Urethane resin-forming composition, cured article and method for producing same, and connected structure and method for producing same

Abstract

A urethane resin-forming composition comprising a main agent (A) and a curing agent (B), wherein: the main agent (A) comprises a polyisocyanate (A-1) and an isocyanate group-terminated prepolymer (A-2), which is a reaction product of the polyisocyanate (A-1) and a polyol (x-1); the curing agent (B) comprises a polyol (B-1), which has a tertiary amino group and three or more hydroxy groups, and a polyol (B-2); the polyol (x-1) and the polyol (B-2) are each independently a polyester polyol or a polycarbonate polyol; and the number average molecular weight of the polyol (B-2) is 2,000 or less.

Description

Urethane resin-forming composition, cured product and method for manufacturing the same, connecting structure and method for manufacturing the same

[0001] This disclosure relates to a urethane resin-forming composition, a cured product and a method for producing the same, a connecting structure and a method for producing the same.

[0002] As a structural adhesive used in industrial products such as automobiles, for example, Patent Document 1 describes a urethane-based adhesive composition.

[0003] 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.

[0004] International Publication No. 2009 / 047962

[0005] When structural adhesives are used in industrial products, if the time required for bonding between components is long, it can lead to decreased manufacturing efficiency or defects due to misalignment.

[0006] This disclosure aims to provide a urethane resin-forming composition that is useful as an adhesive (particularly a structural adhesive) because it has a short time to develop sufficient adhesive strength. Furthermore, this disclosure aims to provide a cured product of the urethane resin-forming composition and a method for producing the same. Finally, this disclosure aims to provide a connecting structure comprising an adhesive layer formed from the urethane resin-forming composition and a method for producing the same.

[0007] This disclosure relates, for example, to the following [1] to

[15] . [1] A urethane resin-forming composition comprising a main component (A) and a curing agent (B), wherein the main component (A) contains a polyisocyanate (A-1) and an isocyanate-terminated prepolymer (A-2) which is a reaction product of the polyisocyanate (A-1) and a polyol (x-1), and the curing agent (B) contains a polyol (B-1) having a tertiary amino group and three or more hydroxyl groups, and a polyol (B-2), wherein the polyol (x-1) and the polyol (B-2) are each independently a polyester polyol or a polycarbonate polyol, and the number average molecular weight of the polyol (B-2) is 2000 or less. [2] The urethane resin-forming composition according to [1], wherein the polyol (x-1) is a polycarbonate polyol. [3] The urethane resin-forming composition according to [1] or [2], wherein the polyol (B-2) is a polycarbonate polyol. [4] The urethane resin-forming composition according to any one of [1] to [3], wherein the number average molecular weight of the polyol (x-1) is 700 or more. [5] The urethane resin-forming composition according to any one of [1] to [4], wherein the number average molecular weight of the polyol (x-1) is greater than the number average molecular weight of the polyol (B-2). [6] The urethane resin-forming composition according to any one of [1] to [5], wherein the content of the polyol (B-1) in the curing agent (B) is 10% by mass or more on a total basis of the curing agent (B). [7] The urethane resin-forming composition according to any one of [1] to [6], wherein at least one of the main component (A) and the curing agent (B) is liquid at 25°C and 1 atm. [8] The urethane resin-forming composition according to any one of [1] to [7], further containing a filler (C). [9] A urethane resin-forming composition according to any one of [1] to [8], which is a two-component adhesive comprising a first agent containing the main agent (A) and a second agent containing the curing agent (B).

[10] A structural adhesive, which is a urethane resin-forming composition according to any one of [1] to [9].

[11] A cured product of a urethane resin-forming composition according to any one of [1] to

[10] .

[12] A method for producing a cured product, comprising the steps of: preparing a urethane resin-forming composition according to any one of [1] to

[10] ; and curing a mixture of the main agent (A) and the curing agent (B) to obtain a cured product containing urethane resin.

[13] A connecting structure comprising: a first member; a second member; and an adhesive layer for bonding the first member and the second member, wherein the adhesive layer contains a cured product of the urethane resin-forming composition according to any one of [1] to

[10] .

[14] The connecting structure according to

[13] , wherein the adhesive surface of the first member and the adhesive surface of the second member are formed of different materials.

[15] A method for manufacturing a connecting structure comprising a first member, a second member, and an adhesive layer for bonding the first member and the second member, comprising the steps of: preparing a urethane resin-forming composition according to any one of [1] to

[10] ; placing a mixture of the main agent (A) and the curing agent (B) between the first member and the second member; and curing the mixture to form the adhesive layer.

[0008] This disclosure provides a urethane resin-forming composition that is useful as an adhesive (particularly a structural adhesive) because it has a short time to develop sufficient adhesive strength. This disclosure also provides a cured product of the urethane resin-forming composition and a method for producing the same. Furthermore, this disclosure provides a connecting structure comprising an adhesive layer formed from the urethane resin-forming composition and a method for producing the same.

[0009] Preferred embodiments of this disclosure are described in detail below.

[0010] (Urethane resin forming composition) The urethane resin forming composition of this embodiment comprises a main component (A) and a curing agent (B).

[0011] In this embodiment, the main component (A) contains a polyisocyanate (A-1) and an isocyanate-terminated prepolymer (A-2), which is a reaction product of polyisocyanate (A-1) and polyol (x-1). The curing agent (B) contains a polyol (B-1) having a tertiary amino group and three or more hydroxyl groups, and a polyol (B-2). Polyol (x-1) and polyol (B-2) are each independently polyester polyols or polycarbonate polyols, and the number average molecular weight of polyol (B-2) is 2000 or less.

[0012] The urethane resin-forming composition of this embodiment exhibits a short reaction time between mixing the main component (A) and the curing agent (B) and allowing them to react, resulting in the development of sufficient adhesive strength. For this reason, the urethane resin-forming composition of this embodiment can be suitably used as an adhesive (particularly a structural adhesive).

