Urethane composition, cured product, impact-resistant adhesive, and power semiconductor sealing agent

Abstract

The purpose of the present disclosure is to provide a urethane composition capable of forming a cured product having exceptional tensile strength and elongation while having adequate impact resistance. A urethane composition according to the present disclosure is characterized by containing an ester-based polyol and a polyisocyanate, the ester-based polyol including a structure derived from an alicyclic diol compound, and no crystal melting peak being confirmed by DSC analysis. The polyisocyanate is preferably a non-aromatic isocyanate, and the polyisocyanate preferably contains a bifunctional isocyanate and a trifunctional isocyanate.

Description

Urethane composition, cured product, impact-resistant adhesive, and power semiconductor sealant

[0001] This disclosure relates to a urethane composition, a cured product, an impact-resistant adhesive, and a power semiconductor encapsulant. This application claims priority from Japanese Patent Application No. 2023-138986, filed on August 29, 2023, the contents of which are incorporated herein by reference.

[0002] A thermally conductive resin that is flexible enough to conform to the shape of a heat-generating element and adhere to it is used as a method for dissipating (radiating) heat generated by electronic components, etc. A urethane-based composition containing a specific ester polyol, a polyisocyanate, and a filler is known to be used as a thermally conductive resin that has excellent heat dissipation properties and adhesion to a heat-generating element (see, for example, Patent Document 1).

[0003] It is also known that when electronic components are used in large devices such as automobiles, they are required to have excellent shock resistance in order to cope with external stimuli such as vibrations.

[0004] Japanese Patent Application Laid-Open No. 2020-533467

[0005] However, the invention of the urethane-based composition described in Patent Document 1 has the problem that the ester-based polyol and polyisocyanate used tend to crystallize, and the cured product tends to be too hard, resulting in poor impact resistance.

[0006] Furthermore, in order to solve the above problems, it is necessary to use a large amount of polyisocyanate having a specific structure, but in this case, it has been known that the strength and elongation of the resin tend to deteriorate.

[0007] Therefore, an object of the present disclosure is to provide a urethane composition that can form a cured product that has sufficient impact resistance while also having excellent tensile strength and elongation.

[0008] As a result of earnest efforts to solve the above problems, the present inventors have discovered that a urethane composition containing an ester polyol and a polyisocyanate, in which the ester polyol contains a specific structural moiety and in which no crystalline melting peak is confirmed by DSC analysis, can form a cured product that has sufficient impact resistance while also having excellent tensile strength and elongation. The present disclosure relates to a product that has been completed based on these findings.

[0009] That is, the present disclosure provides a urethane composition comprising an ester-based polyol and a polyisocyanate, wherein the ester-based polyol contains a structural moiety derived from an alicyclic diol compound, and in which no crystalline melting peak is confirmed by DSC analysis.

[0010] The urethane composition exhibits excellent impact resistance because it is not subject to excessive curing due to crystallization, and the ester polyol contains a structural unit derived from an alicyclic diol compound, resulting in a cured product with excellent tensile strength and elongation.

[0011] The polyisocyanate is preferably a non-aromatic polyisocyanate, since the non-aromatic isocyanate is easy to handle.

[0012] The polyisocyanate preferably contains a difunctional isocyanate and a trifunctional isocyanate. This configuration can suppress crystallization of the urethane composition, making it easier for the cured product to exhibit impact resistance.

[0013] The content of the trifunctional isocyanate in the polyisocyanate is preferably less than 45%. By having this configuration, the tensile strength and elongation of the cured product can be easily improved.

[0014] The polyisocyanate preferably includes hexamethylene diisocyanate and hexamethylene diisocyanate trimer.

[0015] The ester polyol is preferably a polycaprolactone polyol having a number average molecular weight of 400 to 800. By having the above-mentioned structure, the crystallinity of the urethane composition can be reduced, making it easier for the cured product to exhibit impact resistance.

[0016] The alicyclic diol compound preferably contains 1,4-cyclohexanedimethanol.

