Urethane resin-forming composition, adhesive agent, cured product, and production method for cured product

Abstract

This urethane resin-forming composition contains a base agent (A) and a curing agent (B). The base agent (A) includes an isocyanate-terminated prepolymer (A-1) that is the reaction product of a component (a) containing: one or more polyol (a-1) selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2); and a polyisocyanate (a-2). The curing agent (B) includes an alicyclic diol (B-1). The urethane resin formation agent forms a urethane resin having a urethane group concentration of at least 2800 mmol / kg.

Description

Urethane resin-forming composition, adhesive, cured product, and method for producing the cured product

[0001] The present disclosure relates to a urethane resin-forming composition, an adhesive, a cured product, and a method for producing the cured product.

[0002] Automotive structural adhesives are required to have a variety of properties, and one property that has attracted particular attention is stability over the operating temperature range.

[0003] The operating temperature range is the temperature range in which an automobile is actually used, specifically, from -30° C. to 80° C. If the physical properties change significantly within this temperature range, the rate at which the adhesive properties change significantly depending on the operating environment will lead to problems such as low reliability.

[0004] Patent Document 1 discloses a urethane adhesive composition comprising a first liquid containing a prepolymer obtained by reacting a polyisocyanate with a polyol of a specific molecular weight and a specific amount of filler, and a second liquid containing a polyol of a specific molecular weight and a catalyst, wherein the number of moles of hydroxyl groups derived from the polyol in the first liquid and the polyol in the second liquid have a specific relationship. According to Patent Document 1, this urethane adhesive composition exhibits good adhesive performance and also has excellent storage stability.

[0005] International Publication No. 2009 / 047962

[0006] Patent Document 1 does not describe the stability of physical properties in the temperature range of use. Patent Document 1 does mention heat resistance durability. However, Patent Document 1 simply evaluates heat resistance durability by leaving the product in an environment at 80°C for 20 days and then returning it to room temperature, based on the tensile shear strength.

[0007] The urethane adhesive composition of Patent Document 1 does not have sufficient stability of physical properties within a usage temperature range (e.g., −30°C to 80°C), particularly in suppressing changes in elastic modulus within a usage temperature range (e.g., −30°C to 80°C), and further improvement is required for practical use.

[0008] Therefore, one aspect of the present disclosure is directed to providing a urethane resin-forming composition and adhesive capable of forming a cured product in which change in elastic modulus is suppressed over a wide temperature range. Another aspect of the present disclosure is directed to providing a cured product in which change in elastic modulus is suppressed over a wide temperature range, and a method for producing the same.

[0009] Each aspect of the present disclosure includes the following embodiments. (1) A urethane resin-forming composition comprising a main component (A) and a curing agent (B), wherein the main component (A) comprises an isocyanate-terminated prepolymer (A-1) that is a reaction product of a component (a) containing one or more polyols (a-1) selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2) and a polyisocyanate (a-2), and the curing agent (B) comprises an alicyclic diol (B-1), and the composition forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more. (2) The urethane resin-forming composition according to (1), which forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more and 4700 mmol / kg or less. (3) The urethane resin-forming composition according to (1) or (2), which forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more and 3800 mmol / kg or less. (4) The urethane resin-forming composition according to any one of (1) to (3), wherein at least one of the component (a) and the curing agent (B) comprises a polyfunctional component having three or more reactive groups. (5) The urethane resin-forming composition according to (4), wherein the content of structural units derived from the polyfunctional component forms a urethane resin of 50 mmol / kg or more and 1,000 mmol / kg or less. (6) The urethane resin-forming composition according to any one of (1) to (5), wherein the polyol (a-1) has a number average molecular weight of 2,500 or more. (7) The urethane resin-forming composition according to any one of (1) to (6), wherein the solvent content is 1.0 mass% or less. (8) The urethane resin-forming composition according to any one of (1) to (7), further comprising a filler (C). (9) The urethane resin-forming composition according to any one of (1) to (8), wherein at least one of the base agent (A) and the curing agent (B) is liquid at 25°C and 1 atmosphere. (10) A two-component adhesive comprising the urethane resin-forming composition according to any one of (1) to (9). (11) An adhesive for automobile structure comprising the urethane resin-forming composition according to any one of (1) to (9). (12) A cured product of the urethane resin-forming composition according to any one of (1) to (9).(13) A method for producing a cured product, comprising: mixing a first agent containing a main agent (A) with a second agent containing a curing agent (B) to obtain a cured product containing a urethane resin, wherein the main agent (A) contains an isocyanate-terminated prepolymer (A-1) that is a reaction product of a component (a) containing one or more polyols (a-1) selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2) and a polyisocyanate (a-2), the curing agent (B) contains an alicyclic diol (B-1), and the urethane resin has a urethane group concentration of 2800 mmol / kg or more. (14) A method for producing a cured product according to (13), wherein the urethane resin has a urethane group concentration of 2800 mmol / kg or more and 4700 mmol / kg or less. (15) The method for producing a cured product according to (13) or (14), wherein the urethane resin has a urethane group concentration of 2800 mmol / kg or more and 3800 mmol / kg or less. (16) The method for producing a cured product according to any one of (13) to (15), wherein at least one of the component (a) and the curing agent (B) contains a polyfunctional component. (17) The method for producing a cured product according to (16), wherein the urethane resin contains structural units derived from the polyfunctional component in an amount of 50 mmol / kg or more and 1000 mmol / kg or less. (18) The method for producing a cured product according to any one of (13) to (17), wherein the polyol (a-1) has a number average molecular weight of 2500 or more. (19) The method for producing a cured product according to any one of (13) to (18), wherein the content of the solvent in the first part and the second part is 1.0 mass% or less, based on the total amount of the first part and the second part. (20) The method for producing a cured product according to any one of (13) to (19), wherein at least one of the first agent and the second agent further contains a filler (C). (21) The method for producing a cured product according to any one of (13) to (20), wherein at least one of the main agent (A) and the curing agent (B) is liquid at 25°C and 1 atmosphere.