[0013] The urethane resin-forming composition of this embodiment may be a two-component type in which the main component (A) and the curing agent (B) exist separately, a one-component type in which the main component (A) and the curing agent (B) are combined, or a multi-component type with three or more components. When a one-component type requires long-term storage, it is preferable to employ known means to prevent the functional groups from reacting in the one-component state, such as blocking the isocyanate groups in the main component (A). When the urethane resin-forming composition is a two-component or multi-component type, it may comprise, for example, a first component containing the main component (A) and a second component containing the curing agent (B). In the case of one-component, two-component, and multi-component types, each component may be in a liquid state at the time of use, and may, for example, be solid at room temperature (23°C).

[0014] (Main component (A)) Main component (A) is a compound having two or more isocyanate groups and forming a urethane resin through reaction with the curing agent (B). Main component (A) contains polyisocyanate (A-1) and isocyanate group-terminated prepolymer (A-2), which is a reaction product of polyisocyanate (A-1) and polyol (x-1).

[0015] The main component (A) may, for example, contain a reaction product of component (a) which contains a polyisocyanate (A-1) and a polyol (x-1), and the reaction product may contain unreacted polyisocyanate (A-1).

[0016] Polyisocyanate (A-1) can be any compound having multiple isocyanate groups. Main component (A) may contain only one type of polyisocyanate (A-1), or it may contain two or more types.

[0017] The number of isocyanate groups in polyisocyanate (A-1) may be, for example, 2 to 5, 2 to 4 or 2 to 3, or 2. Polyisocyanate (A-1) may be, for example, a compound having two isocyanate groups (diisocyanate).

[0018] Examples of polyisocyanates (A-1) include aromatic polyisocyanates, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. These can be used individually or in combination of two or more. Among these, aromatic polyisocyanates are preferred from the viewpoint of reactivity, viscosity, etc.

[0019] Aromatic polyisocyanates are compounds that have an aromatic ring and multiple isocyanate groups bonded to the aromatic ring. Aromatic polyisocyanates may have multiple aromatic rings. When an aromatic polyisocyanate has multiple aromatic rings, the multiple isocyanate groups may be bonded to the same aromatic ring or to different aromatic rings.

[0020] Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate / 2,6-tolylene diisocyanate mixture, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate mixture, 2,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate mixture, 2,2'-diphenylmethane diisocyanate / 2,4'-diphenylmethane diisocyanate / Examples include 4,4'-diphenylmethane diisocyanate mixtures, m-xylylene diisocyanate, p-xylylene diisocyanate, 4,4'-diphenyl ether 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.

[0021] Aromatic aliphatic polyisocyanates are compounds having an aromatic ring and an aliphatic hydrocarbon group bonded to the aromatic ring, and having multiple isocyanate groups bonded to the aliphatic hydrocarbon group. Aromatic aliphatic polyisocyanates may have multiple aromatic rings and may have multiple aliphatic hydrocarbon groups. The multiple aliphatic hydrocarbon groups may be bonded to the same aromatic ring or to different aromatic rings. The multiple isocyanate groups may be bonded to the same aliphatic hydrocarbon group or to different aliphatic hydrocarbon groups.

[0022] Examples of aromatic aliphatic polyisocyanates include 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, a mixture of 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene, 1,4-bis(1-isocyanato-1-methylethyl)benzene, a mixture of 1,3-bis(1-isocyanato-1-methylethyl)benzene and 1,4-bis(1-isocyanato-1-methylethyl)benzene, and ω,ω'-diisocyanato-1,4-diethylbenzene.

[0023] Aliphatic polyisocyanates are compounds having an aliphatic hydrocarbon group (e.g., an alkane) from which several hydrogen atoms have been removed, and having multiple isocyanate groups bonded to the aliphatic hydrocarbon group. Aliphatic polyisocyanates may have multiple aliphatic hydrocarbon groups. The multiple isocyanate groups may be bonded to the same aliphatic hydrocarbon group or to different aliphatic hydrocarbon groups. Aliphatic polyisocyanates may be compounds that do not have aromatic rings or alicyclic groups.

[0024] 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-trimethylhexamethylene diisocyanate. Examples 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.

[0025] Alicyclic polyisocyanates are compounds having an alicyclic group formed by removing several hydrogen atoms from an alicyclic hydrocarbon, and having multiple isocyanate groups bonded to the alicyclic group. Alicyclic polyisocyanates may have multiple alicyclic groups. The multiple isocyanate groups may be bonded to the same alicyclic group or to different alicyclic groups. The isocyanate groups may be directly bonded to the ring in the alicyclic group, or they may be bonded to an aliphatic hydrocarbon group bonded to the ring.

[0026] Examples of alicyclic polyisocyanates include isophorone diisocyanate, cyclohexane diisocyanate, bis(isocyanate-methyl)cyclohexane, dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, dicyclohexyldimethylmethane diisocyanate, 2,2'-dimethyldicyclohexylmethane diisocyanate, bis(4-isocyanate-n-butylidene)pentaerythritol, and hydrogenated dimer acid diisocyanate. , 2-isocyanatemethyl-3-(3-isocyanatetopropyl)-5-isocyanatemethyl-bicyclo[2.2.1]-heptane, 2-isocyanatemethyl-3-(3-isocyanatetopropyl)-6-isocyanatemethyl-bicyclo[2.2.1]-heptane, 2-isocyanatemethyl-2-(3-isocyanatetopropyl)-5-isocyanatemethyl-bicyclo[2.2.1]-heptane, 2-isocyanatemethyl-2-(3-isocyanatepropyl (L)-6-isocyanatemethyl-bicyclo[2.2.1]-heptane,2-isocyanatemethyl-3-(3-isocyanatetopropyl)-5-(2-isocyanateethyl)-bicyclo-[2.2.1]-heptane,2-isocyanatemethyl-3-(3-isocyanatetopropyl)-6-(2-isocyanateethyl)-bicyclo-[2.2.1]-heptane,2-isocyanatemethyl-2-(3-isocyanatetopropyl)-5-(2-isocyanateethyl) Examples include bicyclo-[2.2.1]-heptane, 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 tetramethylxylene diisocyanate.

