Polyurethane foam, buffering material, and semiconductor polishing member

Abstract

The present invention provides a polyurethane foam which secures flexibility, while having sufficient hardness. The polyurethane foam is obtained from a composition that contains a polyol and an isocyanate. The polyol includes: a polymer polyol; a polyester polyol having a number average molecular weight of more than 250; and a polyol having a number average molecular weight or a molecular weight of 250 or less. The content of the polyol having a number average molecular weight or a molecular weight of 250 or less is 15 parts by mass or more when the whole polyol is taken as 100 parts by mass.

Description

Polyurethane foam, buffer material, and semiconductor polishing material

[0001] The present disclosure relates to a polyurethane foam, a buffer material, and a semiconductor polishing member.

[0002] Patent Document 1 discloses a polishing pad having a polishing layer and an elastic layer having a lower hardness than the polishing layer laminated together, in which an elastic layer made of polyurethane is used as the elastic layer.

[0003] WO 2007 / 034980

[0004] The elastic layer for conventional polishing pads does not have sufficient hardness, which can cause uneven polishing during the polishing process. However, when an attempt is made to increase the hardness of a polyurethane foam by increasing the crosslink density, for example, by using a hyperbranched polyol, there is a problem that the flexibility decreases as the crosslink density increases.

[0005] The present disclosure has been made in view of the above circumstances, and aims to solve at least one of the above problems. The present disclosure can be realized in the following aspects.

[0006] [1] A polyurethane foam obtained from a composition containing a polyol and an isocyanate, wherein the polyol contains a polymer polyol, a polyester polyol having a number-average molecular weight of more than 250, and a polyol having a number-average molecular weight or a molecular weight of 250 or less, and the content of the polyol having a number-average molecular weight or a molecular weight of 250 or less is 15 parts by mass or more, when the total amount of the polyol is 100 parts by mass.

[0007] The present disclosure can solve at least one of the above problems. For example, the present disclosure can provide a polyurethane foam that has sufficient hardness while ensuring flexibility.

[0008] 1 is a cross-sectional view schematically illustrating a semiconductor polishing member according to one embodiment.

[0009] Here, preferred examples of the present disclosure are described. [2] The polyurethane foam according to [1], wherein the polyol having a number average molecular weight or a molecular weight of 250 or less contains a polyol having more than two functional groups. [3] The polyurethane foam according to [1] or [2], wherein the isocyanate contains urethane-modified MDI. [4] A buffer material comprising the polyurethane foam according to any one of [1] to [3]. [5] A semiconductor polishing member comprising a polishing pad for polishing a semiconductor material, a polishing plate for rotating the polishing pad, and the buffer material according to [4], laminated between the polishing pad and the polishing plate.

[0010] The present disclosure will be described in detail below. In this specification, when a numerical range is indicated using "-", it is assumed that the range includes both the lower limit and the upper limit unless otherwise specified. For example, the expression "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less". In addition, in this specification, the upper limit and lower limit of each numerical range can be combined in any way.

[0011] 1. Polyurethane Foam The polyurethane foam is obtained from a composition containing a polyol and an isocyanate. The polyol includes a polymer polyol, a polyester polyol having a number-average molecular weight of more than 250, and a polyol having a number-average molecular weight or a molecular weight of 250 or less. The content of the polyol having a number-average molecular weight or a molecular weight of 250 or less is 15 parts by mass or more, based on 100 parts by mass of the total polyol.

[0012] (1) Polyol The polyol includes a polymer polyol, a polyester polyol having a number average molecular weight of more than 250 (hereinafter also simply referred to as a polyester polyol), and a polyol having a number average molecular weight or a molecular weight of 250 or less (hereinafter also referred to as a low molecular weight polyol). The polyol may further include a polyol other than the above-mentioned polymer polyol, polyester polyol, and low molecular weight polyol.

[0013] (1.1) Polymer Polyol The polyol includes a polymer polyol. Only one type of polymer polyol may be included, or two or more types may be included. By using a polymer polyol, for example, compared to the case where a hyperbranched polyol is used, the hardness of the polyurethane foam can be suitably increased without excessively increasing the crosslink density. In addition, polymer polyols have good compatibility with other components, and are less likely to cause problems such as separation and sedimentation of the composition.

[0014] The polymer polyol is, for example, a polyol containing finely divided polymer particles dispersed in the polyol. The finely divided polymer may be, for example, one or more polymers selected from styrene, acrylonitrile, acrylic, and melamine, or may be polyurea. The polymer polyol is preferably a mixture of styrene and / or acrylonitrile with a polyether polyol (base polyol). At least a portion of the styrene and / or acrylonitrile may be polymerized in the base polyol. The base polyol is, for example, a polyether polyol. A specific example of a polyether polyol is a polyether polyol containing propylene oxide units and / or ethylene oxide units as alkylene oxide units. The mass ratio of styrene to acrylonitrile (styrene:acrylonitrile) is, for example, 0:100 to 50:50.

