder. On the other hand, when the temperature at which the polyamide is melted exceeds 330 ° C., decomposition gas is generated, and it may be difficult to obtain a foam having a uniform foam structure.
The temperature at which the polyamide is melted is preferably in the range of 180 to 310 ° C.

The pressure at which the non-reactive gas is dissolved in the molten polyamide is preferably in the range of 3 to 20 MPa, more preferably 5 to 18 MPa. If the pressure for dissolving the non-reactive gas is less than 3 MPa, the amount of the non-reactive gas dissolved in the molten polyamide tends to be small, and it tends to be difficult to obtain a foam substantially. . On the other hand, when the pressure when dissolving the non-reactive gas exceeds 20 MPa, the cell size of the obtained foam may be excessively small.

When a polyamide foam is manufactured by extrusion molding, the molten polyamide and the non-reactive gas are mixed inside the extrusion cylinder, and the unfoamed state is maintained inside the extrusion cylinder and inside the die. It is important that foaming occurs by being extruded from the to the atmospheric pressure. Foaming inside the extrusion cylinder or die increases the cell size, making it difficult to produce a uniform and fine foam. Therefore,
The non-reactive gas is injected into the extrusion cylinder, preferably from the center of the extrusion cylinder, and a pressure that does not cause foaming is maintained during the process from the injected portion to the extrusion of polyamide into the atmosphere at the die outlet. Is important. The pressure from the portion where the non-reactive gas is injected to the die outlet is preferably kept within the range of 3 to 20 MPa. In addition, when the polyamide is extruded from the die, if the viscosity of the molten polyamide in which the non-reactive gas is dissolved is low, the bubbles become large or break.
In order to obtain a foam having a uniform and fine foam structure,
It is preferable to adopt the conditions that can substantially extrude the molten polyamide in which the non-reactive gas is dissolved.

The polyamide foam can be produced by a general extrusion molding method such as T-die method, inflation method, profile extrusion method, tube extrusion method and the like. Above all, T
-The die method is preferable because it is easy to obtain a foamed sheet having a uniform thickness.

When a polyamide foam is manufactured by an injection molding method, if foaming occurs inside the injection cylinder, the cell size becomes large, and it becomes difficult to manufacture a uniform and fine foam. Therefore, it is important that the non-reactive gas is injected into the injection cylinder, preferably from the center of the injection cylinder, and in the process from the injected portion to the injection nozzle, it is important to maintain a pressure at which foaming does not occur.
The pressure from the portion where the non-reactive gas is injected to the injection nozzle is preferably kept within a range of 3 to 20 MPa.

When injection molding a molten polyamide in which a non-reactive gas is dissolved, injection is carried out at a low speed (injection speed at which the pressure decreases to a pressure at which foaming is possible during injection), so that the inside of the mold is simultaneously injected. Method for obtaining foam: After injecting at a high speed (injection speed at which a pressure at which foaming does not occur during injection is maintained) and cooling while maintaining the pressure, a molded body without foaming is produced, It is possible to employ a method in which foaming is caused by heating the molded product at a temperature above the softening temperature of polyamide to obtain a foamed product. Among these, from the viewpoint that a foam having a particularly uniform foam structure can be easily obtained, it is more preferable that the non-foam molded article obtained by injection under a high-speed condition is subjected to heat treatment to foam.

The polishing pad of the present invention is manufactured by grinding or slicing the polyamide foam manufactured as described above so that bubbles are exposed on the surface thereof. Further, the obtained polishing pad can be further processed into a predetermined shape, surface treatment, lamination with a material to be a cushion layer, and the like.

The polishing pad of the present invention is used together with a polishing slurry known per se in combination with chemical mechanical polishing (Chemical Mechanical Polishing).
Mechanical Polishing, which may be abbreviated as CMP hereinafter). The polishing slurry is, for example, a liquid medium such as water or oil; an abrasive such as aluminum oxide, cerium oxide, zirconium oxide, or silicon carbide;
Contains components such as bases, acids and surfactants. Further, when performing CMP, a lubricating oil, a cooling agent, etc. may be used together with the polishing slurry, if necessary.

CMP uses a known CMP apparatus,
This can be carried out by bringing the surface to be polished and the polishing pad into contact with each other via the polishing slurry at a constant speed and a predetermined time under pressure. The article to be polished is not particularly limited, but examples thereof include crystal, silicon, glass, optical substrate, electronic circuit substrate, multilayer wiring substrate, hard disk, and the like.

[0048]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The physical properties of the polyamide foams described in the examples were evaluated by the following methods.

<< Foam Density >> The density of the sheet-like foam was measured according to JIS K7112.

