Structural polyurethane adhesive

Abstract

This polyurethane structural adhesive contains a polyisocyanate component and a polyol component. The polyisocyanate component contains: a first isocyanate component which contains a first isocyanate-terminated urethane prepolymer that is a reaction product of a first starting-material polyisocyanate that is composed of an aromatic polyisocyanate and a first starting-material polyol that contains a macro polyol: a second isocyanate component which contains a second isocyanate-terminated urethane prepolymer that is a reaction product of a second starting-material polyisocyanate that is composed of an aromatic aliphatic polyisocyanate and / or an aliphatic polyisocyanate and a second starting-material polyol that contains a polyether polyol having a number average molecular weight of 160 to 4900; and a third isocyanate component which contains a carbodiimide-modified aromatic polyisocyanate. The proportion of the second isocyanate component relative to the total mass of the first isocyanate component, the second isocyanate component and the third isocyanate component is 2% to 35% by mass.

Description

Technical Field

[0001] The present invention relates to a structural polyurethane adhesive.

Background Art

[0002] Conventionally, in a structure composed of a plurality of members, a structural adhesive has been used to bond each member. Examples of the structure include an automobile and a building. Examples of the structural adhesive include a two-component curable structural polyurethane adhesive containing a main agent (component 1) and a curing agent (component 2).

[0003] More specifically, the following formulation has been proposed as a structural polyurethane adhesive. That is, the curing agent (component 1) contains polyoxypropylene triol and 1,4-butanediol. The main agent (component 2) contains a polymer having a free isocyanate group and a carbodiimide of 4,4'-methylenediphenyl diisocyanate (MDI). The polymer having a free isocyanate group contains a reaction product of 4,4'-methylenediphenyl diisocyanate (MDI) with polyoxypropylene diol and polyoxypropylene polyoxyethylene triol (see, for example, Patent Document 1 (Example 1)).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, further improvement in adhesion characteristics is required for the structural polyurethane adhesive.

[0006] The present invention is a structural polyurethane adhesive having excellent adhesion characteristics.

Means for Solving the Problems

[0007] The present invention [1] contains a polyisocyanate component and a polyol component. The polyisocyanate component includes a first isocyanate component containing a first urethane prepolymer which is a reaction product of a first raw material polyisocyanate composed of an aromatic polyisocyanate and a first raw material polyol containing a macro polyol and having an isocyanate group terminal, a second isocyanate component containing a second urethane prepolymer which is a reaction product of a second raw material polyisocyanate composed of an araliphatic polyisocyanate and / or an aliphatic polyisocyanate and a second raw material polyol containing a polyether polyol having a number average molecular weight of 160 or more and 4900 or less, and a third isocyanate component containing a carbodiimide-modified product of an aromatic polyisocyanate. The proportion of the second isocyanate component is 2% by mass or more and 35% by mass or less with respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component, and includes a structural polyurethane adhesive.

[0008] The present invention [2] includes the structural polyurethane adhesive according to [1] above, wherein the second raw material polyisocyanate contains at least one selected from the group consisting of xylylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate), and bis(isocyanatomethyl)cyclohexane.

[0009] The present invention [3] includes the structural polyurethane adhesive according to [1] or [2] above, wherein the content ratio of the second raw material polyisocyanate is 1.0% by mass or less with respect to the total amount of the second isocyanate component.

[0010] The present invention [4] includes the structural polyurethane adhesive according to any one of [1] to [3] above, wherein the second raw material polyol contains a polyether polyol having an average hydroxyl group number of 2 or more and 3 or less.

[0011] The present invention [5] includes the structural polyurethane adhesive according to any one of [1] to [4] above, which is a two-component curable adhesive comprising a main agent containing the polyisocyanate component and a curing agent containing the polyol component.

[0012] The present invention [6] includes the structural polyurethane adhesive according to any one of [1] to [5] above, which is a solvent-free adhesive.