[0027] The isocyanate-terminated prepolymer (A-2) is a reaction product of polyisocyanate (A-1) and polyol (x-1). The isocyanate-terminated prepolymer (A-2) has constituent units derived from polyol (x-1) and terminal portions derived from polyisocyanate (A-1). The isocyanate-terminated prepolymer (A-2) may further have constituent units derived from polyisocyanate (A-1).

[0028] Examples of polyisocyanates (A-1) in isocyanate-terminated prepolymers (A-2) include those described above.

[0029] Polyol (x-1) is a compound having multiple hydroxyl groups. In this embodiment, polyol (x-1) is a polyester polyol or a polycarbonate polyol.

[0030] Examples of polyester polyols include condensation polymers of one or more polyols (x-1-1) and one or more dicarboxylic acids (x-1-2).

[0031] The polyol (x-1-1) may be, for example, 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, dimer acid diol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, etc.

[0032] As for the polyol (x-1-1), an alkanediol is preferred from the viewpoint that the main component (A) is easily liquid at room temperature.

[0033] The number of carbon atoms in the alkanediol may be, for example, two or more, three or more, or four or more. The number of carbon atoms in the alkanediol may be, for example, 12 or less, 11 or less, or 10 or less.

[0034] The alkanediol may be a linear alkanediol or a branched alkanediol. Two or more types of alkanediols may be used; for example, two or more linear alkanediols may be used, two or more branched alkanediols may be used, or one or more linear alkanediols and one or more branched alkanediols may be used.

[0035] Examples of alkanediols 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, and the like.

[0036] The dicarboxylic acid (x-1-2) may be, for example, 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, fumaric acid, etc.

[0037] Alkane dicarboxylic acid is preferred as the dicarboxylic acid (x-1-2) from the viewpoint that the main component (A) is easily liquid at room temperature.

[0038] The number of carbon atoms in the alkanedicarboxylic acid may be, for example, 2 or more, and may also be 3 or more, or 4 or more. The number of carbon atoms in the alkanedicarboxylic acid may be, for example, 12 or less, and may also be 11 or less, or 10 or less. From these perspectives, the number of carbon atoms in the alkanedicarboxylic acid may be, for example, 2 to 12, 2 to 11, 2 to 10, 3 to 12, 3 to 11, 3 to 10, 4 to 12, 4 to 11, or 4 to 10.

[0039] Examples of the alkanedicarboxylic acid include succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

[0040] Examples of the polyester polyol also include a polymer of a cyclic ester (x-1-3) obtained by using a polyol (x-1-1) as an initiator.

[0041] Examples of the cyclic ester (x-1-3) include caprolactone, butyrolactone, valerolactone, glycolide, and lactide.

[0042] Examples of the polycarbonate polyol include a condensation polymer of one or more types of the polyol (x-1-1) and carbonates (x-1-4).

[0043] Examples of the polyol (x-1-1) include the same ones as described above. The polyol (x-1-1) may be used alone as one type, or may be used in combination of two or more types.

[0044] The carbonates (x-1-4) are not particularly limited as long as they are carbonates that can undergo condensation polymerization with the polyol (x-1-1), and examples thereof may include 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, and diindanyl carbonate.

[0045] The number-average molecular weight of polyol (x-1) may be, for example, 500 or more, and from the viewpoint of the toughness of the cured product, it may be 700 or more, 800 or more, or 900 or more. Also, the number-average molecular weight of polyol (x-1) may be, for example, 10,000 or less, and from the viewpoint of the miscibility between the main component (A) and the curing agent (B), it may be 8,000 or less, 6,000 or less, or 4,000 or less. From these perspectives, the number-average molecular weight of polyol(x-1) may be, for example, 500-10000, 500-8000, 500-6000, 500-4000, 700-10000, 700-8000, 700-6000, 700-4000, 800-10000, 800-8000, 800-6000, 800-4000, 900-10000, 900-8000, 900-6000, or 900-4000.

[0046] The number-average molecular weight of polyol (x-1) is preferably greater than the number-average molecular weight of polyol (B-2) described below. The difference between the number-average molecular weight of polyol (x-1) and polyol (B-2) may be, for example, 50 or more, and may be 100 or more, 200 or more, or 300 or more. Also, the difference between the number-average molecular weight of polyol (x-1) and polyol (B-2) may be, for example, 9000 or less, and may be 7000 or less, 5000 or less, or 3000 or less. From these perspectives, the difference between the number-average molecular weight of polyol (x-1) and the number-average molecular weight of polyol (B-2) may be, for example, 50-9000, 50-7000, 50-5000, 50-3000, 100-9000, 100-7000, 100-5000, 100-3000, 200-9000, 200-7000, 200-5000, 200-3000, 300-9000, 300-7000, 300-5000, or 300-3000.

[0047] The number-average molecular weight of polyol (x-1) is the value calculated from the hydroxyl value measured according to the method in accordance with JIS K 0070-1992.

[0048] The main component (A) may, for example, include the reaction product of component (a) which contains a polyisocyanate (A-1) and a polyol (x-1). The reaction product of component (a) includes unreacted polyisocyanate (A-1) and an isocyanate-terminated prepolymer (A-2).