<< Cell Size of Foam >> The cross section of the foam was photographed by a scanning electron microscope, and the average cell size was calculated from the size measured on the photograph and the magnification at the time of photographing.

<< Hardness >> The hardness of polyamide is 2 mm in thickness.
The injection-molded sheet of
It was measured according to K 7311. The hardness of the polyamide foam was measured according to JIS K 7311 for JIS-C hardness.

<< Intrinsic viscosity >> 0.03 at 30 ° C. in concentrated sulfuric acid
The intrinsic viscosity was measured at concentrations of 5, 0.10, 0.20 and 0.40 g / dl, and the value obtained by extrapolating this to the concentration of 0 was taken as the intrinsic viscosity. The intrinsic viscosity is [ln (t ₁ /
t ₀ )] / c. (In the formula, t ₀ represents the solvent flow-down time (seconds), t ₁ represents the sample solution flow-down time (seconds), and c represents the sample concentration (g / dl) in the solution.)

Reference Example 1 16.37 kg (98.5 mol) of terephthalic acid, 16.37 kg (98.5 mol) of isophthalic acid, 26.92 kg (170 mol) of 1,9-nonanediamine, 2-methyl-1,8 -Octanediamine 4.74 (30 mol), benzoic acid 0.73 kg (6 mol), phosphorous acid 65 g and distilled water 60 liters were placed in an autoclave having an internal volume of 200 liters, and then the pressure vessel was replaced with nitrogen. Then 10
Stir for 30 minutes at 0 ° C, and keep the internal temperature at 210 ° C for 2 hours.
The temperature was raised to. After continuing the reaction for 1 hour, 230 ℃
Then, the temperature was maintained at 230 ° C. for 2 hours, and the steam was gradually removed to allow the reaction to proceed while maintaining the pressure at 2.2 MPa. Next, reduce the pressure to 1 MPa over 30 minutes,
By reacting for another 1 hour, the intrinsic viscosity is 0.25 dl
/ G of low-order condensate was obtained. The obtained low-order condensate was charged into a vacuum reactor and melt-polymerized at 280 ° C. and 13.3 Pa for 10 hours to obtain an intrinsic viscosity of 1.28 dl / g and a hardness (JI
A polyamide resin having an SD hardness of 80 (hereinafter abbreviated as PA-1) was manufactured.

Reference Example 2 32.73 kg (197 mol) of terephthalic acid, 1,9-
Nonanediamine 26.92 kg (170 mol), 2-methyl-1,8-octanediamine 4.74 (30 mol), benzoic acid 0.73 kg (6 mol), phosphorous acid 65
g and 60 liters of distilled water were replaced with nitrogen in an autoclave having an internal volume of 200 liters. The mixture was stirred at 100 ° C for 30 minutes, and the internal temperature was raised to 210 ° C over 2 hours. After continuing the reaction for 1 hour as it was, the temperature was raised to 230 ° C., and then the temperature was kept at 230 ° C. for 2 hours, and the reaction was carried out while gradually removing steam to keep the pressure at 2.2 MPa. Then 3
The pressure was reduced to 1 MPa over 0 minutes, and the reaction was continued for 1 hour to obtain a low-order condensate having an intrinsic viscosity of 0.25 dl / g. The low-order condensate obtained is crushed to 2 mm or less,
It was dried at 100 ° C. under reduced pressure for 12 hours, and then solid-state polymerized at 230 ° C. and 13.3 Pa for 10 hours using a tumbler type solid-state polymerization apparatus to obtain an intrinsic viscosity of 1.28 dl / g and a hardness (JIS- Polyamide resin having a D hardness of 80 (hereinafter PA-
2).

Reference Example 3 22.91 kg (138 mol) of terephthalic acid, 9.82 kg (59 mol) of isophthalic acid, 26.92 kg (170 mol) of 1,9-nonanediamine, 2-methyl-1,8
-Octanediamine 4.74 (30 mol), benzoic acid 0.73 kg (6 mol), phosphorous acid 65 g and distilled water 60 liter were replaced with nitrogen in an autoclave having an internal volume of 200 liter. The mixture was stirred at 100 ° C for 30 minutes, and the internal temperature was raised to 210 ° C over 2 hours. After continuing the reaction for 1 hour, the temperature was raised to 230 ° C.
Keep the temperature at ℃ and gradually remove the steam to reduce the pressure to 2.2M.
The reaction was performed while maintaining Pa. Next, the pressure was reduced to 1 MPa over 30 minutes, and the reaction was continued for 1 hour to obtain a low-order condensate having an intrinsic viscosity of 0.28 dl / g. The obtained low-order condensate is dried at 100 ° C. under reduced pressure for 12 hours, and then a twin-screw extruder [screw diameter 40 mm, L / D = 28, barrel temperature 310/320/330/330/330/33.
0/330/330 ° C, decompression in 7th zone (1330P
a) Vent, rotation speed 60 rpm] is supplied at a rate of 10 kg / hour to perform melt polycondensation, and the intrinsic viscosity is 1.35 dl /
A polyamide resin having a hardness of 78 and a hardness (JIS-D hardness) of 78 (hereinafter abbreviated as PA-3) was manufactured.