Advantages of the Invention

[0013] In the structural polyurethane adhesive of the present invention, the polyisocyanate component contains a first isocyanate component, a second isocyanate component, and a third isocyanate component. The first isocyanate component includes a first isocyanate group-terminated urethane prepolymer that is a reaction product of a first raw material polyisocyanate composed of an aromatic polyisocyanate and a first raw material polyol containing a macropolyol. The second isocyanate component includes a second isocyanate group-terminated urethane prepolymer that is a reaction product of a second raw material polyisocyanate composed of an aromatic aliphatic polyisocyanate and / or an aliphatic polyisocyanate, and a second raw material polyol containing a polyether polyol having a number average molecular weight of 160 or more and 4900 or less. Further, the third isocyanate component includes a carbodiimide-modified product of an aromatic polyisocyanate. And the ratio of the second isocyanate component is within a predetermined range with respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component. Therefore, the structural polyurethane adhesive of the present invention has excellent adhesive properties.

Embodiments for Carrying Out the Invention

[0014] The structural polyurethane adhesive of the present invention is a structural adhesive defined in JIS K 6800 (1985). Specifically, the structural polyurethane adhesive is a "reliable adhesive that can withstand large loads for a long period of time."

[0015] More specifically, the structural polyurethane adhesive contains a polyisocyanate component and a polyol component as essential components. The polyisocyanate component is a component containing free isocyanate groups. The polyol component is a component containing free hydroxyl groups.

[0016] Note that the structural polyurethane adhesive may be a one-component curing type adhesive in which the polyisocyanate component and the polyol component are pre-mixed. It may also be a two-component curing type adhesive comprising a main agent (liquid A) containing the polyisocyanate component and a curing agent (liquid B) containing the polyol component. In the two-component curing type adhesive, the separately prepared main agent and curing agent are mixed at the time of use. From the viewpoints of workability, handleability, etc., the structural polyurethane adhesive is preferably a two-component curing type adhesive.

[0017] The polyisocyanate component contains a first isocyanate component, a second isocyanate component, and a third isocyanate component. The first isocyanate component and the second isocyanate component contain a urethane prepolymer having two or more isocyanate groups at the molecular terminals (hereinafter referred to as an isocyanate group-terminated urethane prepolymer). The third isocyanate component contains a carbodiimide modified product described later.

[0018] More specifically, the first isocyanate component contains a first isocyanate group-terminated urethane prepolymer. The first isocyanate group-terminated urethane prepolymer is a reaction product of a first raw material polyisocyanate and a first raw material polyol. The first raw material polyisocyanate and the first raw material polyol react such that the isocyanate groups are in excess with respect to the hydroxyl groups.

[0019] The first raw material polyisocyanate consists of aromatic polyisocyanates. Examples of the aromatic polyisocyanates include aromatic polyisocyanate monomers and aromatic polyisocyanate derivatives.

[0020] Examples of the aromatic polyisocyanate monomers include aromatic diisocyanates. Examples of the aromatic diisocyanates include tolylene diisocyanate, phenylene diisocyanate, diphenyl diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate, toluidine diisocyanate, and diphenyl ether diisocyanate. These can be used alone or in combination of two or more.

[0021] Examples of the aromatic polyisocyanate derivatives include modified products obtained by modifying the above aromatic polyisocyanate monomers by known methods. More specifically, examples of the aromatic polyisocyanate derivatives include uretdione modified products, isocyanurate modified products, allophanate modified products, polyol modified products, biuret modified products, urea modified products, oxadiazinetrione modified products, and carbodiimide modified products. Also, polymethylene polyphenylene polyisocyanate is included as an aromatic polyisocyanate derivative. These can be used alone or in combination of two or more.

[0022] These aromatic polyisocyanates can be used alone or in combination of two or more. From the viewpoint of adhesion characteristics, the aromatic polyisocyanate is preferably an aromatic polyisocyanate monomer, more preferably an aromatic diisocyanate, and even more preferably diphenylmethane diisocyanate.

[0023] In other words, from the viewpoint of adhesion characteristics, the first raw material polyisocyanate preferably consists of the monomer of diphenylmethane diisocyanate.

[0024] The first raw material polyol contains a macro polyol as an essential component. The macro polyol is a relatively high molecular weight organic compound having two or more hydroxyl groups.

[0025] The number average molecular weight of the macro polyol (hereinafter referred to as the first macro polyol) in the first raw material polyol is 200 or more. Further, the number average molecular weight of the first macro polyol is usually 15000 or less. The number average molecular weight is the polystyrene equivalent molecular weight measured by gel permeation chromatography (the same shall apply hereinafter).