[0015] The polymer content of the polymer polyol is not particularly limited. The polymer content of the polymer polyol refers to the mass ratio of the portion other than the base polyol to the entire polymer polyol. The polymer content of the polymer polyol is, for example, 10% by mass or more and 55% by mass or less. From the viewpoint of increasing the hardness of the polyurethane foam, the polyol preferably contains a polymer polyol with a polymer content of 25% by mass or more, more preferably a polymer polyol with a polymer content of 35% by mass or more, and even more preferably a polymer polyol with a polymer content of 40% by mass or more. The polymer content (mass%) is also simply referred to as the resin content (%).

[0016] The number average molecular weight, hydroxyl value, and number of functional groups of the polymer polyol are not particularly limited. The number average molecular weight of the polymer polyol is usually greater than 250, preferably 1,000 to 10,000, more preferably 2,000 to 6,000, and even more preferably 2,500 to 4,500. The number average molecular weight of the polymer polyol is defined as the number average molecular weight of the base polyol. The hydroxyl value of the polymer polyol is preferably 15 mg KOH / g to 150 mg KOH / g, more preferably 20 mg KOH / g to 100 mg KOH / g, and even more preferably 25 mg KOH / g to 50 mg KOH / g. From the viewpoint of reducing crosslink density, the number of functional groups of the polymer polyol is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and may be less than 3. The number of functional groups of the polymer polyol is usually 2 or more.

[0017] The content of polymer polyol is not particularly limited. The content of polymer polyol is preferably 20 parts by mass or more and 80 parts by mass or less, more preferably 30 parts by mass or more and 70 parts by mass or less, and even more preferably 40 parts by mass or more and 60 parts by mass or less, when the total polyol is taken as 100 parts by mass. Among the polymer polyols, the content of polymer polyols having a polymer content of 25% by mass or more is preferably 15 parts by mass or more and 75 parts by mass or less, more preferably 20 parts by mass or more and 65 parts by mass or less, and even more preferably 35 parts by mass or more and 55 parts by mass or less, when the total polyol is taken as 100 parts by mass.

[0018] The total amount of resin components derived from polymer polyol is preferably 17% by mass or more, more preferably 18% by mass or more, when the total polyol is 100% by mass. The upper limit of the amount of resin components derived from polymer polyol is not particularly limited, and is, for example, 50% by mass or less, 40% by mass or less, or 30% by mass or less. The amount of resin components derived from polymer polyol can be calculated by multiplying the polymer content of the polymer polyol by the mass ratio of the polymer polyol. When two or more polymer polyols are contained, the amount of resin components derived from each polymer polyol can be added together to calculate the total amount of resin components derived from polymer polyol.

[0019] (1.2) Polyester Polyol The polyol contains a polyester polyol having a number average molecular weight exceeding 250. Only one type of polyester polyol may be contained, or two or more types may be contained. By using a polyester polyol in combination with a low molecular weight polyol, it is possible to suitably achieve both high hardness and flexibility. The reason for this is unclear, but it is presumed that the polar moiety of the ester group partially forms a hydrogen bond with the polar group on the hard segment of the crosslinked portion (urethane bond). The technology of the present disclosure is not limited to this presumed reason.

[0020] The polyester polyol is, for example, one or more selected from the group consisting of ring-opening polymers of cyclic esters and polymers obtained by condensation of polyfunctional carboxylic acids with polyfunctional hydroxy compounds. A specific example of a ring-opening polymer of a cyclic ester is a polycaprolactone-based polyester polyol obtained by ring-opening addition polymerization of lactones such as ε-caprolactone. A specific example of a polymer obtained by condensation of a polyfunctional carboxylic acid with a polyfunctional hydroxy compound is an adipate-based polyester polyol. Among these, from the viewpoint of hydrolysis resistance, the polyester polyol is more preferably a polycaprolactone-based polyester polyol.

[0021] From the viewpoint of flexibility of the polyurethane foam, the number average molecular weight of the polyester polyol is greater than 250, and may be 300 or more, 400 or more, or 450 or more. The upper limit of the number average molecular weight of the polyester polyol is not particularly limited. From the viewpoint of increasing the hardness of the polyurethane foam, the upper limit of the number average molecular weight of the polyester polyol is preferably less than 1500, more preferably 1000 or less, and even more preferably 800 or less. The number average molecular weight of the polyester polyol is preferably greater than 250 and 1500 or less, and can be within a range that appropriately combines the above lower limit and upper limit.