Reference Example 4 13.09 kg (79 mol) of terephthalic acid, 21.00 kg (118 mol) of azelaic acid, 26.92 kg (170 mol) of 1,9-nonanediamine, 2-methyl-1,
An autoclave having an internal volume of 200 liters was purged with 8-octanediamine 4.74 (30 moles), benzoic acid 0.73 kg (6 moles), phosphorous acid 65 g and distilled water 60 liters. The mixture was stirred at 100 ° C for 30 minutes, and the internal temperature was raised to 210 ° C over 2 hours. After continuing the reaction for 1 hour, the temperature was raised to 230 ° C.
Keep the temperature at ℃ and gradually remove the steam to reduce the pressure to 2.2M.
The reaction was performed while maintaining Pa. Next, the pressure was reduced to 1 MPa over 30 minutes, and the reaction was continued for 1 hour to obtain a low-order condensate having an intrinsic viscosity of 0.32 dl / g. The obtained low-order condensate is dried at 100 ° C. under reduced pressure for 12 hours, and then a twin-screw extruder [screw diameter 40 mm, L / D = 28, barrel temperature 310/320/330/330/330/33.
0/330/330 ° C, decompression in 7th zone (1330P
a) Vent, rotation speed 60 rpm] is supplied at a rate of 10 kg / hour to perform melt polycondensation, and the intrinsic viscosity is 1.45 dl /
A polyamide resin having a hardness of 73 and a hardness (JIS-D hardness) of 73 (hereinafter abbreviated as PA-4) was manufactured.

Example 1 The polyamide (PA-1) obtained above was charged into a single-screw extruder (65 mmφ), and the cylinder temperature was 270-2.
A sheet having a thickness of 2 mm was extruded from a T-die at 90 ° C. and a die temperature of 290 ° C. and passed through a roll having a temperature of 60 ° C. and a gap interval of 1.8 mm. Next, the obtained sheet (5 cm × 10 cm) was put in a pressure resistant container,
Carbon dioxide was dissolved for 10 hours under the conditions of a temperature of 150 ° C. and a pressure of 15 MPa to obtain a gas dissolution sheet obtained by dissolving carbon dioxide in a saturated amount. After cooling to room temperature, the pressure was brought to normal pressure, and the gas dissolving sheet was taken out from the pressure resistant container. Next, the obtained gas-dissolved sheet was immersed in silicone oil at 240 ° C. for 3 minutes and then taken out and cooled to room temperature to obtain a foam. The density of the obtained foam is 0.85 g / c
m ³ , bubble size 20 to 60 μm, hardness (JIS-C
The hardness) was 99. Obtained foam (sheet)
The surface of was ground to expose air bubbles on the surface to obtain a polishing pad.

Example 2 The polyamide (PA-1) obtained above was charged into an injection molding machine, and a sheet having a thickness of 2 mm was formed at a cylinder temperature of 260 to 290 ° C., a nozzle temperature of 290 ° C. and a mold temperature of 120 ° C. did. Next, the obtained sheet (5 cm × 10 cm) was placed in a pressure resistant container, carbon dioxide was dissolved for 10 hours under the conditions of a temperature of 140 ° C. and a pressure of 15 MPa to obtain a gas-dissolved sheet in which a saturated amount of carbon dioxide was dissolved. . After cooling to room temperature, the pressure was brought to normal pressure, and the gas dissolving sheet was taken out from the pressure resistant container. Next, 240
After immersing in silicone oil at ℃ for 4 minutes, take it out,
A foam was obtained by cooling to room temperature. The obtained foam has a density of 0.87 g / cm ³ , a cell size of 50 to 90 μm,
The hardness (JIS-C hardness) was 96. The surface of the obtained foam (sheet-like material) was ground to expose air bubbles on the surface to obtain a polishing pad.