[0010] According to one aspect of the present disclosure, it is possible to provide a urethane resin-forming composition and an adhesive capable of forming a cured product in which change in elastic modulus is suppressed over a wide temperature range. Also, according to another aspect of the present disclosure, it is possible to provide a cured product in which change in elastic modulus is suppressed over a wide temperature range and a method for producing the same.

[0011] Exemplary embodiments for implementing each aspect of the present disclosure will now be described in detail.

[0012] [Urethane Resin-Forming Composition] A urethane resin-forming composition according to one embodiment of the present disclosure comprises a base component (A) and a curing agent (B). The urethane resin-forming composition may be a two-component type in which the base component (A) and the curing agent (B) are present separately, a one-component type in which the base component (A) and the curing agent (B) are combined, or a three-component or more multi-component type. If a one-component composition is required for long-term storage, it is preferable to take known measures to prevent functional groups from reacting in the one-component state, such as blocking the isocyanate group-terminated prepolymer (A-1). When the urethane resin-forming composition is a two-component or multi-component composition, the urethane resin-forming composition may comprise, for example, a first component containing the base component (A) and a second component containing the curing agent (B). In any of the one-component, two-component, and multi-component compositions, each component may be in a liquid state when used, and may be solid at room temperature, for example.

[0013] The main component (A) contains an isocyanate-terminated prepolymer (A-1) which is a reaction product of a component (a) containing one or more polyols (a-1) selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2) and a polyisocyanate (a-2).

[0014] The curing agent (B) includes an alicyclic diol (B-1).

[0015] The urethane resin-forming composition is a composition that forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more (preferably 2800 mmol / kg or more and 4700 mmol / kg or less, more preferably 2800 mmol / kg or more and 3800 mmol / kg or less). In other words, the urethane resin-forming composition is a composition in which the main component (A) and the curing agent (B) are selected so as to form a urethane resin having a urethane group concentration of 2800 mmol / kg or more (preferably 2800 mmol / kg or more and 4700 mmol / kg or less, more preferably 2800 mmol / kg or more and 3800 mmol / kg or less).

[0016] With such a urethane group concentration, the fracture toughness value (G １ｃ ) tends to be higher, resulting in a cured product with better toughness. Fracture toughness is considered a composite index of flexibility and rigidity and is expressed as a unit of energy. A higher fracture toughness value means that the adhesive has better resistance when energy is applied (such as to impact), so the higher the value, the better.

[0017] By curing the urethane resin-forming composition, it is possible to obtain a cured product in which the change in elastic modulus is suppressed over a wide temperature range (for example, from −30° C. to 80° C.).

[0018] [Main component (A)] The main component (A) contains an isocyanate-terminated prepolymer (A-1), which is a reaction product of a component (a) containing a polyol (a-1) and a polyisocyanate (a-2).

[0019] The polyol (a-1) is at least one selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2).

[0020] Examples of the polyether polyol (a-1-1) include polyether polyols which are addition polymers of alkylene oxides using a compound having two active hydrogen groups as an initiator, and polyether polyols which are ring-opening polymers of cyclic ethers. The compound having two active hydrogen groups may be one or more types, and examples thereof include polyols (e.g., ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, diol dimer acid, bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, etc.), polyamines (e.g., ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, xylylenediamine, etc.), and the like. The alkylene oxides may be one or more types, such as ethylene oxide, propylene oxide, butylene oxide, etc. The cyclic ethers may be one or more types, such as alkyl glycidyl ethers (e.g., methyl glycidyl ether, etc.), aryl glycidyl ethers (e.g., phenyl glycidyl ether, etc.), tetrahydrofuran, etc.

[0021] Examples of the polycarbonate polyol (a-1-2) include condensation polymers of polyols, carbonates, and the like. The polyols may be one or more kinds, and examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, glycerin, trimethylolpropane, diol dimer acid, an ethylene oxide adduct of bisphenol A, a propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, and xylylene glycol. The carbonates may be one or more types, and may be, for example, dialkyl carbonates (e.g., dimethyl carbonate, diethyl carbonate, etc.), alkylene carbonates (e.g., ethylene carbonate, propylene carbonate, etc.), diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, diphenanthryl carbonate, diindanyl carbonate, etc.

[0022] When the polyol (a-1) is a polyether polyol (a-1-1), the urethane resin-forming composition tends to have a cured product in which change in elastic modulus is more significantly suppressed.

[0023] The number average molecular weight of the polyol (a-1) is preferably 2,500 or more, more preferably 2,500 or more and 10,000 or less, and even more preferably 2,500 or more and 7,000 or less. In the present disclosure, the number average molecular weight of the polyol (a-1) is a value measured by a method (titration method) in accordance with JIS K 0070-1992.

[0024] The content of polyol (a-1) may be, for example, 5% by mass or more, 10% by mass or more, 12% by mass or more, or 15% by mass or more, based on the total amount of component (a). When the content of polyol (a-1) is high, the fracture toughness value tends to be further improved. Furthermore, the content of polyol (a-1) may be, for example, 61% by mass or less, 59% by mass or less, 57% by mass or less, or 55% by mass or less, based on the total amount of component (a). When the content of polyol (a-1) is low, the change in elastic modulus of the cured product tends to be further suppressed.