[0022] The hydroxyl value and the number of functional groups of the polyester polyol are not particularly limited. The hydroxyl value of the polyester polyol is preferably 60 mgKOH / g or more and 350 mgKOH / g or less, more preferably 80 mgKOH / g or more and 300 mgKOH / g or less, and even more preferably 100 mgKOH / g or more and 250 mgKOH / g or less. From the viewpoint of reducing the crosslink density, the number of functional groups of the polyester polyol is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and may be less than 3. The number of functional groups of the polyester polyol is usually 2 or more.

[0023] The content of the polyester polyol is not particularly limited, and is preferably 10 parts by mass or more and 55 parts by mass or less, more preferably 15 parts by mass or more and 45 parts by mass or less, even more preferably 20 parts by mass or more and 40 parts by mass or less, and particularly preferably 20 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the total polyol.

[0024] (1.3) Low-Molecular-Weight Polyol The polyol contains a polyol having a number-average molecular weight or a molecular weight of 250 or less. Only one type of low-molecular-weight polyol may be contained, or two or more types may be contained. The low-molecular-weight polyol is presumed to act as a chain extender and / or a crosslinking agent, thereby increasing the hardness of the polyurethane foam.

[0025] The low-molecular-weight polyol may be a polyol having two functional groups, or may be a polyol having more than two functional groups. The polyol having two functional groups is, for example, one or more selected from the group consisting of dipropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-butanediol, and 1,4-butanediol. Of these, dipropylene glycol is preferred. The polyol having more than two functional groups is, for example, one or more selected from the group consisting of glycerin, trimethylolpropane, pentaerythritol, sorbitol, triethylene glycol, monomer polyols of trimethylolpropane propylene oxide modified products, and pentaerythritol propylene oxide modified products. Of these, glycerin is preferred.

[0026] From the viewpoint of increasing the hardness of the polyurethane foam, the low-molecular-weight polyol preferably contains a polyol having a functionality of more than 2. From the viewpoint of increasing the hardness of the polyurethane foam and ensuring flexibility, the content of the polyol having a functionality of more than 2 is preferably 0.0010 mol or more and 0.1000 mol or less, more preferably 0.0015 mol or more and 0.0500 mol or less, and even more preferably 0.0020 mol or more and 0.0250 mol or less, based on 100 parts by mass of the total polyols.

[0027] From the viewpoint of adjusting the crosslink density, the low-molecular-weight polyol more preferably contains both a polyol having a functionality of 2 and a polyol having a functionality of more than 2. The mass ratio of the polyol having a functionality of 2 to the polyol having a functionality of more than 2 (polyol having a functionality of 2:polyol having a functionality of more than 2) is preferably 99.9:0.1 to 90:10, more preferably 99.5:0.5 to 92:8, and even more preferably 99:1 to 94:6.

[0028] The content of the low-molecular-weight polyol is 15 parts by mass or more, where the total amount of polyols is 100 parts by mass. The upper limit of the content of the low-molecular-weight polyol is not particularly limited, and may be, for example, 30 parts by mass or less, 25 parts by mass or less, 20 parts by mass or less, or 18 parts by mass or less.

[0029] (2) Isocyanate Isocyanate is a compound having a plurality of isocyanate groups. The isocyanate may be any of aromatic, alicyclic, and aliphatic isocyanates. The isocyanate may be an isocyanate having two functional groups or an isocyanate having more than two functional groups. Only one type of isocyanate may be used, or two or more types may be used.

[0030] Examples of isocyanates having two functional groups include 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate (MDI), 2,2'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate (TDI), m-phenylene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, and 3,3'-dimethyl-4,4'-biphenylene diisocyanate. and one or more selected from the group consisting of methyl cyclohexane diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, lysine isocyanate, and modified products thereof.

[0031] Examples of the isocyanate having more than two functional groups include one or more selected from the group consisting of polymethylene polyphenylisocyanate (polymeric MDI), 1-methylbenzol-2,4,6-triisocyanate, 1,3,5-trimethylbenzol-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'tetraisocyanate, and triphenylmethane-4,4',4"-triisocyanate, and modified versions thereof.

[0032] From the viewpoint of reactivity, the isocyanate preferably contains urethane-modified MDI, and from the viewpoint of ensuring reactivity and an appropriate crosslink density, it more preferably contains urethane-modified polymeric MDI. The urethane-modified MDI can be obtained by reacting MDI or polymeric MDI with polyols. The urethane-modified MDI is also called MDI prepolymer, etc. Note that the polyols used to obtain the urethane-modified MDI are not considered to be polyols contained in the composition.

[0033] The isocyanate index is preferably 80 to 130, more preferably 90 to 120. The isocyanate index is calculated by [(isocyanate equivalent in the composition / active hydrogen equivalent in the composition)×100].