Comparative Example 1 The polyamide (PA-4) obtained above was charged into a single-screw extruder (65 mmφ), and the cylinder temperature was 260 to 29.
Extruded from a T-die at 0 ° C and a die temperature of 290 ° C,
A sheet having a thickness of 2 mm was formed by passing through a roll having a gap interval of 1.8 mm, the temperature of which was adjusted to 60 ° C. Next, the obtained sheet (5 cm × 10 cm) was placed in a pressure resistant container, carbon dioxide was dissolved for 5 hours under the conditions of a temperature of 150 ° C. and a pressure of 15 MPa, and a saturated amount of carbon dioxide was dissolved to obtain a gas-dissolved sheet. It was After cooling to room temperature, make the pressure normal pressure,
The gas dissolving sheet was taken out of the pressure container. Next, the obtained gas-dissolved sheet was immersed in silicone oil at 240 ° C.
After soaking for 1 minute, it was taken out and cooled to room temperature to obtain a foam. The obtained foam has a density of 0.80 g / cm ³ , a cell size of 20 to 40 μm, and a hardness (JIS-C hardness) of 8
It was 9.

Example 3 Polyamide (PA-2) was added to a twin-screw co-directional extruder (48 mm).
φ) and melted at a cylinder temperature of 310 to 330 ° C., and at the same time, carbon dioxide was injected from the middle part of the cylinder at a pressure of 15 MPa, and after kneading, the temperature was adjusted to 290 ° C.
It was extruded from a T-die having a width of 0 cm, passed through a roll having a gap distance of 1.8 mm and adjusted to 60 ° C., and foamed simultaneously with molding to produce a foam sheet having a thickness of 2 mm. The sheet take-up speed at this time was 0.5 m / min.
The obtained foam had a density of 0.88 g / cm ³ , a cell size of 20 to 60 μm, and a hardness (JIS-C hardness) of 99. The surface of the obtained foam (sheet-like material) was ground to expose air bubbles on the surface to obtain a polishing pad.

Example 4 Polyamide (PA-3) was added to a twin-screw co-direction extruder (48 mm).
φ) and melted at a cylinder temperature of 260 to 290 ° C., at the same time, carbon dioxide was injected from the middle of the cylinder at a pressure of 10 MPa, and after kneading, the temperature was adjusted to 240 ° C. 4.
It was extruded from a T-die having a width of 0 cm, passed through a roll having a gap distance of 1.8 mm and adjusted to 60 ° C., and foamed simultaneously with molding to produce a foam sheet having a thickness of 2 mm. The sheet take-up speed at this time was 0.5 m / min.
The obtained foam had a density of 0.85 g / cm ³ , a cell size of 40 to 80 μm, and a hardness (JIS-C hardness) of 97. The surface of the obtained foam (sheet-like material) was ground to expose air bubbles on the surface to obtain a polishing pad.

Example 5 Polyamide (PA-3) was supplied to an injection molding machine and melted at a cylinder temperature of 260 to 290 ° C., and at the same time, carbon dioxide was injected and kneaded at a pressure of 10 MPa from the middle part of the cylinder, and then 50 ° C. 2 cm thick unfoamed sheet was poured into the temperature-controlled mold at a filling rate of 40 cm ³ / sec (filling time: 1.25 sec), cooled to room temperature, and then opened. Was manufactured. Next, the obtained sheet was immersed in silicone oil at 240 ° C. for 3 minutes and then cooled to room temperature to obtain a foam. The density of the obtained foam is 0.86 g / cm
³ , the bubble size was 50 to 90 μm, and the hardness (JIS-C hardness) was 96.

Comparative Example 2 Polyamide (PA-4) was added to a twin-screw co-directional extruder (48 mm).
φ) and melted at a cylinder temperature of 260 to 290 ° C., and at the same time, carbon dioxide was injected from the middle of the cylinder at a pressure of 15 MPa, and after kneading, the temperature was adjusted to 180 ° C. 4.
It was extruded from a T-die having a width of 0 cm, passed through a roll having a gap distance of 1.8 mm and adjusted to 60 ° C., and foamed simultaneously with molding to produce a foam sheet having a thickness of 2 mm. The sheet take-up speed at this time was 0.5 m / min.
The obtained foam had a density of 0.86 g / cm ³ , a cell size of 20 to 40 μm, and a hardness (JIS-C hardness) of 89.

[0064]

According to the present invention, a polyamide foam having a uniform foam structure, a method for producing the same, and a polishing pad made of the foam are provided. INDUSTRIAL APPLICABILITY The polishing pad of the present invention is useful for chemical mechanical polishing and can be used for the purpose of polishing a semiconductor wafer or the like with high accuracy and high efficiency. The polishing pad of the present invention, in particular, can achieve the flatness of the surface to be polished and the improvement of the flattening efficiency,
Moreover, the usage time can be extended as compared with the conventional one.