[0026] The macro polyol is not particularly limited, and examples thereof include polyether polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, epoxy polyol, vegetable oil polyol, polyolefin polyol, acrylic polyol, and vinyl monomer-modified polyol. The macro polyol can be used alone or in combination of two or more.

[0027] Preferred examples of the macro polyol in the first raw material polyol include polyether polyol, polyester polyol, and polycarbonate polyol, and more preferred is polyether polyol.

[0028] Examples of the polyether polyol include polyoxyalkylene (C2-3) polyol and polytetramethylene ether polyol, and preferably polyoxyalkylene (C2-3) polyol.

[0029] More specifically, examples of the polyoxyalkylene (C2-3) polyol include polyoxyethylene polyol, polyoxypropylene polyol, polyoxytriethylene polyol, and polyoxyethylene·polyoxypropylene polyol (random or block copolymer). The polyoxyalkylene (C2-3) polyol can be used alone or in combination of two or more.

[0030] As the polyoxyalkylene (C2-3) polyol, preferably, polyoxypropylene polyol is mentioned, and more preferably, polyoxypropylene glycol is mentioned.

[0031] The number average molecular weight of the first macro polyol is, for example, 200 or more, preferably 300 or more, and more preferably 400 or more. Also, the number average molecular weight of the first macro polyol is, for example, 15000 or less, preferably 13000 or less, more preferably 12000 or less, still more preferably 10000 or less, still more preferably 8000 or less, and particularly preferably 5000 or less.

[0032] The hydroxyl equivalent of the first macro polyol is, for example, 150 or more, preferably 200 or more. Also, the hydroxyl equivalent of the first macro polyol is, for example, 10000 or less, preferably 8000 or less. Note that the hydroxyl equivalent can be calculated from the hydroxyl value.

[0033] The average number of hydroxyl groups of the first macro polyol is, for example, 1.8 or more, preferably 2 or more. Also, the average number of hydroxyl groups of the first macro polyol is, for example, 6 or less, preferably 4 or less, and more preferably 3 or less.

[0034] Note that the hydroxyl value and the hydroxyl equivalent can be measured, for example, in accordance with Method A or Method B of JIS K 1557-1 (2007). Also, the average number of hydroxyl groups can be calculated from the hydroxyl value, the hydroxyl equivalent, and the molecular weight. Also, the hydroxyl value, the hydroxyl equivalent, and the average number of hydroxyl groups can be calculated from the charging ratio of the raw material components (the same applies hereinafter).

[0035] As the first raw material polyol, particularly preferably, the first macro polyol having an average number of hydroxyl groups of 2 and the first macro polyol having an average number of hydroxyl groups of 3 are used in combination.

[0036] When a first macropolyalcohol with an average hydroxyl number of 2 and a first macropolyalcohol with an average hydroxyl number of 3 are used in combination, for 100 parts by mass of their total amount, the first macropolyalcohol with an average hydroxyl number of 3 is, for example, in excess of 50 parts by mass, preferably 60 parts by mass or more. Also, the first macropolyalcohol with an average hydroxyl number of 3 is, for example, 90 parts by mass or less, preferably 80 parts by mass or less. Further, the first macropolyalcohol with an average hydroxyl number of 2 is, for example, 10 parts by mass or more, preferably 20 parts by mass or more. The first macropolyalcohol with an average hydroxyl number of 2 is, for example, less than 50 parts by mass, preferably 40 parts by mass or less.

[0037] In addition, the first raw material polyol can contain a low molecular weight polyol as an optional component. The low molecular weight polyol is a relatively low molecular weight organic compound having two or more hydroxyl groups.

[0038] The molecular weight of the low molecular weight polyol (hereinafter, the first low molecular weight polyol) in the first raw material polyol is less than 200, preferably 180 or less.

[0039] Examples of the first low molecular weight polyol include dihydric alcohols, trihydric alcohols, and tetrahydric or higher alcohols. Examples of the dihydric alcohol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and dipropylene glycol. Examples of the trihydric alcohol include glycerin and trimethylolpropane. Examples of the tetrahydric or higher alcohol include pentaerythritol and diglycerin. These can be used alone or in combination of two or more.

[0040] Note that the content ratio of the first low-molecular-weight polyol is appropriately selected within a range that does not impair the excellent effects of the present invention. More specifically, the content ratio of the first low-molecular-weight polyol is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 0 parts by mass, with respect to 100 parts by mass of the total amount of the first raw material polyol. That is, from the viewpoint of adhesion characteristics, the first raw material polyol preferably does not contain the first low-molecular-weight polyol and consists of the first macro polyol.