[0034] (3) Resin Modifier The composition may contain a resin modifier. From the viewpoint of improving impact resistance and rigidity, the resin modifier is preferably a resin modifier containing polymer particles having a core-shell structure. Polymer particles having a core-shell structure specifically refer to rubber particles in which a particulate core component, mainly composed of a crosslinked rubbery polymer, is graft-polymerized with a polymer different from the core component to partially or entirely coat the surface of the particulate core component with a shell component. Examples of the core component include crosslinked rubber particles. The type of rubber used for the crosslinked rubber particles is not limited, and examples include butadiene rubber, acrylic rubber, silicone rubber, butyl rubber, nitrile rubber, styrene rubber, synthetic natural rubber, ethylene propylene rubber, etc. Examples of the shell component include polymers polymerized from one or more monomers selected from the group consisting of acrylic acid esters, methacrylic acid esters, and aromatic vinyl compounds. It is preferable that the shell component be graft-polymerized to the core component and chemically bonded to the polymer constituting the core component. In addition, in consideration of dispersibility in polyol, it is preferable that the core-shell rubber particles contain an MBS (methyl methacrylate-butadiene-ethylene copolymer) polymer.

[0035] The particle size (volume average particle size) of the polymer particles is preferably from 10 nm to 2,000 nm, more preferably from 50 nm to 800 nm, still more preferably from 100 nm to 600 nm, and particularly preferably from 200 nm to 400 nm.

[0036] The content of the polymer particles is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 1.5 parts by mass or more and 8.0 parts by mass or less, and even more preferably 2.0 parts by mass or more and 6.0 parts by mass or less, relative to 100 parts by mass of the total polyol.

[0037] To facilitate mixing with polyols and the like, the polymer particles are preferably dispersed in polypropylene glycol and added to the polyurethane foam composition as a polymer particle dispersion. The polypropylene glycol in the polymer particle dispersion functions as a solvent. This polypropylene glycol is usually not a "polyol with a number average molecular weight or a molecular weight of 250 or less," but rather, for example, a polypropylene glycol with a number average molecular weight of 350-500. The mass ratio of the polymer particles to the polypropylene glycol (polymer particles:polypropylene glycol) in the polymer particle dispersion is preferably 40:60-50:50. When the solvent for the core-shell rubber particle dispersion is a polyol, this polyol is considered to be included in the polyol contained in the composition.

[0038] The content of the polymer particle dispersion is preferably 1.0 parts by mass or more and 20 parts by mass or less, more preferably 2.0 parts by mass or more and 15 parts by mass or less, and even more preferably 3.0 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total polyol.

[0039] (4) Filler The composition may contain a filler. The filler is preferably one or more selected from the group consisting of aluminum hydroxide, magnesium hydroxide, and calcium carbonate. The content of the filler is preferably 5.0 parts by mass or more and 30 parts by mass or less, more preferably 10 parts by mass or more and 25 parts by mass or less, and even more preferably 15 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the total polyol.

[0040] (5) Foam Stabilizer The composition may contain a foam stabilizer. The foam stabilizer is used to facilitate the foaming of the polyurethane foam composition. As the foam stabilizer, a known foam stabilizer that is normally used when a mechanical froth method is employed, such as a silicone-based foam stabilizer, can be used. The content of the foam stabilizer is preferably 1.0 parts by mass or more and 25 parts by mass or less, more preferably 2.0 parts by mass or more and 10 parts by mass or less, and even more preferably 2.5 parts by mass or more and 5 parts by mass or less, based on 100 parts by mass of the total polyol.

[0041] (6) Catalyst The composition may contain a catalyst. The catalyst is primarily intended to promote the urethane reaction between the polyol and the isocyanate. The organometallic catalyst is preferably at least one selected from the group consisting of an organoiron compound, an organonickel compound, an organotin compound, an organobismuth compound, an organolead compound, and an organozinc compound. The content of the catalyst is preferably 1.0 part by mass or more and 20 parts by mass or less, more preferably 2.0 parts by mass or more and 10 parts by mass or less, and even more preferably 3.0 parts by mass or more and 6.0 parts by mass or less, based on 100 parts by mass of the total polyol.

[0042] (7) Antioxidant The composition may contain an antioxidant. From the viewpoint of reducing the content of volatile organic compounds, the antioxidant is preferably a hindered phenol-based antioxidant. The content of the antioxidant is preferably 0.05 parts by mass or more and 1.0 parts by mass or less, more preferably 0.08 parts by mass or more and 0.5 parts by mass or less, and even more preferably 0.1 parts by mass or more and 0.3 parts by mass or less, based on 100 parts by mass of the total polyol.

[0043] (8) Moisture absorbent The composition may contain a moisture absorbent. The moisture absorbent is preferably an inorganic porous material that is solid at room temperature and that supports a metal compound. Supporting refers to a state in which the metal compound is held by the inorganic porous material by physical or chemical adsorption. The inorganic porous material is made of zeolite, sepiolite, aluminum oxide, silica, etc., and has a physical adsorption function. The content of the moisture absorbent is preferably 0.3 parts by mass or more and 3.0 parts by mass or less, more preferably 0.5 parts by mass or more and 2.0 parts by mass or less, and even more preferably 0.8 parts by mass or more and 1.5 parts by mass or less, based on 100 parts by mass of the total polyol.