Continued front page    F-term (reference) 3C058 AA07 AA09 CB01 DA17                 4F071 AA55 AB17 AB22 AE01 AH19                       DA20                 4F074 AA71 BA31 BA32 BA33 BA84                       CA22 CA26 DA02 DA03 DA56

Claims (12)

[Claims] 1. 50 to 100 mol% of terephthalic acid unit
A dicarboxylic acid unit (a) contained and a diamine unit (b) containing 50 to 100 mol% of an aliphatic diamine unit having 6 to 18 carbon atoms, and a polyamide having a density of 0.4 to 0.95 g. / Cm ³ , bubble size 20 ~
A polyamide foam having a hardness of 200 μm and a hardness (JIS-C hardness) of 93 or more. 2. 50 to 100 mol% of terephthalic acid units
A non-reactive gas is dissolved in a polyamide composed of a dicarboxylic acid unit (a) contained therein and a diamine unit (b) containing 50 to 100 mol% of an aliphatic diamine unit having 6 to 18 carbon atoms under a pressurized condition. After that, the pressure is released, and the polyamide is foamed at a temperature equal to or higher than the softening temperature, the density is 0.4 to 0.95 g / cm ³ , and the cell size is 20 to 20.
A polyamide foam having a size of 0 μm. 3. The foam according to claim 2, wherein the polyamide that dissolves the non-reactive gas is a sheet-shaped molded body. 4. The foam according to claim 2 or 3, wherein the polyamide that dissolves the non-reactive gas is a polyamide in a molten state. 5. The foam according to claim 2, wherein the non-reactive gas is carbon dioxide or nitrogen. 6. The aliphatic diamine unit having 6 to 18 carbon atoms is mainly an aliphatic diamine unit having 9 carbon atoms.
5. The foam according to any one of 5 to 5. 7. A polishing pad made of the foam according to any one of claims 1 to 6. 8. A terephthalic acid unit is 50 to 100 mol%.
In a pressure-resistant container, a sheet-shaped molded product made of a polyamide composed of a dicarboxylic acid unit (a) contained therein and a diamine unit (b) containing 50 to 100 mol% of an aliphatic diamine unit having 6 to 18 carbon atoms was prepared. , The pressure is 5 to 20 MPa,
A step of dissolving a non-reactive gas in a saturated amount under the condition of a temperature of 80 to 200 ° C., a step of releasing the pressure of the pressure resistant container at a temperature lower than the softening temperature of the polyamide, and a temperature not lower than the softening temperature of the thermoplastic polyamide. A method for producing a polyamide foam, which comprises a step of foaming a sheet-shaped molded product in which a saturated amount of the non-reactive gas is dissolved by heating. 9. 50 to 100 mol% of terephthalic acid units
In a pressure-resistant container, a sheet-shaped molded product made of a polyamide composed of a dicarboxylic acid unit (a) contained therein and a diamine unit (b) containing 50 to 100 mol% of an aliphatic diamine unit having 6 to 18 carbon atoms was prepared. , Pressure is 10 ~ 30MP
a, a step of dissolving a non-reactive gas in a saturated amount under the condition of a temperature of 200 to 280 ° C., and a step of releasing the pressure of the pressure vessel to foam a sheet-shaped molded article in which the non-reactive gas is dissolved in a saturated amount. A method for producing a polyamide foam containing the same. 10. A dicarboxylic acid unit (a) containing 50 to 100 mol% of a terephthalic acid unit, and 6 to 18 carbon atoms.
A step of dissolving a non-reactive gas in a molten polyamide comprising a diamine unit (b) containing 50 to 100 mol% of an aliphatic diamine unit under pressure, and a polyamide in which the non-reactive gas is dissolved. Method for producing a polyamide foam having a density of 0.4 to 0.95 g / cm ³ and a cell size of 20 to 200 μm, including a step of obtaining an expanded molded article by extrusion molding or injection molding under a pressure capable of foaming . 11. A dicarboxylic acid unit (a) containing 50 to 100 mol% of a terephthalic acid unit, and 6 to 18 carbon atoms.
Of a diamine unit (b) containing 50 to 100 mol% of the aliphatic diamine unit, and a step of dissolving a non-reactive gas in a molten state under pressure conditions, foaming the polyamide in which the non-reactive gas is dissolved. Of a density of 0. 4-0.9
A method for producing a polyamide foam having a cell size of 5 g / cm ³ and a cell size of 20 to 200 μm. 12. The method for producing a polyamide foam according to claim 8, wherein the non-reactive gas is carbon dioxide or nitrogen.