[0017] The urethane composition is preferably a two-component type.

[0018] The present disclosure also provides a cured product of the urethane composition.

[0019] The present disclosure also provides an impact-resistant adhesive comprising the above-mentioned cured product.

[0020] The present disclosure also provides a power semiconductor encapsulant containing the cured product.

[0021] The urethane composition of the present disclosure can form a cured product that has sufficient impact resistance while also having excellent tensile strength and elongation.

[0022] [Urethane Composition] A urethane composition according to one embodiment of the present disclosure (hereinafter, may be referred to as the “urethane composition of the present disclosure”) comprises an ester polyol and a polyisocyanate, wherein the ester polyol comprises a structural moiety derived from an alicyclic diol compound, and no crystalline melting peak is confirmed by DSC analysis.

[0023] The urethane composition of the present disclosure does not exhibit a crystalline melting peak in DSC analysis, making it less likely to undergo excessive curing due to crystallization and enabling it to exhibit impact resistance. Furthermore, the inclusion of a structural moiety derived from an alicyclic diol compound in the ester-based polyol allows the cured product to have excellent tensile strength and elongation.

[0024] The viscosity of the urethane composition of the present disclosure at 25°C is preferably 20,000 mPa·s or less, more preferably 10,000 mPa·s or less, even more preferably 1,000 mPa·s or less, particularly preferably 500 mPa·s or less, or even 300 mPa·s or less. A viscosity of 20,000 mPa·s or less allows the composition to exhibit sufficient fluidity in a liquid state and provide excellent handleability. The lower limit is not particularly limited, but is preferably 10 mPa·s or more, more preferably 50 mPa·s or more. The viscosity is measured using an E-type viscometer, and when the urethane composition contains a filler, it is measured using a rheometer.

[0025] (Ester-based polyol) The urethane composition of the present disclosure contains an ester-based polyol, and the ester-based polyol contains a structural moiety derived from an alicyclic diol compound. The urethane composition is less likely to crystallize with polyisocyanate because the ester-based polyol contains a structural moiety derived from an alicyclic diol compound. This makes it possible to reduce the amount of polyisocyanate (described below) blended, resulting in a cured product with excellent tensile strength and elongation. In the present disclosure, "ester-based polyol" refers to a compound in which two or more monomer units containing ester bonds in the molecule are polymerized and have two or more hydroxyl groups. The urethane composition of the present disclosure may contain only one type of ester-based polyol, or two or more types.

[0026] Examples of the ester polyol include carboxylic acid polyols, which are condensation polymers of polyhydric alcohols and polycarboxylic acids, and lactone polyols, which are ring-opening polymers of cyclic esters (lactones). Among these, the ester polyol is preferably a lactone polyol derived from a lactone using the alicyclic diol compound as an initiator. More specifically, the ester polyol is preferably one obtained by ring-opening polymerization of lactones using the alicyclic diol compound as an initiator.

[0027] Examples of the alicyclic diol compound include cyclohexanediols such as 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol, cyclohexanedimethanols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol, norbornanedimethanols such as 2,3-norbornanedimethanol and 2,5-norbornanedimethanol, tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalindimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide, with cyclohexanedimethanols being preferred, and 1,4-cyclohexanedimethanol being particularly preferred. Note that the alicyclic diol compound may be used alone or in combination of two or more.

[0028] Specific examples of the lactones include β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, δ-caprolactone, ε-caprolactone, γ-valerolactone, γ-caprolactone, γ-caprylolactone, γ-laurolactone, enantholactone, dodecanolactone, stearolactone, alkyl-ε-caprolactone [for example, monomethyl-ε-caprolactone (α-methyl-ε-caprolactone, β-methyl- Examples of suitable lactones include lactones having 4 to 20 carbon atoms (preferably lactones having 4 to 15 carbon atoms, more preferably lactones having 4 to 10 carbon atoms), such as methyl-ε-caprolactones such as ε-caprolactone, γ-methyl-ε-caprolactone, dimethyl-ε-caprolactone (β,δ-dimethyl-ε-caprolactone), and trimethyl-ε-caprolactone (3,3,5-trimethyl-ε-caprolactone), and ε-caprolactone is preferred. That is, the lactone polyol of the present disclosure is preferably a polycaprolactone polyol. Note that only one type of lactone may be used, or two or more types may be used.