[0049] The content of polyisocyanate (A-1) in component (a) may be, for example, 10% by mass or more, 35% by mass or more, 55% by mass or more, or 75% by mass or more, based on the total amount of component (a). Alternatively, the content of polyisocyanate (A-1) in component (a) may be, for example, 96% by mass or less, 94% by mass or less, 92% by mass or less, or 90% by mass or less, based on the total amount of component (a). From these viewpoints, the content of polyisocyanate (A-1) in component (a) may be, for example, 10-96% by mass, 10-94% by mass, 10-92% by mass, 10-90% by mass, 35-96% by mass, 35-94% by mass, 35-92% by mass, 35-90% by mass, 55-96% by mass, 55-94% by mass, 55-92% by mass, 55-90% by mass, 75-96% by mass, 75-94% by mass, 75-92% by mass, or 75-90% by mass, based on the total amount of component (a).

[0050] In component (a), the ratio (NCO / OH) of the total number of isocyanate groups in polyisocyanate (A-1) to the total number of hydroxyl groups in polyol (x-1) may be, for example, 2 or more, and may be 5 or more, 10 or more, or 15 or more. Also, the above ratio (NCO / OH) may be, for example, 150 or less, and may be 130 or less, 120 or less, or 110 or less. From these viewpoints, the above ratio (NCO / OH) may be, for example, 2 to 150, 2 to 130, 2 to 120, 2 to 110, 5 to 150, 5 to 130, 5 to 120, 5 to 110, 10 to 150, 10 to 130, 10 to 120, 10 to 110, 15 to 150, 15 to 130, 15 to 120, or 15 to 110.

[0051] The reaction conditions for component (a) are not particularly limited, and any conditions that allow the isocyanate group and hydroxyl group in component (a) to react and form a urethane bond are acceptable. The reaction temperature for component (a) may be, for example, 40 to 100°C, and the reaction time for component (a) may be, for example, 30 minutes to 6 hours.

[0052] The urethane group concentration in the main component (A) (i.e., the amount of urethane groups per unit mass of resin components in the main component (A)) may be, for example, 60 mmol / kg or more, and from the viewpoint of filler dispersibility, it may be 70 mmol / kg or more, 80 mmol / kg or more, or 100 mmol / kg or more. Furthermore, the urethane group concentration in the main component (A) may be, for example, 450 mmol / kg or less, and from the viewpoint of miscibility between the main component (A) and the curing agent (B), it may be 400 mmol / kg or less, 350 mmol / kg or less, or 300 mmol / kg or less. From these viewpoints, the concentration of urethane groups in the main component (A) may be, for example, 60-450 mmol / kg, 60-400 mmol / kg, 60-350 mmol / kg, 60-300 mmol / kg, 70-450 mmol / kg, 70-400 mmol / kg, 70-350 mmol / kg, 70-300 mmol / kg, 80-450 mmol / kg, 80-400 mmol / kg, 80-350 mmol / kg, 80-300 mmol / kg, 100-450 mmol / kg, 100-400 mmol / kg, 100-350 mmol / kg, or 100-300 mmol / kg.

[0053] The main component (A) may or may not further contain other polymerizable compounds other than polyisocyanate (A-1) and isocyanate-terminated prepolymer (A-2). Examples of other polymerizable compounds include acrylic acid esters and methacrylic acid esters.

[0054] The content of other polymerizable compounds may be, for example, 20% by mass or less on a basis of the total amount of main component (A), 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or even 0% by mass. That is, the total content of polyisocyanate (A-1) and isocyanate group-terminated prepolymer (A-2) in main component (A) may be, for example, 80% by mass or more on a basis of the total amount of main component (A), 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more, or even 100% by mass.

[0055] The main component (A) is preferably in liquid form at 25°C and 1 atmosphere.

[0056] (Curing agent (B)) The curing agent (B) is a compound having two or more hydroxyl groups and forming a urethane resin through reaction with the main component (A). The curing agent (B) contains a polyol (B-1) having a tertiary amino group and three or more hydroxyl groups, and a polyol (B-2).

[0057] Polyol (B-1) has a tertiary amino group and therefore functions as a catalyst to promote the reaction between the main component (A) and the curing agent (B). Furthermore, because polyol (B-1) has three or more hydroxyl groups, it also functions as a crosslinking agent to introduce a crosslinked structure into the urethane resin.

[0058] Polyol (B-1) is, for example, a -R atom attached to the nitrogen atom. １ A structure in which three groups represented by OH are bonded together (for example, N(R) １ OH) ３ ) may be a compound having R. １ It is a divalent group that links a nitrogen atom (N) and a hydroxyl group (OH). １ These may be the same or different.

[0059] R １ Examples include alkanediyl groups, arylene groups, and divalent groups formed by combining alkanediyl and arylene groups.

[0060] R １The alkanediyl group in may be linear or branched. The number of carbon atoms in the alkanediyl group may, for example, be 2 or more, or may be 3 or more. The number of carbon atoms in the alkanediyl group may, for example, be 6 or less, may be 5 or less, or may be 4 or less. From these viewpoints, the number of carbon atoms in the alkanediyl group may, for example, be 2 to 6, 2 to 5, 2 to 4, 3 to 6, 3 to 5, or 3 to 4.

[0061] R １ Examples of the alkanediyl group in include ethanediyl group, 1,2-propanediyl group, 1,3-propanediyl group, butanediyl group, pentanediyl group, hexanediyl group, and the like.

[0062] R １ Examples of the arylene group in include phenylene group, tolylene group, and the like.

[0063] R １ is preferably an alkanediyl group from the viewpoint that the curing agent (B) tends to be liquid at ordinary temperature.

[0064] Three R １ may be the same or different.

[0065] Examples of the polyol (B-1) include triethanolamine, triisopropanolamine, N,N-bishydroxypropyl-N-hydroxyethylamine, N,N-bishydroxyethylisopropanolamine, modified ethylenediamine propylene oxide, and the like.

[0066] The polyol (B-2) is a polyester polyol or a polycarbonate polyol.

[0067] As the polyester polyol in the polyol (B-2), the same ones as the polyester polyol in the above-mentioned polyol (x-1) can be exemplified. Further, as the polycarbonate polyol in the polyol (B-2), the same ones as the polycarbonate polyol in the above-mentioned polyol (x-1) can be exemplified.