[0041] And the first isocyanate group-terminated urethane prepolymer is obtained by reacting the first raw material polyisocyanate and the first raw material polyol by a known method. More specifically, the first raw material polyisocyanate and the first raw material polyol are blended at a predetermined ratio and subjected to a urethanization reaction.

[0042] In the urethanization reaction, the equivalent ratio (NCO / OH) of the isocyanate group in the first raw material polyisocyanate to the hydroxyl group in the first raw material polyol exceeds, for example, 1, preferably 1.1 or more, more preferably 1.3 or more, still more preferably 1.5 or more, and particularly preferably 1.9 or more. Also, the equivalent ratio (NCO / OH) is, for example, 50 The following , preferably 15 or less, more preferably 10 or less, still more preferably 3 or less, and particularly preferably 2.5 or less.

[0043] In the urethanization reaction, known polymerization methods are adopted. Examples of the polymerization method include bulk polymerization and solution polymerization. In bulk polymerization, for example, the above components are blended and reacted under a nitrogen atmosphere. In solution polymerization, for example, the above components are added to a known organic solvent and reacted under a nitrogen atmosphere. The reaction temperature is, for example, 50°C or higher, and for example, 120°C or lower, preferably 100°C or lower. Also, the reaction time is, for example, 0.5 hours or longer, preferably 1 hour or longer, and for example, 24 hours or shorter, preferably 15 hours or shorter. In solution polymerization, the blending ratio of the organic solvent is appropriately set according to the purpose and application. In the urethanization reaction, preferably, bulk polymerization (solvent-free reaction) is adopted.

[0044] In addition, in the above urethanization reaction, a known urethanization catalyst is added as necessary. Also, unreacted polyisocyanate is removed by a known method as necessary. Thereby, a first isocyanate component containing a first isocyanate group-terminated urethane prepolymer is obtained.

[0045] Examples of the first isocyanate group-terminated urethane prepolymer preferably include a first isocyanate group-terminated urethane prepolymer that is a reaction product of an aromatic polyisocyanate and a polyether polyol, and more preferably, a first isocyanate group-terminated urethane prepolymer that is a reaction product of diphenylmethane diisocyanate and a polyether polyol.

[0046] In addition, the first isocyanate component can contain, if necessary, free (unreacted) first raw material polyisocyanate, organic solvent, and urethanization catalyst. Also, the free (unreacted) first raw material polyisocyanate, organic solvent, and urethanization catalyst may be removed by known removal means. Examples of the removal means include extraction and distillation.

[0047] The content ratio of the free (unreacted) first raw material polyisocyanate is, from the viewpoint of adhesion properties, for example, 8.0% by mass or less, preferably 5.0% by mass or less, based on the total amount of the polyisocyanate component. Further, the content ratio of the first isocyanate group-terminated urethane prepolymer is, for example, 92.0% by mass or more, preferably 95.0% by mass or more, based on the total amount of the first isocyanate component, and is usually 100% by mass or less.

[0048] The average number of isocyanate groups of the first isocyanate component (solid content) is, for example, 1.2 or more, preferably 1.5 or more, more preferably 2 or more. Further, the average number of isocyanate groups of the first isocyanate component (solid content) is, for example, 4 or less, preferably 3 or less.

[0049] The isocyanate group equivalent of the first isocyanate component (solid content) is, for example, 84 or more, preferably 150 or more, more preferably 168 or more. Further, the isocyanate group equivalent of the first isocyanate component (solid content) is, for example, 3500 or less, preferably 2800 or less, more preferably 2335 or less. The isocyanate group equivalent is synonymous with the amine equivalent and can be determined by the method A or B of JIS K 1603-1 (2007).

[0050] The content of the isocyanate group of the first isocyanate component (solid content) (isocyanate group content, NCO%) is, for example, 1.2% by mass or more, preferably 1.5% by mass or more, more preferably 1.8% by mass or more, further preferably 2.0% by mass or more, particularly preferably 2.1% by mass or more. Further, the content of the isocyanate group of the first isocyanate component (solid content) is, for example, 50% by mass or less, preferably 28% by mass or less, more preferably 25% by mass or less, further preferably 10% by mass or less, particularly preferably 6% by mass or less.