[0029] The number average molecular weight of the ester polyol is not particularly limited, but is preferably 400 to 800, more preferably 450 to 750, and even more preferably 500 to 700. When the number average molecular weight of the ester polyol is within the above range, excellent handleability can be achieved.

[0030] The ester polyol is preferably liquid at any one of room temperatures. In the present disclosure, "room temperature" means 20 to 30°C.

[0031] (Polyisocyanate) The urethane composition of the present disclosure contains a polyisocyanate. The polyisocyanate acts as a curable component in the urethane composition of the present disclosure. In the urethane composition of the present disclosure, only one type of polyisocyanate may be used, or two or more types may be used. In this disclosure, "polyisocyanate" refers to a compound having two or more isocyanate groups (i.e., bifunctional or higher).

[0032] From the viewpoint of ease of handling, the polyisocyanate is preferably a non-aromatic polyisocyanate, more preferably an aliphatic polyisocyanate or an alicyclic polyisocyanate, and particularly preferably an aliphatic polyisocyanate.

[0033] Furthermore, from the viewpoint of reducing the crystallinity of the urethane composition, the polyisocyanate preferably contains a tri- or higher functional isocyanate, and from the viewpoint of exhibiting tensile strength and elongation of the cured product, it is more preferable that the polyisocyanate contains a bifunctional isocyanate and a tri- or higher functional isocyanate, and it is particularly preferable that the polyisocyanate contains a bifunctional isocyanate and a trifunctional isocyanate.

[0034] Specific examples of the bifunctional isocyanate include aliphatic polyisocyanates such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and decamethylene diisocyanate; and alicyclic polyisocyanates such as 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, 1,4-bis(isocyanatemethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornene diisocyanate.

[0035] Examples of the tri- or higher functional isocyanates include oligomers of the compounds exemplified as the bifunctional isocyanates, and trimers of the bifunctional isocyanates are particularly preferred.

[0036] The urethane composition of the present disclosure preferably contains hexamethylene diisocyanate and hexamethylene diisocyanate trimer.

[0037] Furthermore, when the polyisocyanate contains a trifunctional isocyanate, the blending amount thereof is preferably less than 45% by mass, more preferably 40% by mass or less, and even more preferably 35% by mass or less, of the total amount of polyisocyanate (100% by mass). A blending amount of trifunctional isocyanate of less than 45% by mass makes it easier for the cured product to exhibit sufficient tensile strength and elongation. Furthermore, since trifunctional isocyanates are usually expensive, costs can also be reduced. The lower limit is preferably 5% by mass or more, more preferably 10% by mass or more. A blending amount of 5% by mass or more makes it easier to suppress crystallization of the urethane composition.

[0038] In the urethane composition of the present disclosure, the ratio of the number of moles of isocyanate groups in the polyisocyanate to the number of moles of hydroxyl groups in the ester polyol [NCO / hydroxyl] is preferably in the range of 0.8 to 1.5, more preferably 0.85 to 1.4, and even more preferably 0.9 to 1.3. That is, in the urethane composition of the present disclosure, the ratio of the number of moles of structural units derived from isocyanate groups to the number of moles of structural units derived from hydroxyl groups other than those forming ester bonds in the ester polyol is preferably within the above range.

[0039] The urethane composition of the present disclosure preferably contains a catalyst to promote the reaction between the ester polyol and the polyisocyanate. Known or conventional catalysts can be used as the catalyst, including amine catalysts, imidazole catalysts, and metal catalysts. Only one type of catalyst may be used, or two or more types may be used.