[0068] In this embodiment, the number-average molecular weight of polyol (B-2) is 2000 or less. Having a number-average molecular weight of 2000 or less of polyol (B-2) results in better miscibility between the main component (A) and the curing agent (B).

[0069] The number-average molecular weight of polyol (B-2) may be, for example, 200 or more, and from the viewpoint of the toughness of the cured product, it may be 300 or more, or 400 or more. Alternatively, the number-average molecular weight of polyol (B-2) may be 2000 or less, and from the viewpoint of obtaining the above-mentioned effects more significantly, it may be 1800 or less, 1600 or less, 1400 or less, or 1200 or less. From these perspectives, the number-average molecular weight of polyol (B-2) may be, for example, 200-2000, 200-1800, 200-1600, 200-1400, 200-1200, 300-2000, 300-1800, 300-1600, 300-1400, 300-1200, 400-2000, 400-1800, 400-1600, 400-1400, or 400-1200.

[0070] The number-average molecular weight of polyol (B-2) is preferably smaller than the number-average molecular weight of polyol (x-1) described above. The difference between the number-average molecular weight of polyol (x-1) and the number-average molecular weight of polyol (B-2) may be, for example, 50 or more, and may be 100 or more, 150 or more, or 200 or more. Also, the difference between the number-average molecular weight of polyol (x-1) and the number-average molecular weight of polyol (B-2) may be, for example, 9000 or less, and may be 7000 or less, 5000 or less, or 3000 or less. From these perspectives, the difference between the number-average molecular weight of polyol (x-1) and the number-average molecular weight of polyol (B-2) may be, for example, 50-9000, 50-7000, 50-5000, 50-3000, 100-9000, 100-7000, 100-5000, 100-3000, 150-9000, 150-7000, 150-5000, 150-3000, 200-9000, 200-7000, 200-5000, or 200-3000.

[0071] The number-average molecular weight of polyol (B-2) is the value calculated from the hydroxyl value measured according to the method in accordance with JIS K 0070-1992.

[0072] The polyol (B-1) content in the curing agent (B) may be, for example, 10% by mass or more based on the total amount of curing agent (B), and from the viewpoint of shortening the time until sufficient adhesive strength is achieved, it may be 14% by mass or more, 16% by mass or more, or 20% by mass or more. In addition, the polyol (B-1) content in the curing agent (B) may be, for example, 60% by mass or less based on the total amount of curing agent (B), and from the viewpoint of pot life, it may be 55% by mass or less, 50% by mass or less, or 45% by mass or less. From these viewpoints, the content of polyol (B-1) in curing agent (B) may be, for example, 10-60% by mass, 10-55% by mass, 10-50% by mass, 10-45% by mass, 14-60% by mass, 14-55% by mass, 14-50% by mass, 14-45% by mass, 16-60% by mass, 16-55% by mass, 16-50% by mass, 16-45% by mass, 20-60% by mass, 20-55% by mass, 20-50% by mass, or 20-45% by mass, based on the total amount of curing agent (B).

[0073] The polyol (B-2) content in the curing agent (B) may be, for example, 30% by mass or more based on the total amount of curing agent (B), and from the viewpoint of the toughness of the cured product, it may be 40% by mass or more, 45% by mass or more, or 50% by mass or more. Alternatively, the polyol (B-2) content in the curing agent (B) may be, for example, 90% by mass or less based on the total amount of curing agent (B), and from the viewpoint of the strength of the cured product, it may be 85% by mass or less, 80% by mass or less, or 75% by mass or less. From these viewpoints, the content of polyol (B-2) in curing agent (B) may be, for example, 30-90% by mass, 30-85% by mass, 30-80% by mass, 30-75% by mass, 40-90% by mass, 40-85% by mass, 40-80% by mass, 40-75% by mass, 45-90% by mass, 45-85% by mass, 45-80% by mass, 45-75% by mass, 50-90% by mass, 50-85% by mass, 50-80% by mass, or 50-75% by mass, based on the total amount of curing agent (B).

[0074] The curing agent (B) may or may not contain other curing agents other than polyol (B-1) and polyol (B-2).

[0075] The content of other curing agents may be, for example, 20% by mass or less based on the total amount of curing agent (B), 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or even 0% by mass. That is, the total content of polyol (B-1) and polyol (B-2) in curing agent (B) may be, for example, 80% by mass or more based on the total amount of curing agent (B), 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more, or even 100% by mass.

[0076] The amine concentration in the curing agent (B) (i.e., the content of tertiary amino groups per unit mass of the resin component in the curing agent (B)) may be, for example, 200 mmol / kg or more, and from the viewpoint of shortening the time until sufficient adhesive strength is achieved, it may be 600 mmol / kg or more, 800 mmol / kg or more, or 1000 mmol / kg or more. Alternatively, the amine concentration in the curing agent (B) may be, for example, 2600 mmol / kg or less, and from the viewpoint of pot life, it may be 2400 mmol / kg or less, 2200 mmol / kg or less, or 2000 mmol / kg or less. From these viewpoints, the amine concentration in the curing agent (B) may be, for example, 200-2600 mmol / kg, 200-2400 mmol / kg, 200-2200 mmol / kg, 200-2000 mmol / kg, 600-2600 mmol / kg, 600-2400 mmol / kg, 600-2200 mmol / kg, 600-2000 mmol / kg, 800-2600 mmol / kg, 800-2400 mmol / kg, 800-2200 mmol / kg, 800-2000 mmol / kg, 1000-2600 mmol / kg, 1000-2400 mmol / kg, 1000-2200 mmol / kg, or 1000-2000 mmol / kg.

[0077] The curing agent (B) is preferably liquid at 25°C and 1 atmosphere.

[0078] The urethane resin-forming composition of this embodiment may further contain a filler (C).