[0025] In the urethane resin formed from the urethane resin-forming composition, the content of the structural unit derived from polyol (a-1) may be, for example, 10 mmol / kg or more, 20 mmol / kg or more, 30 mmol / kg or more, 40 mmol / kg or more, 50 mmol / kg or more, etc., and 200 mmol / kg or less, 180 mmol / kg or less, 160 mmol / kg or less, 140 mmol / kg or less, 130 mmol / kg or less, 120 mmol / kg or less, 110 mmol / kg or less, 100 mmol / kg or less, etc. Furthermore, in the urethane resin formed from the urethane resin-forming composition, the content of the structural unit derived from polyol (a-1) is preferably 10 mmol / kg or more and 130 mmol / kg or less, more preferably 30 mmol / kg or more and 100 mmol / kg or less. In other words, the urethane resin-forming composition may be a composition in which the main component (A) and the curing agent (B) are selected so that a urethane resin having a content of the structural unit derived from polyol (a-1) in the above range is formed. In the urethane resin-forming composition, the polyol (a-1) may also be blended with the curing agent (B). That is, the "content of structural units derived from polyol (a-1)" may be the total amount of structural units derived from polyol (a-1) in component (a) and structural units derived from polyol (a-1) in the curing agent (B).

[0026] The polyisocyanate (a-2) may be a polyisocyanate having two or more isocyanate groups in the molecule, and is preferably a polyisocyanate (diisocyanate) having two isocyanate groups in the molecule.

[0027] Examples of polyisocyanates include aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. These may be used alone or in combination of two or more. Among these, aromatic polyisocyanates are preferred from the viewpoints of reactivity, viscosity, and the like.

[0028] Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a 2,4-tolylene diisocyanate / 2,6-tolylene diisocyanate mixture, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, a 2,2'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate mixture, 2,4'-diphenylmethane diisocyanate, a 2,4'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate mixture, and a 2,2'-diphenylmethane diisocyanate / 2,4'-diphenylmethane diisocyanate / Examples of the diisocyanate include 4,4'-diphenylmethane diisocyanate mixture, m-xylylene diisocyanate, p-xylylene diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate.

[0029] Examples of the aromatic aliphatic polyisocyanate include 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, a 1,3-xylylene diisocyanate / 1,4-xylylene diisocyanate mixture, 1,3-bis(1-isocyanato-1-methylethyl)benzene, 1,4-bis(1-isocyanato-1-methylethyl)benzene, a 1,3-bis(1-isocyanato-1-methylethyl)benzene / 1,4-bis(1-isocyanato-1-methylethyl)benzene mixture, and ω,ω'-diisocyanato-1,4-diethylbenzene.

[0030] Examples of aliphatic polyisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, ethylene diisocyanate, trimethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, 2,2'-dimethylpentane diisocyanate, 2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate, and 2,4,4-trimethylhexane diisocyanate. Examples of the isocyanate include ethylene diisocyanate, 1,6,11-undecane triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanate-4-isocyanate methyl octane, 2,5,7-trimethyl-1,8-diisocyanate-5-isocyanate methyl octane, bis(isocyanate ethyl) carbonate, bis(isocyanate ethyl) ether, 1,4-butylene glycol dipropyl ether-α,α'-diisocyanate, lysine diisocyanate methyl ester, 2-isocyanate ethyl-2,6-diisocyanate hexanoate, and 2-isocyanate propyl-2,6-diisocyanate hexanoate.

[0031] Examples of alicyclic polyisocyanates include isophorone diisocyanate, cyclohexane diisocyanate, bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, dicyclohexyldimethylmethane diisocyanate, 2,2'-dimethyldicyclohexylmethane diisocyanate, bis(4-isocyanato-n-butylidene)pentaerythritol, hydrogenated dimer acid diisocyanate, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane 2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane Examples of isocyanate diisocyanates include 2-isocyanatemethyl-2-(3-isocyanatepropyl)-6-(2-isocyanateethyl)-bicyclo-[2.2.1]-heptane, 2,5-bis(isocyanatemethyl)-bicyclo[2.2.1]-heptane, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated hydrogenated tetramethylxylene diisocyanate.

[0032] The content of polyisocyanate (a-2) may be, for example, 40% by mass or more, 42% by mass or more, 44% by mass or more, or 46% by mass or more, based on the total amount of component (a). When the content of polyisocyanate (a-2) is high, the change in elastic modulus of the cured product tends to be further suppressed. Furthermore, the content of polyisocyanate (a-2) may be, for example, 95% by mass or less, 90% by mass or less, 88% by mass or less, or 85% by mass or less, based on the total amount of component (a). When the content of polyisocyanate (a-2) is low, the fracture toughness value tends to be further improved.

[0033] In the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from polyisocyanate (a-2) is preferably 1000 mmol / kg or more and 3000 mmol / kg or less, and more preferably 1500 mmol / kg or more and 2500 mmol / kg or less. In other words, the urethane resin-forming composition may be a composition in which the base agent (A) and the curing agent (B) are selected so that a urethane resin having a content of structural units derived from polyisocyanate (a-2) in the above-mentioned range is formed. It can also be said that the content of structural units derived from polyisocyanate (a-2) in the isocyanate group-terminated prepolymer (A-1) in the urethane resin-forming composition may be in the above-mentioned range.

[0034] Component (a) may contain a polyfunctional component. The polyfunctional component is a compound having three or more reactive groups. The reactive group may be any group that can react with an isocyanate group or a hydroxy group to form a bond. The reactive group may be, for example, an isocyanate group or an active hydrogen group (e.g., a hydroxy group, an amino group, etc.). The polyfunctional component may be used alone or in combination of two or more types.

[0035] The polyfunctional component may be a polyol (a-1), a polyisocyanate (a-2), or a compound (a-3) other than the polyol (a-1) and the polyisocyanate (a-2).