[0040] Examples of the amine catalyst include triethylenediamine, 2-methyltriethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylpropylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, N,N,N',N",N"-pentamethyl-(3-aminopropyl)ethylenediamine, N,N,N',N",N"-pentamethyldipropylenetriamine, N,N,N',N"-tetramethylhexamethylenediamine, and bis(2-dimethylaminoethyl)ether.

[0041] Examples of the imidazole catalyst include 1-methylimidazole, 1,2-dimethylimidazole, 1-isobutyl-2-methylimidazole, and 1-dimethylaminopropylimidazole.

[0042] Examples of the metal catalyst include organotin catalysts such as stannous diacetate, stannous dioctoate, stannous dioleate, stannous dilaurate, dibutyltin oxide, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, and dioctyltin dilaurate.

[0043] The amount of the catalyst blended is preferably 0.001 to 0.05 parts by mass, and more preferably 0.005 to 0.03 parts by mass, relative to the total amount (100 parts by mass) of the resin components in the urethane composition.

[0044] The urethane composition of the present disclosure may also contain a filler to ensure sufficient heat dissipation when cured. Only one type of filler may be used, or two or more types may be used.

[0045] As the filler, known or commonly used fillers can be used, such as metal fillers, carbon fillers, and metal oxide fillers. Examples of metal fillers include metal fillers made of gold, silver, copper, nickel, palladium, tin, aluminum, or alloys thereof. The metal filler may be made of a single metal, or may be made of two or more metals, such as a core-shell structure.

[0046] The shape of the filler may be spherical, irregular, flake (flat), needle-like, fibrous, rod-like, etc. The average particle size (median size) is preferably 1 nm to 100 μm, more preferably 10 nm to 50 μm, even more preferably 30 nm to 35 μm, and particularly preferably 50 nm to 10 μm.

[0047] When the filler is contained, the blending amount is preferably 50 to 95% by mass, more preferably 60 to 90% by mass, based on the total amount (100% by mass) of the urethane composition. By being in this range, heat dissipation properties can be easily exhibited.

[0048] (Other Components) The urethane composition of the present disclosure may contain other components in addition to the ester polyol, polyisocyanate, catalyst, and filler. Examples of the other components include polyols other than the ester polyols, light stabilizers, UV absorbers, antioxidants, solvents, flame retardants, pigments, antimicrobial agents, antistatic agents, processing aids, and viscosity improvers. The content of the other compounds is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass, relative to the total amount (100% by mass) of the urethane composition of the present disclosure.

[0049] Furthermore, of the total amount (100% by mass) of polyols contained in the urethane composition of the present disclosure, the amount of the ester polyol is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0050] The urethane composition of the present disclosure can be prepared by mixing the above-described components by a known or conventional method. In particular, the urethane composition of the present disclosure is preferably a two-component urethane composition containing the above-described ester polyol as a base component and the above-described polyisocyanate as a curing agent.

[0051] (Cured Product) A cured product of the urethane composition can be produced by curing the urethane composition of the present disclosure by a known or conventional method. In particular, when the urethane composition of the present disclosure is a two-component urethane composition, it may be cured by heating or at room temperature. When curing by heating, the heating temperature is preferably 25 to 150°C. The curing time may be 0.5 to 20 hours.

[0052] The cured product preferably has an A hardness of 50 to 69, more preferably 55 to 68, and even more preferably 60 to 67, when measured at a thickness of 6 mm or more. Having an A hardness of 69 or less makes it easier for the cured product to exhibit impact resistance. Also, having an A hardness of 50 or more can prevent the cured product from being too soft and breaking.

[0053] The cured product preferably has a tensile strength at break of 18 MPa or more, more preferably 20 MPa or more, and even more preferably 22 MPa or more, as measured using a No. 3 dumbbell at a pulling speed of 500 mm / min and a chuck distance of 60 mm. A tensile strength of 18 MPa or more ensures sufficient strength. There is no particular upper limit, but a value of 50 MPa or less is preferred.

[0054] Furthermore, the elongation at break measured under the same conditions as the tensile strength is preferably 300% or more, more preferably 350% or more, and even more preferably 400% or more. By having the elongation be 300% or more, the elongation of the cured product can be made sufficient. Furthermore, although there is no particular upper limit, it is preferably 600% or less.