[0051] The viscosity of the solid content of the first isocyanate component at 25°C is, for example, 1000 mPa·s or more, preferably 5000 mPa·s or more. Also, the viscosity of the solid content of the first isocyanate component at 25°C is, for example, 200,000 mPa·s or less, preferably 100,000 mPa·s or less. The viscosity is measured using a B-type viscometer (the same applies hereinafter).

[0052] The second isocyanate component contains a second isocyanate group-terminated urethane prepolymer. The second isocyanate group-terminated urethane prepolymer is a reaction product of a second raw material polyisocyanate and a second raw material polyol. The second raw material polyisocyanate and the second raw material polyol react such that the isocyanate group is in excess with respect to the hydroxyl group.

[0053] The second raw material polyisocyanate consists of an aromatic aliphatic polyisocyanate and / or an aliphatic polyisocyanate.

[0054] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic polyisocyanate monomers. Examples of the aromatic aliphatic polyisocyanate monomers include aromatic aliphatic diisocyanates. Examples of the aromatic aliphatic diisocyanates include xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate, and ω,ω'-diisocyanate-1,4-diethylbenzene. Examples of xylylene diisocyanate include 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate. These can be used alone or in combination of two or more. Preferably, aromatic aliphatic diisocyanates are included, more preferably xylylene diisocyanate is included, and even more preferably 1,3-xylylene diisocyanate is included.

[0055] Examples of the aliphatic polyisocyanate include chain aliphatic polyisocyanates and alicyclic polyisocyanates.

[0056] Examples of the chain aliphatic polyisocyanate include chain aliphatic polyisocyanate monomers. Examples of the chain aliphatic polyisocyanate monomers include chain aliphatic diisocyanates. Examples of the chain aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 1,2 - propane diisocyanate, 1,2 - butane diisocyanate, 2,3 - butane diisocyanate, 1,3 - butane diisocyanate, 2,4,4 - trimethylhexamethylene diisocyanate, 2,2,4 - trimethylhexamethylene diisocyanate, and 2,6 - diisocyanatomethyl caproate. These can be used alone or in combination of two or more. Preferably, chain aliphatic diisocyanates are included, and more preferably, pentamethylene diisocyanate and hexamethylene diisocyanate are included.

[0057] Examples of the alicyclic polyisocyanate include alicyclic polyisocyanate monomers. Examples of the alicyclic polyisocyanate monomers include alicyclic diisocyanates. Examples of the alicyclic diisocyanates include isophorone diisocyanate (IPDI), norbornene diisocyanate (NBDI), methylene bis(cyclohexyl isocyanate) (H 12 MDI), and bis(isocyanatomethyl)cyclohexane (H6XDI). These can be used alone or in combination of two or more. Preferably, alicyclic diisocyanates are included, and more preferably, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate), and bis(isocyanatomethyl)cyclohexane are included.

[0058] Examples of the aromatic aliphatic polyisocyanate and / or aliphatic polyisocyanate include derivatives of the above-mentioned monomers. Examples of the derivatives include derivatives of aromatic aliphatic polyisocyanate monomers, derivatives of chain aliphatic polyisocyanate monomers, and derivatives of alicyclic polyisocyanate monomers. Further examples of the derivatives include modified products obtained by modifying the above monomers by known methods. More specific examples of the derivatives include uretdione-modified products, isocyanurate-modified products, allophanate-modified products, polyol-modified products, biuret-modified products, urea-modified products, oxadiazinetrione-modified products, and carbodiimide-modified products. These can be used alone or in combination of two or more.

[0059] These aromatic aliphatic polyisocyanates and / or aliphatic polyisocyanates can be used alone or in combination of two or more. From the viewpoint of adhesion properties, the aromatic aliphatic polyisocyanate and / or aliphatic polyisocyanate preferably includes aromatic aliphatic polyisocyanate monomers, chain aliphatic polyisocyanate monomers, and alicyclic polyisocyanate monomers, more preferably includes aromatic aliphatic diisocyanates, chain aliphatic diisocyanates, and alicyclic diisocyanates, and still more preferably includes xylylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate), and bis(isocyanatomethyl)cyclohexane.