[0036] The compound (a-3) may be a compound having three or more active hydrogen groups, a compound having three or more hydroxy groups, or a compound having three hydroxy groups. Examples of the compound (a-3) include glycerin, trimethylolpropane, pentaerythritol, N,N-bishydroxypropyl-N-hydroxyethylamine, triethanolamine, triisopropanolamine, a monomer polyol of an ethylenediamine propylene oxide modified product, a monomer polyol of a trimethylolpropane propylene oxide modified product, and a pentaerythritol propylene oxide modified product. Examples of the compound (a-3) include polycaprolactone polyols, which are ring-opening addition polymers of polyols having three or more hydroxy groups (e.g., glycerin, trimethylolpropane, pentaerythritol, etc.) and cyclic esters (e.g., ε-caprolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, etc.).

[0037] The content of the polyfunctional component may be, for example, 10% by mass or less, 7% by mass or less, 5% by mass or less, or 3% by mass or less, based on the total amount of component (a). Component (a) may not contain a polyfunctional component, and the content of the polyfunctional component may be 0% by mass or more, based on the total amount of component (a).

[0038] In the urethane resin formed from the urethane resin-forming composition, the content of the structural unit derived from the polyfunctional component is preferably 1500 mmol / kg or less, more preferably 25 mmol / kg or more and 1250 mmol / kg or less, and particularly preferably 50 mmol / kg or more and 1000 mmol / kg or less. When the content of the structural unit derived from the polyfunctional component is within the above range, the fracture toughness value (G １ｃ) and tends to produce a cured product with excellent toughness. In other words, the urethane resin-forming composition may be a composition in which the base component (A) and the curing agent (B) are selected so that a urethane resin having a content of structural units derived from the polyfunctional component within the above range is formed. In the urethane resin-forming composition, the polyfunctional component may also be blended into the curing agent (B). In other words, the "content of structural units derived from the polyfunctional component" may be the total amount of structural units derived from the polyfunctional component in component (a) and structural units derived from the polyfunctional component in the curing agent (B).

[0039] In the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from crosslinkable groups contained in the polyfunctional component is preferably 1500 mmol / kg or less, more preferably 25 mmol / kg or more and 1250 mmol / kg or less, and particularly preferably 50 mmol / kg or more and 1000 mmol / kg or less. When the content of structural units derived from crosslinkable groups is within the above range, the fracture toughness value (G １ｃ ) and tends to produce a cured product with excellent toughness. In other words, the urethane resin-forming composition may be a composition in which the main component (A) and the curing agent (B) are selected so that a urethane resin having a content of structural units derived from crosslinkable groups in the above range is formed. In the urethane resin-forming composition, a polyfunctional component may also be blended in the curing agent (B). In other words, the "content of structural units derived from crosslinkable groups" may be the total amount of structural units derived from crosslinkable groups possessed by the polyfunctional component in component (a) and structural units derived from crosslinkable groups possessed by the polyfunctional component in curing agent (B).

[0040] Here, the crosslinkable group is a functional group that forms a crosslink. Taking a trifunctional polyol (for example, glycerin) as an example, one hydroxy group in one molecule forms a crosslink, and the remaining two hydroxy groups do not contribute to the crosslinking, so in this case there is one crosslinkable group. That is, in the case of a trifunctional polyol, the content of the crosslinkable group is synonymous with the content of the trifunctional polyol, since the trifunctional polyol has one crosslinkable group.

[0041] The component (a) may further contain, as a component other than the polyol (a-1) and the polyisocyanate (a-2), one or more diols (a-4) selected from the group consisting of the alicyclic diol (B-1) described below and the diol (B-3) having a number average molecular weight of less than 1,000.

[0042] The content of diol (a-4) may be, for example, 5% by mass or less, 4% by mass or less, 3% by mass or less, or 2% by mass or less, based on the total amount of component (a). Component (a) may not contain diol (a-4), and the content of diol (a-4) may be 0% by mass or more, based on the total amount of component (a).

[0043] In component (a), at least one of the polyol (a-1) and the polyisocyanate (a-2) is preferably liquid at 25° C. and 1 atmosphere.

[0044] In component (a), the ratio of the total number of hydroxy groups to the total number of isocyanate groups (OH / NCO) may be, for example, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and the ratio (OH / NCO) in component (a) may be, for example, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less.

[0045] The isocyanate group-terminated prepolymer (A-1) is a reaction product of the component (a). The isocyanate group-terminated prepolymer (A-1) may be a reaction product in which all of the component (a) has reacted, or may be a reaction product in which only a portion of the component (a) has reacted.

[0046] The reaction conditions for component (a) are not particularly limited as long as they allow the isocyanate groups and hydroxy groups in component (a) to react to form urethane bonds. The reaction temperature for component (a) may be, for example, 70 to 80°C. The reaction time for component (a) may be, for example, 2 to 6 hours.

[0047] The isocyanate group-terminated prepolymer (A-1) is preferably liquid at 25° C. and 1 atmosphere.

[0048] The main component (A) may contain other components in addition to the isocyanate group-terminated prepolymer (A-1). The other components are preferably those that do not react with the functional groups of the isocyanate group-terminated prepolymer (A-1) and the curing agent (B) described below (for example, a colorant, an antistatic agent, an antiseptic, etc.).

[0049] The main component (A) is preferably liquid at 25° C. and 1 atmosphere.

[0050] [Curing Agent (B)] The curing agent (B) contains an alicyclic diol (B-1). The alicyclic diol (B-1) may be used alone or in combination of two or more.

[0051] Examples of the alicyclic diol (B-1) include 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, 1,4-cyclohexanedimethanol, hydroxypropylcyclohexanol, isohexide, tricyclo[5.2.1.0] ２，６ ]decane-4,8-dimethanol, and alkylene oxide adducts thereof.