[0044] (9) Other Components The composition may contain other components in addition to those described above, as necessary. Examples of the other components include additives such as foaming aids (e.g., zinc stearate, urea-based foaming aids), dispersants (e.g., polyethylene wax), crosslinking aids, pigments, plasticizers, and function-imparting agents (e.g., flame retardants).

[0045] (10) Number-average molecular weight or molecular weight of polyol In the present disclosure, the "number-average molecular weight" of a polyol can be measured, for example, by gel permeation chromatography (GPC). The "molecular weight" is calculated as the sum of the atomic weights of the atoms constituting the molecule. When the polyol is commercially available, the catalog value may be used as the number-average molecular weight or molecular weight.

[0046] 2. Physical properties of polyurethane foam (1) Apparent density The apparent density of polyurethane foam (JIS K6401:2011) is 100 kg / m ３ More than 200 kg / m ３ More preferably, 300 kg / m or more ３ More preferably, 350 kg / m ３ More than 400kg / m ３ The apparent density of the polyurethane foam may be 900 kg / m or more. ３ Preferably, less than 800 kg / m ３ More preferably, 750 kg / m or less ３ More preferably, 700 kg / m or less ３ Below, 600kg / m ３ Below, 500kg / m ３ Below, 450kg / m ３ The apparent density of the polyurethane foam may be within a range that is an appropriate combination of the above lower and upper limits.

[0047] (2) 25% Compression Hardness (CLD) 25% compression hardness (CLD (Compression-Load-Deflection)) can be measured based on JIS K6254:2010. For example, 25% compression hardness can be measured as follows. The test specimen is cylindrical with a diameter of 50 mm. Three test specimens are used. For measurement, a compression tester is used in which the built-in compression hardness measuring jig contacts the test specimen, and at the same time, the load cell senses the repulsive force from the compressed test specimen and records it continuously. The test specimen is compressed at a rate of 1.0 mm / min until it reaches 30% strain, and the relationship between compression force and deflection (compression force-deformation curve) is recorded. From the recorded compression force-deformation curve, the compression force (25% compression force) when the deflection is 25% relative to the thickness of the test specimen before compression is determined. The 25% compression load is calculated using the following formula. 25% compression load [MPa] = 25% compression force [N] / area of ​​test piece [mm ２ ]

[0048] The 25% compression hardness is preferably 0.50 MPa or more, more preferably 1.00 MPa or more, even more preferably 1.50 MPa or more, and may be 2.00 MPa or more, 2.50 MPa or more, 3.00 MPa or more, 3.50 MPa or more, or 4.00 MPa or more. The upper limit of the 25% compression hardness is not particularly limited. Measurement may be stopped when the 25% compression hardness reaches 10 MPa or more. In that case, the upper limit of the 25% compression hardness is set to "10 MPa or more." The upper limit of the 25% compression hardness may be "10 MPa or more," or may be 9.00 MPa or less, 8.00 MPa or less, 7.00 MPa or less, 6.00 MPa or less, or 5.00 MPa or less.

[0049] (3) Tensile Strength Tensile strength can be measured based on JIS K 6251:2010. For example, tensile strength can be measured as follows. A test piece is made into a No. 3 dumbbell shape. The test piece is pulled at a pulling speed of 200 mm / min, and the maximum tensile force [N] until the test piece breaks is measured. The tensile strength is calculated by the following formula: Tensile strength [MPa] = Maximum force [N] / Area of ​​the parallel part of the test piece [mm ２ ]

[0050] The elongation is preferably 75% or more, more preferably 80% or more, even more preferably 90% or more, particularly preferably 100% or more, and may be 105% or more, or 110% or more. The upper limit of the elongation is not particularly limited, and is, for example, 200% or less.

[0051] (4) Elongation Elongation can be measured based on JIS K 6251:2010. For example, elongation can be measured as follows. A test specimen is made into a No. 3 dumbbell shape. The test specimen is pulled at a tensile speed of 200 mm / min, and the gauge length at the time of breaking the test specimen is measured. The elongation (elongation at break) is calculated by the following formula: Elongation at break [%] = ((gauge length at break [mm] - initial gauge length [mm]) / initial gauge length [mm]) × 100

[0052] The elongation is preferably 75% or more, more preferably 80% or more, even more preferably 90% or more, particularly preferably 100% or more, and may be 105% or more, or 110% or more. The upper limit of the elongation is not particularly limited, and is, for example, 200% or less.