[0079] When the urethane resin-forming composition is a two-component type, filler (C) may be included in the first component together with the main component (A), or in the second component together with the curing agent (B). Alternatively, filler (C) may be divided into filler (C1) and filler (C2) and blended into the first and second components, respectively. That is, the urethane resin-forming composition may, for example, include a first component containing the main component (A) and filler (C), and a second component containing the curing agent (B). Alternatively, the urethane resin-forming composition may include a first component containing the main component (A), and a second component containing the curing agent (B) and filler (C). Alternatively, the urethane resin-forming composition may include a first component containing the main component (A) and filler (C1), and a second component containing the curing agent (B) and filler (C2).

[0080] Examples of filler (C) include known fillers. Filler (C) may be, for example, an inorganic filler or an organic filler, and is preferably an inorganic filler. Filler (C) can be used alone or in combination of two or more types.

[0081] Examples of inorganic fillers include talc, zeolite, silica, microballoons, clay, glass balloons, carbon black, and calcium carbonate. However, the inorganic fillers are not limited to these. They can be used individually or in combination of two or more.

[0082] Examples of organic fillers include polyamide particles, acrylic particles, carbon nanotubes, starch, natural organic fibers, and synthetic fibers.

[0083] The content of filler (C) may be, for example, 10 parts by mass or more per 100 parts by mass of the total of the main component (A) and the hardener (B), and from the viewpoint of suppressing dripping, it may be 15 parts by mass or more, 20 parts by mass or more, or 25 parts by mass or more. Alternatively, the content of filler (C) may be, for example, 70 parts by mass or less per 100 parts by mass of the total of the main component (A) and the hardener (B), and from the viewpoint of adhesive strength and coating properties, it may be 60 parts by mass or less, 50 parts by mass or less, or 45 parts by mass or less. From these viewpoints, the content of filler (C) may be, for example, 10 to 70 parts by mass, 10 to 60 parts by mass, 10 to 50 parts by mass, 10 to 45 parts by mass, 15 to 70 parts by mass, 15 to 60 parts by mass, 15 to 50 parts by mass, 15 to 45 parts by mass, 20 to 70 parts by mass, 20 to 60 parts by mass, 20 to 50 parts by mass, 20 to 45 parts by mass, 25 to 70 parts by mass, 25 to 60 parts by mass, 25 to 50 parts by mass, or 25 to 45 parts by mass, relative to 100 parts by mass of the total of the main component (A) and the hardener (B).

[0084] The urethane resin-forming composition of this embodiment may further contain other components besides the main component (A), the curing agent (B), and the filler (C).

[0085] Other components include, for example, solvents, colorants, antistatic agents, preservatives, defoamers, hydrolysis inhibitors, and catalysts.

[0086] Other components may be included in the first component together with the main component (A), or in the second component together with the hardener (B), or they may be divided and formulated into the first and second components.

[0087] The content of other components may be, for example, 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, 3 parts by mass or less, or 1 part by mass or less, or even 0 parts by mass, based on 100 parts by mass of the total of the main component (A) and the hardening agent (B).

[0088] The urethane resin-forming composition may be substantially solvent-free, i.e., solvent-free. When the urethane resin-forming composition is solvent-free, the solvent content may be, for example, 1 part by mass or less, 0.5 parts by mass or less, or 0.1 parts by mass or less, or 0 parts by mass, based on 100 parts by mass of the total of the main component (A) and the curing agent (B).

[0089] The urethane resin-forming composition of this embodiment may be a two-component type comprising a first component containing a main component (A) and a second component containing a curing agent (B). In this case, by mixing the first component and the second component, the main component (A) and the curing agent (B) are reacted to form a urethane resin.

[0090] The urethane resin-forming composition of this embodiment can form a urethane resin by mixing the main component (A) and the curing agent (B) (for example, by mixing the first component and the second component) and reacting the main component (A) and the curing agent (B).

[0091] The urethane group concentration in the urethane resin (i.e., the content of urethane groups per unit mass of the urethane resin) may be, for example, 2000 mmol / kg or more, and from the viewpoint of the strength of the cured product, it may be 2400 mmol / kg or more, 2600 mmol / kg or more, or 3000 mmol / kg or more. The urethane group concentration in the urethane resin may be, for example, 4600 mmol / kg or less, and from the viewpoint of the toughness of the cured product, it may be 4400 mmol / kg or less, 4200 mmol / kg or less, or 4000 mmol / kg or less. From these viewpoints, the concentration of urethane groups in the urethane resin may be, for example, 2000-4600 mmol / kg, 2000-4400 mmol / kg, 2000-4200 mmol / kg, 2000-4000 mmol / kg, 2400-4600 mmol / kg, 2400-4400 mmol / kg, 2400-4200 mmol / kg, 2400-4000 mmol / kg, 2600-4600 mmol / kg, 2600-4400 mmol / kg, 2600-4200 mmol / kg, 2600-4000 mmol / kg, 3000-4600 mmol / kg, 3000-4400 mmol / kg, 3000-4200 mmol / kg, or 3000-4000 mmol / kg.

[0092] The amine concentration in the urethane resin (i.e., the content of tertiary amino groups per unit mass of the urethane resin) may be, for example, 100 mmol / kg or more, and from the viewpoint of shortening the time until sufficient adhesive strength is achieved, it may be 300 mmol / kg or more, 400 mmol / kg or more, or 500 mmol / kg or more. Alternatively, the amine concentration in the urethane resin may be, for example, 1300 mmol / kg or less, and from the viewpoint of pot life, it may be 1200 mmol / kg or less, 1100 mmol / kg or less, or 1000 mmol / kg or less. From these viewpoints, the amine concentration in the urethane resin may be, for example, 100-1300 mmol / kg, 100-1200 mmol / kg, 100-1100 mmol / kg, 100-1000 mmol / kg, 300-1300 mmol / kg, 300-1200 mmol / kg, 300-1100 mmol / kg, 300-1000 mmol / kg, 400-1300 mmol / kg, 400-1200 mmol / kg, 400-1100 mmol / kg, 400-1000 mmol / kg, 500-1300 mmol / kg, 500-1200 mmol / kg, 500-1100 mmol / kg, or 500-1000 mmol / kg.