[0052] The number average molecular weight of the alicyclic diol (B-1) is preferably 500 g / mol or less, and more preferably 250 g / mol or less. In the present disclosure, the number average molecular weight is a value measured by a method (titration method) in accordance with JIS K 0070-1992.

[0053] In the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from the alicyclic diol (B-1) is preferably 100 mmol / kg or more and 3000 mmol / kg or more, and more preferably 400 mmol / kg or more and 2000 mmol / kg or less. In other words, the urethane resin-forming composition may be a composition in which the base component (A) and the curing agent (B) are selected so as to form a urethane resin having a content of structural units derived from the alicyclic diol (B-1) within the above range. In the urethane resin-forming composition, the alicyclic diol (B-1) may also be blended with the above-mentioned component (a). In other words, the "content of structural units derived from the alicyclic diol (B-1)" may be the total amount of structural units derived from the alicyclic diol (B-1) in component (a) and structural units derived from the alicyclic diol (B-1) in the curing agent (B).

[0054] The curing agent (B) may further contain a multifunctional component. The multifunctional component is a compound having three or more reactive groups. The multifunctional component may be used alone or in combination of two or more. Examples of the multifunctional component include the same multifunctional components as those in component (a).

[0055] The polyfunctional component contained in the curing agent (B) is preferably a compound (B-2) having three or more hydroxy groups.

[0056] Examples of the compound (B-2) include glycerin, trimethylolpropane, pentaerythritol, N,N-bishydroxypropyl-N-hydroxyethylamine, triethanolamine, triisopropanolamine, a monomer polyol of an ethylenediamine propylene oxide modified product, a monomer polyol of a trimethylolpropane propylene oxide modified product, and a pentaerythritol propylene oxide modified product. Examples of the compound (B-2) also include polycaprolactone polyols, which are ring-opening addition polymers of polyols having three or more hydroxy groups (e.g., glycerin, trimethylolpropane, pentaerythritol, etc.) and cyclic esters (e.g., ε-caprolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, etc.).

[0057] The content of the polyfunctional component may be, for example, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, etc., based on the total amount of the curing agent (B). The curing agent (B) may not contain a polyfunctional component, and the content of the polyfunctional component may be 0% by mass or more based on the total amount of the curing agent (B).

[0058] The content of the structural units derived from the polyfunctional component in the urethane resin formed from the urethane resin-forming composition is as described above.

[0059] The curing agent (B) may further contain the compounds exemplified above as the polyol (a-1).

[0060] The curing agent (B) may further contain, as a component other than the alicyclic diol (B-1) and polyol (a-1), a diol (B-3) having a number average molecular weight of less than 1000. The diol (B-3) more preferably has a number average molecular weight of less than 500.

[0061] The diol (B-3) may, for example, be an aliphatic diol (B-3-1).

[0062] Examples of the aliphatic diol (B-3-1) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, neopentyl glycol, diethylene glycol, and dipropylene glycol.

[0063] In the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from the aliphatic diol (B-3-1) may be, for example, 1300 mmol / kg or less, 1200 mmol / kg or less, or 1100 mmol / kg or less. Furthermore, in the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from the aliphatic diol (B-3-1) may be, for example, 0 mmol / kg or more, 100 mmol / kg or more, or 200 mmol / kg or more. In other words, the urethane resin-forming composition may be a composition in which the base agent (A) and the curing agent (B) are selected so that a urethane resin having a content of structural units derived from the aliphatic diol (B-3-1) within the above range is formed. In addition, in the urethane resin-forming composition, the aliphatic diol (B-3-1) may also be blended with the above-mentioned component (a). That is, the "content of structural units derived from aliphatic diol (B-3-1)" may be the total amount of structural units derived from aliphatic diol (B-3-1) in component (a) and structural units derived from aliphatic diol (B-3-1) in curing agent (B).

[0064] The diol (B-3) also includes a diol (B-3-2) having at least one bond selected from the group consisting of an ether bond, an ester bond, and a carbonate bond, such as a polyether polyol, a polycarbonate polyol, or a polyester polyol.

[0065] Examples of the polyether polyol and polycarbonate polyol are the same as those mentioned above.

[0066] Examples of polyester polyols include condensation polymers of polyols and dicarboxylic acids or anhydrides thereof. The polyols may be one or more, and examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, glycerin, trimethylolpropane, diol dimer acid, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, and xylylene glycol. Examples of dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α,β-diethylsuccinic acid, maleic acid, and fumaric acid.

[0067] Examples of the diol (B-3-2) include polyester-amide polyols obtained by replacing part of the polyols in the polyester polyols described above with low-molecular-weight polyamines or low-molecular-weight amino alcohols such as hexamethylenediamine, isophoronediamine, and monoethanolamine.

[0068] In the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from diol (B-3-2) may be, for example, 100 mmol / kg or less, 80 mmol / kg or less, or 60 mmol / kg or less. Furthermore, in the urethane resin formed from the urethane resin-forming composition, the content of structural units derived from diol (B-3-2) may be, for example, 0 mmol / kg or more, 5 mmol / kg or more, or 10 mmol / kg or more. In other words, the urethane resin-forming composition may be a composition in which the base agent (A) and curing agent (B) are selected so that a urethane resin having a content of structural units derived from diol (B-3-2) within the above range is formed. In addition, in the urethane resin-forming composition, diol (B-3-2) may also be blended with the above-mentioned component (a). That is, the "content of structural units derived from diol (B-3-2)" may be the total amount of structural units derived from diol (B-3-2) in component (a) and structural units derived from diol (B-3-2) in curing agent (B).

[0069] The curing agent (B) may further contain an active hydrogen-containing compound as a component other than those described above. Examples of such active hydrogen-containing compounds include compounds having functional groups such as amino groups, thiol groups, and carboxyl groups. These active hydrogen-containing compounds can be used alone or in combination of two or more.