[0055] The cured product preferably has a shear adhesive strength of 3.6 MPa or more, more preferably 3.8 MPa or more, and even more preferably 4.0 MPa or more, measured on a test piece prepared by bonding two Al substrates together at a test speed of 5 mm / min and a chuck distance of 112.5 mm according to JIS K 6850. The upper limit is not particularly limited, but is preferably 10 MPa or less.

[0056] The cured product preferably has a shear adhesive strength of 2.0 MPa or more, more preferably 2.5 MPa or more, measured on a test piece prepared by laminating an Al substrate and a PET substrate at a test speed of 5 mm / min and a chuck distance of 112.5 mm according to JIS K 6850. The upper limit is not particularly limited, but is preferably 10 MPa or less.

[0057] The cured product is cured under the conditions of the examples described below, and when heated at a temperature controlled rate of 10°C / min using a differential scanning calorimeter, no crystalline melting peak is observed. The absence of a crystalline melting peak prevents excessive curing when the product is cured, allowing the product to exhibit impact resistance.

[0058] The cured product has sufficient impact resistance and excellent tensile strength and elongation, and therefore can be used as an impact-resistant adhesive, and is particularly suitable as an impact-resistant adhesive for use in large devices that are subject to large vibrations, such as automobiles and aircraft. Furthermore, the cured product has heat dissipation properties, and therefore can be suitably used as an encapsulant for power semiconductors that have high output and generate a large amount of heat.

[0059] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, each configuration and combination thereof in each embodiment is merely an example, and additions, omissions, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the claims.

[0060] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0061] Example 1 128.21 g of 1,4-cyclohexanedimethanol-modified polycaprolactone diol (Mw: 530), 36.19 g of HDI (trade name "HDI", manufactured by Tosoh Corporation), 15.61 g of HDI trimer (trade name "Duranate TKA-100", manufactured by Asahi Kasei Corporation) (HDI trimer content 30% by mass), and 0.018 g of dibutyltin dilaurate (DBTDL) were weighed into a stirring cup, and the mixture was vacuum degassed and stirred for 60 seconds using a vacuum degassing mixer (trade name "Vacuum Foam Mixer", manufactured by Thinky Corporation) to produce the urethane composition of Example 1. The urethane composition was then cast into a casting mold prepared by sandwiching a silicone spacer between glass plates. After casting, the composition was cured for 16 hours or more in a gear oven set at 30°C, and after curing, it was released from the glass mold and then aged for 2 days or more to obtain a cured product. The thickness of the cured product was 2 mm.

[0062] Example 2 124.45 g of 1,4-cyclohexanedimethanol-modified polycaprolactone diol (Mw: 530), 30.76 g of HDI (trade name "HDI", manufactured by Tosoh Corporation), 24.79 g of HDI trimer (trade name "Duranate TKA-100", manufactured by Asahi Kasei Corporation) (HDI trimer content 45% by mass), and 0.018 g of dibutyltin dilaurate (DBTDL) were weighed into a stirring cup, and the mixture was vacuum degassed and stirred for 60 seconds using a vacuum degassing mixer (trade name "Vacuum Foam Mixer", manufactured by Thinky Corporation) to produce a urethane composition of Example 2. A cured product of Example 2 was also produced in the same manner as in Example 1.

[0063] Comparative Example 1 113.75 g of 1,4-BG-modified polycaprolactone diol (Mw: approximately 400), 36.69 g of HDI (trade name "HDI", manufactured by Tosoh Corporation), 29.57 g of HDI trimer (trade name "Duranate TKA-100", manufactured by Asahi Kasei Corporation) (HDI trimer content 45% by mass), and 0.018 g of dibutyltin dilaurate (DBTDL) were weighed into a stirring cup, and the mixture was vacuum degassed and stirred for 60 seconds using a vacuum degassing mixer (trade name "Vacuum Foam Mixer", manufactured by Thinky Corporation) to produce a urethane composition of Comparative Example 1. A cured product of Comparative Example 1 was also produced in the same manner as in Example 1.