[0060] In other words, from the viewpoint of adhesion properties, the second raw material polyisocyanate preferably contains at least one selected from the group consisting of xylylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate), and bis(isocyanatomethyl)cyclohexane.

[0061] As the aromatic aliphatic polyisocyanate and / or aliphatic polyisocyanate, from the viewpoint of adhesion properties, particularly preferably, xylylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate and bis(isocyanatomethyl)cyclohexane can be mentioned. In other words, the second raw material polyisocyanate contains at least one selected from the group consisting of xylylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate and bis(isocyanatomethyl)cyclohexane, particularly preferably from the viewpoint of adhesion properties.

[0062] As the aromatic aliphatic polyisocyanate and / or aliphatic polyisocyanate, from the viewpoint of adhesion properties, particularly preferably, xylylene diisocyanate can be mentioned. In other words, the second raw material polyisocyanate contains xylylene diisocyanate, particularly preferably from the viewpoint of adhesion properties.

[0063] The second raw material polyol contains a polyether polyol as an essential component. In the second raw material polyol, the polyether polyol may be a relatively low molecular weight (molecular weight less than 300) polyether polyol. Also, the polyether polyol may be a relatively high molecular weight (molecular weight 300 or more) polyether polyol.

[0064] In the second raw material polyol, examples of the polyether polyol include the same polyether polyols as the polyether polyols described above as the first macro polyol (however, excluding the molecular weight).

[0065] Examples of the polyether polyol preferably include polyoxyalkylene (C2-3) polyol, more preferably polyoxypropylene polyol, and even more preferably polyoxypropylene glycol.

[0066] In the second raw material polyol, from the viewpoint of adhesion properties, the number average molecular weight of the polyether polyol is 160 or more, preferably 240 or more, more preferably 300 or more, still more preferably 400 or more. Also, from the viewpoint of adhesion properties, the number average molecular weight of the polyether polyol is 4900 or less, preferably 4800 or less, more preferably 4500 or less, still more preferably 4000 or less, still more preferably 3000 or less, still more preferably 2000 or less, still more preferably 1500 or less, still more preferably 800 or less, and particularly preferably 500 or less.

[0067] In the second raw material polyol, from the viewpoint of adhesion strength, the average number of hydroxyl groups of the polyether polyol is, for example, 1.8 or more, preferably 2 or more. Also, from the viewpoint of adhesion strength, the average number of hydroxyl groups of the polyether polyol is, for example, 6 or less, preferably 4 or less, more preferably 3 or less, and particularly preferably 2.5 or less.

[0068] In other words, the second raw material polyol preferably contains a polyether polyol having an average number of hydroxyl groups of 2 or more and 4 or less, and more preferably contains a polyether polyol having an average number of hydroxyl groups of 2 or more and 3 or less.

[0069] Also, the second raw material polyol can contain other polyols as optional components. The other polyols are polyols excluding the above polyether polyols. Examples of the other polyols include other macro polyols (hereinafter, the second macro polyol) and other low molecular weight polyols (hereinafter, the second low molecular weight polyol).

[0070] The other macro polyol (the second macro polyol) is a macro polyol excluding the above polyether polyol. The other macro polyols are not particularly limited, and known macro polyols can be mentioned. The other macro polyols can be used alone or in combination of two or more.

[0071] The number average molecular weight of the other macro polyol (the second macro polyol) is, for example, 300 or more, preferably 400 or more, more preferably 500 or more. Also, the number average molecular weight of the other macro polyol (the second macro polyol) is, for example, 15000 or less, preferably 13000 or less, more preferably 12000 or less, still more preferably 10000 or less, still more preferably 8000 or less, and particularly preferably 5000 or less.

[0072] Examples of the other low molecular weight polyol (the second low molecular weight polyol) include the low molecular weight polyols described above as the first raw material polyol. The other low molecular weight polyols can be used alone or in combination of two or more.

[0073] The molecular weight of the other low molecular weight polyol (the second low molecular weight polyol) is less than 300, preferably 250 or less.

[0074] In the second raw material polyol, the content ratio of the polyols excluding the polyether polyol (the second macro polyol and the second low molecular weight polyol) is appropriately selected within a range that does not impair the excellent effects of the present invention.

[0075] More specifically, the content ratio of the other macro polyol (the second macro polyol) is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 0 parts by mass, based on 100 parts by mass of the total amount of the second raw material polyol.