[0070] The curing agent (B) may contain other components in addition to those described above. The other components are preferably those that do not react with the functional groups of the isocyanate group-terminated prepolymer (A-1) and the curing agent (B) (for example, a colorant, an antistatic agent, an antiseptic, etc.).

[0071] In the curing agent (B), at least one of the alicyclic diol (B-1) and the diol (B-3) is preferably liquid at 25°C and 1 atmospheric pressure, and more preferably both are liquid at 25°C and 1 atmospheric pressure.

[0072] The ratio (B / A) of the total number of hydroxy groups in the curing agent (B) to the total number of isocyanate groups in the base component (A) may be, for example, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. Furthermore, the ratio (B / A) may be, for example, 1.2 or less, 1.15 or less, 1.10 or less, or 1.05 or less. When the ratio (B / A) is within the above range, the resin strength tends to be further improved. When the urethane resin-forming composition is a two-component type, the urethane resin-forming composition may be a two-component composition in which the base component (A) and the curing agent (B) are mixed so that the ratio (B / A) satisfies the above ratio.

[0073] The curing agent (B) is preferably liquid at 25° C. and 1 atmosphere.

[0074] In the urethane resin-forming composition, from the viewpoint of handling properties, it is preferable that at least one of the base agent (A) and the curing agent (B) is liquid at 25°C and 1 atmosphere, and it is more preferable that both are liquid at 25°C and 1 atmosphere.

[0075] [[Filler (C)]] The urethane resin-forming composition may further contain a filler (C). When the urethane resin-forming composition is a two-component type, the filler (C) may be contained in the first part together with the main component (A), in the second part together with the curing agent (B), or in both the first and second parts. That is, the urethane resin-forming composition may, for example, contain a first part containing the main component (A) and the filler (C) and a second part containing the curing agent (B), a first part containing the main component (A) and the filler (C) and a second part containing the curing agent (B) and the filler (C), or a first part containing the main component (A) and the filler (C) and a second part containing the curing agent (B) and the filler (C).

[0076] Examples of the filler (C) include known fillers. The filler (C) may be, for example, an inorganic filler or an organic filler, and is preferably an inorganic filler. The filler (C) may be used alone or in combination of two or more.

[0077] Examples of inorganic fillers include talc, zeolite, silica, microballoons, clay, glass balloons, carbon black, calcium carbonate, etc. The inorganic fillers are not limited to these. These can be used alone or in combination of two or more.

[0078] Examples of organic fillers include polyamide particles, acrylic particles, carbon nanotubes, starch, natural organic fibers, and synthetic fibers.

[0079] The content of the filler (C) is, for example, preferably 10% by mass or more and 70% by mass or less, and more preferably 10% by mass or more and 50% by mass or less, relative to the total mass of the urethane resin-forming composition. When the content of the filler (C) is 10% by mass or more, dripping can be more effectively suppressed. When the content of the filler (C) is 70% by mass or less, the filler (C) and other components are more easily mixed uniformly, resulting in better adhesive strength and coatability. When the urethane resin-forming composition is a two-component type, the total mass of the urethane resin-forming composition may be the combined amount of the first and second components mixed to form a cured product.

[0080] The urethane resin-forming composition may be a two-component type in which a first component containing the main component (A) and a second component containing the curing agent (B) are present separately, or may be a one-component type in which the main component (A) and the curing agent (B) are mixed together.

[0081] The temperature and time for mixing the first and second agents may be, for example, 10 to 35° C. and 1 to 60 minutes.

[0082] The method for mixing the first and second agents is not particularly limited, and for example, they may be mixed manually with a spatula, or may be mixed using a mechanical rotary mixer, static mixer, or the like.

[0083] The urethane resin-forming composition preferably has a solvent content of 1.0 mass % or less. The urethane resin-forming composition may also be substantially solvent-free, i.e., solvent-free. However, if a solvent is contained as an impurity, the composition falls into the category of being substantially solvent-free.

[0084] When the urethane resin-forming composition is a two-component type, the content of the solvent in the first part is preferably 1.0 mass% or less, and the content of the solvent in the second part is preferably 1.0 mass% or less. Furthermore, the content of the solvent in the first part and the second part to be mixed is preferably 1.0 mass% or less relative to the total amount of the first part and the second part to be mixed to form a cured product.

[0085] The urethane resin-forming composition can be suitably used as an adhesive (particularly a two-component adhesive) for various applications, such as in the automotive, display, recording medium, electronic materials, batteries, optical components, architecture, electronic devices, and aviation fields.

[0086] In the automotive field, the material can be used for, for example, automobile structural parts, switches, headlamps, internal engine parts, electrical parts, drive engines, and brake oil tanks. In the display field, the material can be used for, for example, liquid crystal displays, organic electroluminescence, and light-emitting diode display devices. In the recording medium field, the material can be used for, for example, video discs, CDs, DVDs, MDs, pickup lenses, VCM magnets, spindle motors, hard disk peripheral parts, and Blu-ray discs.

[0087] In the field of electronic materials, the material can be used, for example, in electronic components, electrical circuits, electrical contacts, or semiconductor elements. More specific examples of these applications include sealing materials, die bonding agents, conductive adhesives, anisotropic conductive adhesives, and interlayer adhesives for multilayer substrates, including build-up substrates. In the field of batteries, the material can be used, for example, in lithium-ion batteries, manganese batteries, alkaline batteries, nickel-based batteries, fuel cells, silicon-based solar cells, dye-sensitized solar cells, and organic solar cells. In the field of optical components, the material can be used, for example, in optical fiber materials, optical passive components, optical circuit components, and optoelectronic integrated circuits, in the periphery of optical switches and optical connectors in optical communication systems. In the field of electronic devices, the material can be used, for example, in camera modules.