[0093] The compositions of the main component (A) and the curing agent (B) may be adjusted as appropriate so that the urethane group concentration and / or amine concentration of the formed urethane resin are within the range described above.

[0094] In the urethane resin-forming composition of this embodiment, the ratio (OH / NCO) of the total number of hydroxyl groups in the curing agent (B) to the total number of isocyanate groups in the main component (A) may be, for example, 0.75 or more, and from the viewpoint of the toughness of the cured product, it may be 0.81 or more, 0.83 or more, or 0.85 or more. Alternatively, the above ratio (OH / NCO) may be, for example, 1.25 or less, and from the viewpoint of the strength of the cured product, it may be 1.21 or less, 1.18 or less, or 1.15 or less. From these perspectives, the above ratio (OH / NCO) may be, for example, 0.75-1.25, 0.75-1.21, 0.75-1.18, 0.75-1.15, 0.81-1.25, 0.81-1.21, 0.81-1.18, 0.81-1.15, 0.83-1.25, 0.83-1.21, 0.83-1.18, 0.83-1.15, 0.85-1.25, 0.85-1.21, 0.85-1.18, or 0.85-1.15.

[0095] The means for mixing the main component (A) and the hardener (B) (the means for mixing the first component and the second component) are not particularly limited. For example, they may be mixed manually with a spatula, or they may be mixed using a mechanical rotary mixer, a static mixer, or the like.

[0096] The urethane resin-forming composition of this embodiment can be suitably used as an adhesive.

[0097] (Adhesive) The adhesive of this embodiment comprises a main component (A) and a curing agent (B). The adhesive of this embodiment may be an adhesive made of the urethane resin-forming composition described above.

[0098] The adhesive of this embodiment may be a two-component adhesive comprising a first component containing a main component (A) and a second component containing a curing agent (B).

[0099] The adhesive of this embodiment may further contain filler (C). Filler (C) may be incorporated into the first component or the second component, or it may be divided into filler (C1) and filler (C2) and incorporated into both the first and second components.

[0100] In other words, the adhesive of this embodiment may, for example, comprise a first agent containing a main agent (A) and a filler (C), and a second agent containing a curing agent (B); or a first agent containing a main agent (A) and a second agent containing a curing agent (B) and a filler (C); or a first agent containing a main agent (A) and a filler (C1), and a second agent containing a curing agent (B) and a filler (C2).

[0101] The adhesive of this embodiment can be suitably used as a structural adhesive.

[0102] The adhesive of this embodiment can be suitably used, for example, for bonding dissimilar materials together.

[0103] Application fields of the adhesive of this embodiment include, for example, the automotive, display, recording medium, electronic materials, battery, optical components, construction, electronic equipment, and aerospace industries.

[0104] In the automotive field, for example, it can be used in structural parts, switch parts, headlights, engine components, electrical components, drive engines, and brake fluid tanks. In the display field, for example, it can be used in liquid crystal displays, organic electroluminescent displays, and light-emitting diode displays. In the recording medium field, for example, it can be used in video discs, CDs, DVDs, MDs, pickup lenses, VCM magnets, spindle motors, hard disk peripheral components, and Blu-ray discs.

[0105] In the field of electronic materials, for example, it can be used in electronic components, electrical circuits, electrical contacts, or semiconductor devices. More specifically, these applications include encapsulating materials, die bonding agents, conductive adhesives, anisotropic conductive adhesives, and interlayer adhesives for multilayer substrates, including build-up substrates. In the field of batteries, for example, it can be used 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, for example, it can be used in optical fiber materials around optical switches and optical connectors in optical communication systems, as well as in optical passive components, optical circuit components, and around optoelectronic integrated circuits. In the field of electronic equipment, for example, it can be used in camera modules.

[0106] The adhesive of this embodiment can be used particularly suitably as a structural adhesive for automobiles.

[0107] (Connecting structure) The connecting structure of this embodiment comprises a first member, a second member, and an adhesive layer that bonds the first member and the second member together.

[0108] The first member and the second member may be bonded together via an adhesive layer, with the adhesive surface of the first member and the adhesive surface of the second member being bonded together.

[0109] The adhesive layer may consist of a cured product of the urethane resin-forming composition described above, or a cured product of the adhesive described above.

[0110] The bonding surfaces of the first member and the second member may be made of different materials. Examples of materials that make up the bonding surfaces of the first member and the second member include metals such as aluminum, iron, and titanium, as well as plastics, fiber-reinforced resins, and the like.

[0111] The connecting structure of this embodiment can be manufactured, for example, by a manufacturing method that includes the steps of: preparing the above-mentioned urethane resin-forming composition (or the above-mentioned adhesive); placing a mixture of the main agent (A) and the curing agent (B) (or a mixture of the first agent and the second agent) between the first member and the second member; and curing the mixture to form an adhesive layer.

[0112] The conditions for curing the mixture are not particularly limited and may be, for example, 10°C to 200°C for 1 minute to 72 hours.

[0113] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above.

[0114] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0115] <Raw Materials> The following raw materials were used to carry out the examples and comparative examples. - "NM" (Millionate NM (manufactured by Tosoh Corporation), 4,4'-diphenylmethane diisocyanate / 2,4'-diphenylmethane diisocyanate mixture, average molecular weight 250, f=2) - "PCD-3000" (Polycarbonate polyol (manufactured by Tosoh Corporation, Nipponran® 968), average molecular weight 3000, f=2) - "PCD-1000" (Polycarbonate polyol (manufactured by Tosoh Corporation, Nipponran® 965), average molecular weight 1000, f=2) - "PCD-500" (Polycarbonate polyol (manufactured by Tosoh Corporation, Nipponran® 976), average molecular weight 500, f=2) - "MA-170" (Leocon MA-170 (manufactured by Lion Specialty Chemicals), N,N-bishydroxypropyl-N-hydroxyethylamine, average molecular weight 175, f=3) • "Zeolite" (Zeolam® A-3 (manufactured by Tosoh Corporation)) • "Talc" (Talc (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.))