[0053] (5) Tear Strength Tear strength can be measured based on JIS 6252:2007. For example, tear strength can be measured as follows. A test specimen is an angle-shaped test specimen without a notch. The test specimen is pulled at a tensile speed of 200 mm / min, and the maximum tensile force [N] until the test specimen breaks is measured. Tear strength is calculated by the following formula: Tear strength [N / mm] = Maximum force [N] / Thickness of test specimen [mm]

[0054] The tear strength is preferably 8 N / mm or more, more preferably 15 N / mm or more, even more preferably 20 N / mm or more, particularly preferably 25 N / mm or more, and may be 30 N / mm or more, 35 N / mm or more, or 40 N / mm or more. The upper limit of the tear strength is not particularly limited, and is, for example, 80 N / mm or less.

[0055] (6) Compression Set (25%) The compression set at 25% compression can be measured based on JIS K 6401:2011. For example, the compression set at 25% compression can be measured as follows. A test specimen is formed into a rectangular column shape measuring 50 mm x 50 mm. A thickness gauge is used for the measurement. The thickness gauge is used to measure the initial thickness [T0] of the test specimen. A compression set jig is used to set spacers of 75% of the initial thickness, the jig is fastened with screws (3 places), and the specimen is left in a constant temperature bath at 70°C for 22 hours. The jig is removed from the constant temperature bath, and the test specimen is taken out. The removed test specimen is left at room temperature for 30 minutes, and then the thickness of the test specimen is measured again [T1]. The compression set at 25% compression is calculated using the following formula: Compression set at 25% compression [%] = ((T0 - T1) / T0) x 100

[0056] The compression set at 25% compression is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, and particularly preferably 2% or less. The lower limit of the compression set is not particularly limited, and is usually 0%.

[0057] (7) Thickness The polyurethane foam may be, for example, in the form of a sheet having a predetermined thickness. The thickness of the polyurethane foam is preferably 10 mm or less, and may be 6 mm or less, 3 mm or less, or 1 mm or less. The thickness of the polyurethane foam is greater than 0 mm.

[0058] The thickness precision of polyurethane foam is preferably 0.5 mm or less, more preferably 0.2 mm or less, and even more preferably 0.05 mm or less. The thickness precision of polyurethane foam is usually 0 mm or more. The thickness precision of polyurethane foam is measured as follows. For a sheet-like polyurethane foam sample of a predetermined thickness, the thickness is measured in a straight line at 25 mm intervals. The thickness is measured at 42 points, and the maximum thickness value [mm] and minimum thickness value [mm] are determined. The thickness precision of polyurethane foam is calculated by the following formula: Thickness precision [mm] = Maximum thickness value [mm] - Minimum thickness value [mm]

[0059] 3. Method for Producing Polyurethane Foam Polyurethane foam is preferably produced by a typical polyurethane foam production method used when employing the mechanical froth method. For example, a polyurethane foam composition is introduced into a mixing head and then stirred and mixed to homogeneity while mixing with an inert gas. The polyurethane foam composition mixed in the mixing head is then heated and cured on release paper or in a predetermined mold to obtain a polyurethane foam. To form foam of the desired density, the amount of inert gas stirred into the composition is controlled by a gas flow meter. Increasing the amount of cell-forming inert gas decreases the density, while decreasing the amount of inert gas increases the density. If necessary, the inert gas may be a gas that is gaseous under ambient conditions and is substantially inert or completely unreactive with any liquid-phase components. Examples include nitrogen, carbon dioxide, and dry air, which is a normally dried gas.

[0060] 4. Uses of Polyurethane Foam Polyurethane foam is suitable as a buffer material. Polyurethane foam is particularly suitable as a buffer material used in semiconductor polishing members. For example, as shown in FIG. 1 , a semiconductor polishing member 10 includes a polishing pad 11 for polishing a semiconductor material 5, a polishing plate 13 for rotating the polishing pad 11, and a buffer material 15 including the polyurethane foam of the present disclosure, which is laminated between the polishing pad 11 and the polishing plate 13. The semiconductor polishing member 10 is suitable for a chemical mechanical polishing (CMP) apparatus 1.

[0061] The chemical mechanical polishing (CMP) apparatus 1 includes a semiconductor polishing member 10, a slurry supply unit 4 that supplies polishing slurry 3 to a polishing pad 11, and a polishing head 6 that presses a semiconductor material 5 against the polishing pad 11. The polishing plate 13 and the polishing head 6 move relative to each other while rotating. The semiconductor material 5 is held by the polishing head 6 and moves together with the polishing head 6. When the polishing plate 13 and the polishing head 6 move relative to each other, the slurry 3 enters between the semiconductor material 5 and the polishing pad 11, and the semiconductor material 5 is polished by the polishing pad 11.

[0062] The buffer material 15 is desired to have sufficient hardness and moderate flexibility to ensure the flatness of the semiconductor material 5. However, it has been difficult to achieve both high hardness and flexibility in polyurethane foams in the past. The polyurethane foam of the present disclosure has sufficient hardness and also ensures flexibility, making it suitable as the buffer material 15.