[0076] Also, the content ratio of the other low molecular weight polyol (the second low molecular weight polyol) is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 0 parts by mass, based on 100 parts by mass of the total amount of the second raw material polyol.

[0077] That is, from the viewpoint of adhesive strength, the second raw material polyol preferably does not contain polyols other than polyether polyols (the second macro polyol and the second low molecular weight polyol), and consists of polyether polyols.

[0078] And the second isocyanate group-terminated urethane prepolymer is obtained by reacting the second raw material polyisocyanate and the second raw material polyol by a known method. More specifically, the second raw material polyisocyanate and the second raw material polyol are blended at a predetermined ratio and subjected to a urethanization reaction.

[0079] In the urethanization reaction, the equivalent ratio (NCO / OH) of the isocyanate group in the second raw material polyisocyanate to the hydroxyl group in the second raw material polyol exceeds, for example, 1, preferably 1.1 or more, more preferably 1.3 or more, still more preferably 1.5 or more, and particularly preferably 1.9 or more. Also, the equivalent ratio (NCO / OH) is, for example, 50 The following , preferably 30 or less, more preferably 20 or less, still more preferably 10 or less, and particularly preferably 8 or less.

[0080] In the urethanization reaction, a known polymerization method is adopted. Examples of the polymerization method include bulk polymerization and solution polymerization. In bulk polymerization, for example, the above components are blended and reacted under a nitrogen atmosphere. In solution polymerization, for example, the above components are added to a known organic solvent under a nitrogen atmosphere and reacted. The reaction temperature is, for example, 50°C or higher, and for example, 120°C or lower, preferably 100°C or lower. Also, the reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, and for example, 24 hours or less, preferably 15 hours or less. In solution polymerization, the blending ratio of the organic solvent is appropriately set according to the purpose and application. In the urethanization reaction, preferably, bulk polymerization (solvent-free reaction) is adopted.

[0081] In the urethanization reaction, a known urethanization catalyst is added as necessary. Further, unreacted polyisocyanate is removed by a known method as necessary. Thereby, a second isocyanate component containing a second isocyanate group-terminated urethane prepolymer is obtained.

[0082] As the second isocyanate group-terminated urethane prepolymer, preferably, a second isocyanate group-terminated urethane prepolymer which is a reaction product of an aromatic aliphatic polyisocyanate and a polyether polyol is mentioned, and more preferably, a second isocyanate group-terminated urethane prepolymer which is a reaction product of xylylene diisocyanate and a polyether polyol is mentioned.

[0083] Further, the second isocyanate component can contain a free (unreacted) second raw material polyisocyanate, an organic solvent, and a urethanization catalyst as necessary. Further, the free (unreacted) second raw material polyisocyanate, the organic solvent, and the urethanization catalyst may be removed by known removal means. Examples of the removal means include extraction and distillation. Preferably, the second isocyanate component is distilled, and from the viewpoint of improving the adhesive strength, the second isocyanate component is more preferably thin-film distilled.

[0084] The content ratio of the free (unreacted) second raw material polyisocyanate is, for example, 5.0% by mass or less, preferably 1.0% by mass or less, based on the total amount of the second isocyanate component, from the viewpoint of the adhesive strength. Further, the content ratio of the second isocyanate group-terminated urethane prepolymer is, for example, 95.0% by mass or more, preferably 99.0% by mass or more, and usually 100% by mass or less, based on the total amount of the second isocyanate component.

[0085] The average number of isocyanate groups of the second isocyanate component (solid content) is, for example, 1.2 or more, preferably 1.5 or more, more preferably 2 or more. Further, the average number of isocyanate groups of the second isocyanate component (solid content) is, for example, 4 or less, preferably 3 or less.

[0086] The isocyanate group equivalent weight of the second isocyanate component (solid content) is, for example, 84 or more, preferably 150 or more, more preferably 168 or more. Also, the isocyanate group equivalent weight of the second isocyanate component (solid content) is, for example, 3500 or less, preferably 2800 or less, more preferably 2335 or less.