[0088] The urethane resin-forming composition has good stability of physical properties in the temperature range in which it is used (for example, from −30° C. to 80° C.), and therefore can be particularly suitably used as an adhesive for automobile structures.

[0089] [Cured Product] A cured product according to one embodiment of the present disclosure is a cured product of the urethane resin-forming composition described above.

[0090] The cured product contains a urethane resin, which is a reaction product of the base resin (A) and the curing agent (B).

[0091] The urethane group concentration of the urethane resin in the cured product may be 2800 mmol / kg or more, preferably 2800 mmol / kg or more and 4700 mmol / kg or less, and more preferably 2800 mmol / kg or more and 3800 mmol / kg or less. With such a urethane group concentration, the fracture toughness value (G １ｃ ) tends to be higher, resulting in a cured product with better toughness.

[0092] The urethane resin-forming composition is cured by reacting the main component (A) with the curing agent (B). The urethane resin-forming composition may be cured, for example, by mixing the first component and the second component and reacting the main component (A) with the curing agent (B).

[0093] The reaction conditions for reacting the main component (A) with the curing agent (B) are not particularly limited, and for example, the heating temperature may be 100 to 200° C. and the heating time may be 20 minutes to 10 hours. The reaction between the main component (A) and the curing agent (B) may be carried out in a single heating step or in two or more heating steps.

[0094] In the present disclosure, the fracture toughness value of a cured product is measured by the DCP test using the following method. The DCP test was performed in accordance with ASTM D3433-99. Resin thickness: adjusted to 0.35 mm using a spacer. Teflon (registered trademark) tape was used as the spacer. Test specimen shape: Contoured type was used. Test substrate: S50C steel (electroless nickel plated). Test conditions: tensioned at 2 mm / min, and the fracture toughness value G was calculated based on the maximum load. １ｃ Calculation formula: G １ｃ = [4L２ (max)](m) / [EB ２ ] L (max) Load: (N) E Young's modulus of substrate (MPa): 208000 B Width of substrate (mm): 25.49 m Constant (from contoured mold): 3.54

[0095] In the present disclosure, the modulus of elasticity of a cured product is measured by the following viscoelasticity measurement. A measurement sample is obtained by cutting the cured product using a dumbbell for viscoelasticity measurement, and the modulus of elasticity is measured by performing viscoelasticity measurement under the following measurement conditions: Frequency: 10 Hz; Heating rate: 2°C / min; Measurement temperature: -100°C to 250°C; Measurement device: Viscoelasticity measuring device DMA7100 manufactured by Hitachi High-Tech Science Corporation.

[0096] The present invention will be explained in more detail below based on examples, but the present invention is not limited to the following examples.

[0097] [Raw Materials] Examples and comparative examples were carried out using the following raw materials. "MT": Millionate MT (monomeric MDI, manufactured by Tosoh Corporation) Molecular weight: 250, f = 2 "N-968": Amorphous polycarbonate polyol N-968 (manufactured by Tosoh Corporation) Hydroxyl value = 37.5 KOH mg / g, f = 2 "TMP": Trimethylolpropane (manufactured by Mitsubishi Gas Chemical Company, Inc.) Molecular weight: 134, f = 3 "PTG-L3500": Amorphous polytetramethylene ether glycol (manufactured by Hodogaya Chemical Co., Ltd.) Number average molecular weight: 3500, f = 2 "PCD3000": Polycarbonate polyol N-969 (manufactured by Tosoh Corporation) Number average molecular weight: 3000, f = 2 "PES3000": Polyester polyol Kuraray Polyol P-3010 (manufactured by Kuraray Co., Ltd.) Number average molecular weight: 3000, f = 2 "BG": Butylene glycol (manufactured by Mitsubishi Chemical Corporation) 1,4-butanediol, molecular weight 90, f=2 "CHDM": 1,4-cyclohexanedimethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) "Zeolite": Zeolum A-3 (manufactured by Tosoh Corporation) "Talc": Crown Talc R (manufactured by Matsumura Sangyo Co., Ltd.) "TDDM": Tricyclo 5.2.1.0 ２，６ Decane-4,8-dimethanol (Sigma-Aldrich)

[0098] (Examples 1 to 24, Comparative Examples 1 to 6) Each raw material for the main component was charged into a 2 L stirring vessel filled with nitrogen and stirred according to the formulations shown in Tables 1 to 6. Thereafter, the temperature inside the stirring vessel was maintained at 70 to 80°C, and the urethane reaction was allowed to proceed for about 2 to 5 hours, thereby obtaining main component (A).

[0099] Next, filler (C) (talc 50% by mass / zeolite 50% by mass) was added to the main component (A) so that the amount of filler in the system was 1 / 3 (mass ratio), and the mixture was mixed and degassed to obtain a first component.

[0100] Furthermore, the raw materials for the curing agent were charged into a 2 L stirring vessel filled with nitrogen and stirred according to the formulations shown in Tables 1 to 6. Thereafter, the mixture was mixed and stirred for about 1 to 3 hours while maintaining the temperature inside the stirring vessel at 70 to 80°C, thereby obtaining curing agent (B). This curing agent (B) was used as the second agent.