[0064] Comparative Example 2 117.87 g of 1,4-BG-modified polycaprolactone diol (Mw: approximately 400), 43.41 g of HDI (trade name "HDI", manufactured by Tosoh Corporation), 18.72 g of HDI trimer (trade name "Duranate TKA-100", manufactured by Asahi Kasei Corporation) (HDI trimer content 30% by mass), and 0.018 g of dibutyltin dilaurate (DBTDL) were weighed into a stirring cup, and the mixture was vacuum degassed and stirred for 60 seconds using a vacuum degassing mixer (trade name "Vacuum Foam Mixer", manufactured by Thinky Corporation) to produce a urethane composition of Comparative Example 2. A cured product of Comparative Example 2 was also produced in the same manner as in Example 1.

[0065] [Evaluation] The urethane compositions and their cured products obtained in the Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1.

[0066] (1) Viscosity The viscosity at 25° C. of the urethane compositions of the Examples and Comparative Examples was measured using an E-type viscometer.

[0067] (2) A Hardness Three sheets of the cured products of the Examples and Comparative Examples were stacked together to a thickness of 6 mm or more, and the A hardness was measured using a durometer (product name "GS-610", manufactured by Teclock Corporation).

[0068] (3) Tensile Strength and Elongation No. 3 dumbbell test pieces were cut out from the cured products of the Examples and Comparative Examples using a dumbbell cutter, and a tensile test was carried out using a tensile tester (product name "RTC-1350A", manufactured by A&D Co., Ltd.) at a pulling speed of 500 mm / min and a chuck distance of 60 mm, to measure the tensile strength and elongation at the time when the cured product broke.

[0069] (4) Shear Adhesion Strength The urethane compositions of the Examples and Comparative Examples were spread on an Al substrate or a PET substrate based on the test piece dimensions specified in JIS K 6850, and the Al substrates were bonded to each other or to a PET substrate. The test pieces were cured in a Geer oven at 30°C for 16 hours or more to obtain test pieces. The tensile shear adhesive strength of the obtained test pieces was measured using a tensile tester (product name "RTC-1350A", manufactured by A&D Co., Ltd.) at a test speed of 5 mm / min and a chuck distance of 112.5 mm.

[0070] (5) Presence or absence of crystalline melting peak The cured products of the examples and comparative examples were heated at a temperature controlled rate of 10°C / min using a differential scanning calorimeter (trade name "DSC Q-2000", manufactured by TA Instruments Co., Ltd.) to measure the presence or absence of a crystalline melting peak of the crystalline component.

[0071]

[0072] In the urethane compositions of the examples, since the ester polyol contains a structural unit derived from an alicyclic diol, the amount of polyisocyanate added can be reduced, and the cured product has excellent tensile strength and elongation. Furthermore, since no crystalline melting peak was observed in DSC analysis, it was confirmed that the composition has impact resistance. On the other hand, when the ester polyol does not contain a structural unit derived from an alicyclic diol, a large amount of polyisocyanate is required to suppress hardness, suggesting that the cured product has poor tensile strength and elongation (Comparative Example 1). Furthermore, when a crystalline melting peak is observed, the hardness increases, suggesting that the impact resistance is poor (Comparative Example 2).