[0063] The use of polyurethane foam is not limited to the buffer material 15 of the semiconductor polishing member 10. The polyurethane foam of the present disclosure has sufficient hardness and flexibility, and is therefore useful as a buffer material for members other than semiconductor polishing members, and is also useful for applications other than buffer materials. For example, the polyurethane foam of the present disclosure is also suitable for test pieces used as polishing targets in place of the semiconductor material 5. In addition, polyurethane foam is also suitable as a cushioning material for automotive components, for example, a cushioning material for batteries such as lithium-ion batteries.

[0064] Hereinafter, a more specific explanation will be given using examples. 1. Preparation of polyurethane foam Compositions of Example 1, Example 2-1, Example 2-2, Example 2-3, Example 3-1, Example 3-2, Example 3-3, Example 4-1, Example 4-2, Example 4-3, Example 5, and Comparative Example 1 were prepared using the blending ratios shown in Tables 1 to 3. In Tables 1 to 3, the blending ratio of each component represents the blending ratio (parts by mass) relative to the total amount of polyol (including resin modifier) ​​shown in the "Total of polyols" column.

[0065] The prepared composition was mixed with a foam-forming gas (nitrogen) in a mechanical froth foaming machine, stirred, and continuously discharged onto a release paper to produce a sheet-like polyurethane foam with a thickness of 2 mm. The mixing ratio of the foam-forming gas (nitrogen) was adjusted so that the density of the polyurethane foam was 300 kg / m. ３ -700 kg / m ３ In order to confirm the thickness accuracy, sheets of polyurethane foam having a thickness of 0.8 mm and a thickness of 2.47 mm were also prepared for Example 3-3.

[0066] Details of the raw materials for the polyurethane foams in Tables 1 to 3 are shown below. Polymer polyol 1... Polymer polyol, product name: FS-7301 (manufactured by Sanyo Chemical Industries, Ltd.), resin content: 43.0%, hydroxyl value: 33.5 mg KOH / g, number of functional groups: 3, number average molecular weight: 3000 Polymer polyol 2... Polymer polyol, product name: EX-914 (manufactured by AGC), resin content: 22.9%, hydroxyl value: 42.0 mg KOH / g, number of functional groups: 3, number average molecular weight: 3000 Polymer polyol 3... Polymer polyol, product name: EX-913 (manufactured by AGC), resin content: 20.0%, hydroxyl value: 28.6 mg KOH / g, number of functional groups: 2, number average molecular weight: 3000 Polyester polyol 1... Polycaprolactone-based polyester polyol, product name: Y-6555 (manufactured by ADEKA Corporation), resin content: 0%, hydroxyl value: 212.0 mg KOH / g, number of functional groups: 2, number average molecular weight: 529 Polyester polyol 2... Adipate-based polyester polyol, product name: PCL-205 (manufactured by Daicel Corporation), resin content: 0%, hydroxyl value: 212.0 mg KOH / g, number of functional groups: 2, number average molecular weight: 529 Low molecular weight polyol 1... Dipropylene glycol (manufactured by AGC Corporation), resin content: 0%, hydroxyl value: 837 mg KOH / g, number of functional groups: 2, molecular weight: 134 Low molecular weight polyol 2... Glycerin (manufactured by Lion Specialty Chemicals Corporation), resin content: 0%, hydroxyl value: 837 mg KOH / g, number of functional groups: 2, molecular weight: 134 Resin modifier...polymer particle dispersion, MBS resin / polypropylene glycol (molecular weight 400) = 40 / 60 weight ratio, product name: MX-714 (Kaneka Corporation), hydroxyl value: 171.0 mg KOH / g, number of functional groups: 2, number average molecular weight: 400 Filler...aluminum hydroxide, product name: C-31 (Sumitomo Chemical Co., Ltd.) Foam stabilizer...silicone-based foam stabilizer, product name: SZ-1952 (Dow-Toray Industries, Inc.), hydroxyl value: 40.0 mg KOH / g, number of functional groups: 1, number average molecular weight: 1400 Catalyst 1...iron catalyst, product name: FIN-P1 (Nippon Chemical Industry Co., Ltd.), hydroxyl value: 56.1 mg KOH / g, number of functional groups: 2, number average molecular weight: 2000 Catalyst 2...nickel catalyst, product name: Pat-cat 7001 (Patcham), hydroxyl value: 56.1 mg KOH / g, number of functional groups: 2, number average molecular weight: 2000Antioxidant...hindered phenol-based antioxidant, product name: IRGANOX 1135 (manufactured by BASF Japan Ltd.) Moisture absorbent...zeolite, product name: molecular sieve 3A POWDER (manufactured by Union Showa Co., Ltd.) Isocyanate 1...polymeric MDI (crude MDI), product name: Lupranate M5S (manufactured by BASF INOAC Polyurethanes Co., Ltd.), NCO%: 31.5, number of functional groups: 2.4, number average molecular weight: 320 Isocyanate 2...urethane-modified MDI (urethane-modified polymeric MDI), product name: Foamrite 3700B (manufactured by BASF INOAC Polyurethanes Co., Ltd.), NCO%: 25.0, number of functional groups: 2.12, number average molecular weight: 336 Isocyanate 3...MDI, product number: MTL-S (manufactured by Tosoh Corporation) , NCO%: 30.9, number of functional groups: 2.15, number average molecular weight: 292