[0116] (Example 1) The main component raw materials were added to a 2 L stirring container filled with nitrogen according to the formulation shown in Table 1 and stirred. Then, the temperature inside the stirring container was maintained at 70-80°C and stirred for about 2-5 hours to allow the urethane reaction to proceed and obtain the main component (A). In addition, the hardening agent raw materials were added to a 2 L stirring container filled with nitrogen according to the formulation shown in Table 1 and stirred for about 1-3 hours while maintaining the temperature inside the stirring container at 70-80°C to obtain the hardening agent (B).

[0117] Next, filler (C1) shown in Table 1 was added to the main component (A), and the mixture was obtained using a rotary-rotating agitator (product name: Kakuhunter, manufactured by Shashin Kagaku Co., Ltd.). Then, filler (C2) shown in Table 1 was added to the hardener (B), and the mixture was obtained using a rotary-rotating agitator (product name: Kakuhunter, manufactured by Shashin Kagaku Co., Ltd.).

[0118] Adhesion test specimens were prepared and evaluated using the first and second agents according to the following method. The results are shown in Table 1.

[0119] <Preparation and Evaluation of Adhesion Test Specimens> The first and second components were mixed uniformly using a stainless steel spatula to prepare the adhesive. The adhesive was applied to the surface of two aluminum plates (100 mm long x 25 mm wide x 1 mm thick, A6061P, Ti-Zr treated) and bonded together so that the overlapping area of ​​the aluminum plates was 12.5 mm long x 25 mm wide. The plates were left at 23°C for 3 hours to obtain adhesion test specimens. The thickness of the adhesive layer was adjusted to 0.25 mm using glass beads. The tensile shear strength (MPa) of the bonded portion of the prepared adhesion test specimens was measured using a tensile testing machine (product name: Autocom Universal Tester AC-10kN-C, manufactured by TSE Corporation). This measurement was performed in accordance with the tensile shear bond strength of adhesives specified in JIS K6850:1999. The measurement conditions were a temperature of 23°C, a chuck distance of 111.5 mm, and a test speed of 10 mm / min.

[0120] Next, adhesive test specimens were prepared by varying the time they were left at 23°C to 5 hours, 8 hours, and 24 hours, and the tensile shear strength (MPa) of the bonded area was measured using the same method as described above. Furthermore, the tensile shear strength after 24 hours was set as 100%, and the rate of tensile shear strength development in each adhesive test specimen was calculated.

[0121] (Examples 2-3) The first and second components were obtained in the same manner as in Example 1, except that the formulations of the main component (A) and the hardening agent (B) were changed as shown in Table 1. Using the obtained first and second components, adhesion test specimens were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0122] (Comparative Example 1) The first and second components were obtained in the same manner as in Example 1, except that the formulations of the main component (A) and the curing agent (B) were changed as shown in Table 1. Using the obtained first and second components, adhesion test specimens were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0123]

Claims

1. A urethane resin-forming composition comprising a main component (A) and a curing agent (B), wherein the main component (A) contains a polyisocyanate (A-1) and an isocyanate-terminated prepolymer (A-2) which is a reaction product of the polyisocyanate (A-1) and a polyol (x-1), and the curing agent (B) contains a polyol (B-1) having a tertiary amino group and three or more hydroxyl groups, and a polyol (B-2), wherein the polyol (x-1) and the polyol (B-2) are each independently polyester polyols or polycarbonate polyols, and the number average molecular weight of the polyol (B-2) is 2000 or less.

2. The urethane resin-forming composition according to claim 1, wherein the polyol (x-1) is a polycarbonate polyol.

3. The urethane resin-forming composition according to claim 1, wherein the polyol (B-2) is a polycarbonate polyol.

4. The urethane resin-forming composition according to claim 1, wherein the number average molecular weight of the polyol (x-1) is 700 or more.

5. The urethane resin-forming composition according to claim 1, wherein the number-average molecular weight of the polyol (x-1) is greater than the number-average molecular weight of the polyol (B-2).

6. The urethane resin-forming composition according to claim 1, wherein the content of the polyol (B-1) in the curing agent (B) is 10% by mass or more based on the total amount of the curing agent (B).

7. The urethane resin-forming composition according to claim 1, wherein at least one of the main component (A) and the curing agent (B) is liquid at 25°C and 1 atm.

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

9. The urethane resin-forming composition according to claim 1, which is a two-component adhesive comprising a first agent containing the main agent (A) and a second agent containing the curing agent (B).

10. A urethane resin-forming composition according to claim 1, which is a structural adhesive.

11. A cured product of a urethane resin-forming composition according to any one of claims 1 to 10.

12. A method for producing a cured product, comprising the steps of: preparing a urethane resin-forming composition according to any one of claims 1 to 10; and curing a mixture of the main component (A) and the curing agent (B) to obtain a cured product containing urethane resin.

13. A connecting structure comprising: a first member; a second member; and an adhesive layer for bonding the first member and the second member, wherein the adhesive layer contains a cured product of a urethane resin-forming composition according to any one of claims 1 to 10.

14. The connecting structure according to claim 13, wherein the adhesive surface of the first member and the adhesive surface of the second member are formed of different materials.

15. A method for manufacturing a connecting structure comprising a first member, a second member, and an adhesive layer for bonding the first member and the second member, comprising the steps of: preparing a urethane resin-forming composition according to any one of claims 1 to 10; placing a mixture of the main agent (A) and the curing agent (B) between the first member and the second member; and curing the mixture to form the adhesive layer.

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