[0073] Variations of the present disclosure are described below. [Appendix 1] A urethane composition comprising an ester polyol and a polyisocyanate, wherein the ester polyol comprises a structural moiety derived from an alicyclic diol compound, and wherein no crystalline melting peak is confirmed by DSC analysis. [Appendix 2] The urethane composition according to Appendices 1, having a viscosity of 20,000 mPa·s or less at 25°C. [Appendix 3] The urethane composition according to Appendices 1 or 2, having a viscosity of 10 mPa·s or more at 25°C. [Appendix 4] The urethane composition according to any one of Appendices 1 to 3, wherein the polyisocyanate is a non-aromatic polyisocyanate. [Appendix 5] The urethane composition according to any one of Appendices 1 to 4, wherein the polyisocyanate comprises a difunctional isocyanate and a trifunctional isocyanate. [Appendix 6] The urethane composition according to Appendices 5, wherein the blending amount of the trifunctional isocyanate in the polyisocyanate is less than 45 mass%. [Appendix 7] The urethane composition according to any one of Appendices 1 to 6, wherein the polyisocyanate comprises hexamethylene diisocyanate and hexamethylene diisocyanate trimer. [Appendix 8] The urethane composition according to any one of Appendices 1 to 7, wherein the ester-based polyol is a polycaprolactone polyol having a number average molecular weight of 400 to 800. [Appendix 9] The urethane composition according to any one of Appendices 1 to 8, wherein the alicyclic diol compound comprises 1,4-cyclohexanedimethanol. [Appendix 10] The urethane composition according to any one of Appendices 1 to 9, wherein the urethane composition comprises a catalyst. [Appendix 11] The urethane composition according to any one of Appendices 1 to 10, wherein the urethane composition comprises a filler. [Appendix 12] The urethane composition according to any one of Appendices 1 to 11, which is a two-component type. [Appendix 13] A cured product of the urethane composition according to any one of Appendices 1 to 12. [Appendix 14] The cured product according to Appendix 13, which has an A hardness of 50 to 69 when measured at a thickness of 6 mm or more. [Appendix 15] The cured product according to Appendix 13 or 14, which has a tensile strength at break of 18 MPa or more when measured using a No. 3 dumbbell at a pulling rate of 500 mm / min and a chuck distance of 60 mm.[Appendix 16] The cured product according to any one of Appendices 13 to 15, having an elongation at break of 300% or more when measured using a No. 3 dumbbell at a tensile speed of 500 mm / min and a chuck distance of 60 mm. [Appendix 17] The cured product according to any one of Appendices 13 to 16, having a shear adhesive strength of 3.6 MPa or more when measured in accordance with JIS K 6850 on a test piece prepared by bonding two Al substrates together at a test speed of 5 mm / min and a chuck distance of 112.5 mm. [Appendix 18] The cured product according to any one of Appendices 13 to 17, having a shear adhesive strength of 2.0 MPa or more when measured in accordance with JIS K 6850 on a test piece prepared by bonding an Al substrate and a PET substrate together at a test speed of 5 mm / min and a chuck distance of 112.5 mm. [Appendix 19] An impact-resistant adhesive comprising the cured product according to any one of Appendices 13 to 18. [Appendix 20] A power semiconductor encapsulant comprising the cured product according to any one of Appendices 13 to 18.

Claims

1. A urethane composition comprising an ester polyol and a polyisocyanate, wherein the ester polyol comprises a structural portion derived from an alicyclic diol compound, and wherein no crystalline melting peak is observed by DSC analysis.

2. The urethane composition according to claim 1, wherein said polyisocyanate is a non-aromatic polyisocyanate.

3. The urethane composition according to claim 1 or 2, wherein the polyisocyanate includes a difunctional isocyanate and a trifunctional isocyanate.

4. The urethane composition according to claim 3, wherein the amount of trifunctional isocyanate in the polyisocyanate is less than 45% by mass.

5. The urethane composition according to claim 1 or 2, wherein the polyisocyanate includes hexamethylene diisocyanate and hexamethylene diisocyanate trimer.

6. The urethane composition according to claim 1 or 2, wherein the ester-based polyol is a polycaprolactone polyol having a number average molecular weight of 400 to 800.

7. The urethane composition according to claim 1 or 2, which contains 1,4-cyclohexanedimethanol as the alicyclic diol compound.

8. The urethane composition according to claim 1 or 2, which is of a two-component type.

9. A cured product of the urethane composition according to claim 1 or 2.

10. An impact resistant adhesive comprising the cured product according to claim 9.

11. A power semiconductor encapsulant comprising the cured product according to claim 9.

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