[0067]

[0068]

[0069]

[0070] 2. Evaluation method (1) Density (apparent density) Density (kg / m ３ ) was measured as apparent density based on JIS K6401:2011. The measurement results are shown in Tables 1 to 3. (2) 25% Compression Hardness (CLD) The 25% compression hardness was measured by measuring the 25% compression load (MPa) at 25°C using the method described in the embodiment. The measurement results are shown in Tables 1 to 3. (3) Tensile Strength, Elongation, and Tear Strength The tensile strength, elongation, and tear strength were measured by measuring the tensile strength (MPa), elongation (%), and tear strength (N / mm) at 25°C using the method described in the embodiment. The measurement results are shown in Tables 1 to 3. (4) Compression Set (25%) The compression set (%) at 25% compression was measured using the method described in the embodiment. The measurement results are shown in Tables 1 to 3.

[0071] (5) 180-Degree Bending A rectangular test piece measuring 50 mm x 200 mm was obtained from a 2 mm thick sheet of polyurethane foam from each Example and Comparative Example. The tester placed the test piece on a flat surface, folded the test piece 180 degrees in the long direction so that it was half its size, and pressed the fold with his / her hand. The test piece after folding was visually observed and evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 3. Good: No cracks occurred in the test piece. Fair: No noticeable cracks occurred in the test piece, but small cracks were observed. Poor: Noticeable cracks were observed in the test piece.

[0072] (6) Thickness Accuracy The thickness accuracy was measured for the 0.8 mm and 2.47 mm thick sheet-shaped polyurethane foam samples of Example 3-3 by the method described in the embodiment. The thickness accuracy of the 0.8 mm thick sample was 0.018 mm. The thickness accuracy of the 2.47 mm thick sample was 0.197 mm.

[0073] 3. Results Each example satisfies the following requirements (a) to (d). Comparative Example 1 does not satisfy the following requirement (d). Requirement (a): A polyurethane foam obtained from a composition containing a polyol and an isocyanate. Requirement (b): The polyol contains a polymer polyol. Requirement (c): The polyol contains a polyester polyol having a number average molecular weight of more than 250. Requirement (d): The polyol contains a polyol having a number average molecular weight or molecular weight of 250 or less, and the content of the polyol having a number average molecular weight or molecular weight of 250 or less is 15 parts by mass or more when the total amount of polyol is 100 parts by mass.

[0074] The 25% compression hardness of each Example (except for Example 5, which was not measured) was 1.37 MPa or more. In contrast, the 25% compression hardness of Comparative Example 1 was 0.39 MPa. The elongation of each Example (except for Example 5, which was not measured) was 80% to 120%. Furthermore, each Example (except for Example 5, which was not measured) also had good physical properties other than elongation. Each Example had good moldability. Example 3-3 had good thickness precision.

[0075] According to the above examples, polyurethane foams having sufficient hardness while ensuring flexibility could be provided.

[0076] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible.

[0077] 1: Chemical mechanical polishing (CMP) device 3: Slurry 4: Slurry supply unit 5: Object to be polished 6: Polishing head 10: Semiconductor polishing member 11: Polishing pad 13: Polishing plate 15: Cushioning material

Claims

1. A polyurethane foam obtained from a composition containing a polyol and an isocyanate, The polyol is a polymer polyol; a polyester polyol having a number average molecular weight of more than 250; a polyol having a number average molecular weight or molecular weight of 250 or less, A polyurethane foam, wherein the content of the polyol having a number average molecular weight or a molecular weight of 250 or less is 15 parts by mass or more, based on 100 parts by mass of the total amount of the polyol.

2. 2. The polyurethane foam according to claim 1, wherein the polyol having a number average molecular weight or molecular weight of 250 or less comprises a polyol having a functionality greater than 2.

3. 3. The polyurethane foam according to claim 1, wherein the isocyanate comprises urethane-modified MDI.

4. A cushioning material comprising the polyurethane foam according to claim 1 or 2.

5. 5. A semiconductor polishing member comprising: a polishing pad for polishing a semiconductor material; a polishing plate for rotating said polishing pad; and the buffer material according to claim 4 laminated between said polishing pad and said polishing plate.