[0101] [DCB Test (Fracture Toughness)] The DCB test was conducted in accordance with ASTM D3433-99 under the following conditions: Resin thickness: adjusted to 0.35 mm using a spacer (Teflon (registered trademark) tape was used as the spacer); Test piece shape: Contoured type was used; Test substrate: S50C steel (electroless nickel plated); Test conditions: tensioned at 2 mm / min, and the fracture toughness value G was calculated based on the maximum load. １ｃ Calculation formula: G １ｃ = [4L ２ (max)](m) / [EB ２ ] L (max) Load: (N) E Young's modulus of substrate (MPa): 208000 B Width of substrate (mm): 25.49 m Constant (from contoured mold): 3.54

[0102] Specifically, the first and second agents were mixed according to the compositions shown in Tables 1 to 6, stirred for 30 seconds, and then applied to a first substrate. To create a preliminary crack in the test specimen, a 0.35 mm thick Teflon (registered trademark) seal was attached to the first substrate over a 4.9 cm area from one end. To ensure a uniform adhesive coating thickness, a 0.35 mm thick Teflon (registered trademark) seal was attached to the first substrate over a 2 cm area from the other end. A second substrate was placed on the coated surface and fixed with a clamp. Next, a two-stage heat treatment was performed at 130°C for 1.5 hours and 110°C for 20 hours to cure the adhesive, yielding a test specimen. The obtained test specimen was subjected to a DCB test under the above conditions, and the fracture toughness value G １ｃ The results are shown in Tables 1 to 6.

[0103] [Cohesive Failure Rate] After the DCB test, the fractured surface of the sample was visually observed, and the area ratio of the fractured cured layer was measured. The measurement results are shown in Tables 1 to 6. Cohesive failure: A state in which the cured layer was fractured. Interfacial failure: A state in which the cured material appears to have peeled off at the interface with the substrate.

[0104] [DMA Measurement (Measurement of Elastic Modulus)] The elastic modulus was measured under the following conditions: Frequency: 10 Hz; Heating rate: 2°C / min; Measurement temperature: -100°C to 250°C; Measurement device: Viscoelasticity measuring device DMA7100 manufactured by Hitachi High-Tech Science Corporation.

[0105] Specifically, the first and second parts were mixed in a 1:1 (mass ratio), stirred for 30 seconds, and then poured into a mold with a 2 mm-thick spacer. The mixture was cured by two-stage heat treatment at 130°C for 1.5 hours and 110°C for 20 hours to obtain a cured product. The cured product was then cut out using a viscoelasticity dumbbell to obtain test specimens. DMA measurements were performed on the obtained test specimens under the above conditions. The results of measuring the elastic modulus at -30°C and 80°C are shown in Tables 1 to 6. The elastic modulus retention at 80°C relative to the elastic modulus at -30°C was also determined and reported in Tables 1 to 6 as "elastic modulus retention (%)."

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] In Examples 1 to 15 and Comparative Examples 1 to 3, in which the polyol (a-1) was polyether polyol (a-1-1), the elastic modulus retention rates of Examples 1 to 15 were higher than those of Comparative Examples 1 to 3, and it was confirmed that the change in elastic modulus was suppressed over a wide temperature range. Furthermore, in Examples 1 to 9 and 14 to 15, the fracture toughness values ​​(G １ｃ ) is 0.30 kJ / m ２ Furthermore, it was confirmed that Examples 16 to 24 had excellent cohesive failure rates and high adhesive reliability.

[0113] In Examples 16 to 24 and Comparative Example 4, which are systems in which polyol (a-1) is polycarbonate polyol (a-1-2), the elastic modulus retention rates of Examples 16 to 24 were higher than that of Comparative Example 4, confirming that changes in elastic modulus were suppressed over a wide temperature range. Furthermore, it was confirmed that Examples 16 to 24 were excellent in cohesive failure rate and had high adhesive reliability.

Claims

1. Contains a base agent (A) and a curing agent (B), The base material (A) contains an isocyanate-terminated prepolymer (A-1) which is a reaction product of a component (a) containing one or more polyols (a-1) selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2) and a polyisocyanate (a-2), The polyisocyanate (a-2) includes at least one selected from the group consisting of aromatic polyisocyanates and araliphatic polyisocyanates, The curing agent (B) contains an alicyclic diol (B-1), A urethane resin forming composition that forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more.

2. The urethane resin forming composition according to claim 1 , which forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more and 4700 mmol / kg or less.

3. The urethane resin forming composition according to claim 1 , which forms a urethane resin having a urethane group concentration of 2800 mmol / kg or more and 3800 mmol / kg or less.

4. 2. The urethane resin-forming composition according to claim 1, wherein at least one of the component (a) and the curing agent (B) contains a polyfunctional component having three or more reactive groups.

5. The urethane resin forming composition according to claim 4 , which forms a urethane resin having a content of the structural unit derived from the polyfunctional component of 50 mmol / kg or more and 1000 mmol / kg or less.

6. The urethane resin forming composition according to claim 1, wherein the polyol (a-1) has a number average molecular weight of 2,500 or more.

7. The urethane resin-forming composition according to claim 1 , wherein the solvent content is 1.0 mass % or less.

8. The urethane resin-forming composition according to claim 1 , further comprising a filler (C).

9. 2. The urethane resin-forming composition according to claim 1, wherein at least one of the base agent (A) and the curing agent (B) is liquid at 25°C and 1 atmospheric pressure.

10. A two-component adhesive comprising the urethane resin-forming composition according to any one of claims 1 to 9.

11. An adhesive for automobile structures comprising the urethane resin-forming composition according to any one of claims 1 to 9.

12. A cured product of the urethane resin-forming composition according to any one of claims 1 to 9.

13. The method includes a step of mixing a first agent containing a base agent (A) and a second agent containing a curing agent (B) to obtain a cured product containing a urethane resin, The base material (A) contains an isocyanate-terminated prepolymer (A-1) which is a reaction product of a component (a) containing one or more polyols (a-1) selected from the group consisting of polyether polyols (a-1-1) and polycarbonate polyols (a-1-2) and a polyisocyanate (a-2), The polyisocyanate (a-2) includes at least one selected from the group consisting of aromatic polyisocyanates and araliphatic polyisocyanates, The curing agent (B) contains an alicyclic diol (B-1), The urethane resin has a urethane group concentration of 2800 mmol / kg or more.