[0087] The content of isocyanate groups in the second isocyanate component (solid content) (isocyanate group content, NCO%) is, for example, 1.2% by mass or more, preferably 1.5% by mass or more, more preferably 1.8% by mass or more, still more preferably 2.0% by mass or more. Also, the content of isocyanate groups in the second isocyanate component (solid content) is, for example, 50% by mass or less, preferably 28% by mass or less, more preferably 25% by mass or less, still more preferably 12% by mass or less.

[0088] The viscosity of the solid content of the second isocyanate component at 25°C is, for example, 1000 mPa·s or more, preferably 5000 mPa·s or more. Also, the viscosity of the solid content of the second isocyanate component at 25°C is, for example, 200,000 mPa·s or less, preferably 100,000 mPa·s or less, more preferably 50,000 mPa·s or less, particularly preferably 10,000 mPa·s or less.

[0089] Also, the viscosity of the solid content of the second isocyanate component at 30°C is, for example, 100 mPa·s or more, preferably 1000 mPa·s or more. Also, the viscosity of the solid content of the second isocyanate component at 30°C is, for example, 500,000 mPa·s or less, preferably 200,000 mPa·s or less, more preferably 100,000 mPa·s or less, still more preferably 50,000 mPa·s or less, particularly preferably 10,000 mPa·s or less.

[0090] The third polyisocyanate component contains a carbodiimide-modified product of an aromatic polyisocyanate, and preferably consists of a carbodiimide-modified product of an aromatic polyisocyanate.

[0091] The carbodiimide-modified product of an aromatic polyisocyanate is a reaction product obtained by the carbodiimidization reaction of an aromatic polyisocyanate.

[0092] Examples of the aromatic polyisocyanate include the aromatic polyisocyanates described above as the first raw material polyisocyanate, and more specifically, aromatic polyisocyanate monomers and their derivatives. From the viewpoint of adhesion properties, as the aromatic polyisocyanate, preferably, aromatic polyisocyanate monomers are included, more preferably, aromatic diisocyanates are included, and even more preferably, diphenylmethane diisocyanate is included.

[0093] Examples of the carbodiimidization reaction include a decarboxylation condensation reaction. In the decarboxylation condensation reaction, for example, an aromatic polyisocyanate is heated in the presence of a carbodiimidization catalyst.

[0094] The carbodiimidization catalyst is not particularly limited, and examples thereof include trialkyl phosphate ester compounds, phospholene oxide compounds, phospholene sulfide compounds, phosphine oxide compounds, and phosphine compounds. The blending ratio of the carbodiimidization catalyst is set as appropriate. Also, the reaction conditions in the carbodiimidization reaction are set as appropriate according to the type of the aromatic polyisocyanate and the type of the catalyst. Further, if necessary, the aromatic polyisocyanate may be subjected to a carbodiimidization reaction in the presence of the above-described organic solvent.

[0095] By the carbodiimidization reaction, the aromatic polyisocyanate undergoes decarboxylation condensation to generate a carbodiimide group. As a result, a carbodiimide-modified product of the aromatic polyisocyanate is obtained.

[0096] Further, the third isocyanate component can contain, if necessary, a free (unreacted) aromatic polyisocyanate, an organic solvent, and a carbodiimidization catalyst. Further, the free (unreacted) aromatic polyisocyanate, the organic solvent, and the carbodiimidization catalyst may be removed by known removal means. Examples of the removal means include extraction and distillation.

[0097] Also, as the third isocyanate component, a commercially available carbodiimide-modified product of an aromatic polyisocyanate may be used. Examples of the commercially available product include Coronate MX (carbodiimide-modified product of diphenylmethane diisocyanate, NCO content 29.0% by mass, manufactured by Tosoh Corporation).

[0098] And the polyisocyanate component is prepared by mixing the first isocyanate component, the second isocyanate component, and the third isocyanate component.

[0099] With respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component, the proportion of the first isocyanate component is, for example, 8% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more. Also, the proportion of the first isocyanate component is, for example, 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less. When the proportion of the first isocyanate component is within the above range, particularly excellent adhesion characteristics can be obtained.

[0100] With respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component, the proportion of the second isocyanate component is 2% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, particularly preferably 25% by mass or more, from the viewpoint of adhesion properties. Also, the proportion of the second isocyanate component is 35% by mass or less, preferably 33% by mass or less, more preferably 31% by mass or less, still more preferably 30% by mass or less. When the proportion of the second isocyanate component is within the above range, particularly excellent adhesion properties can be obtained.

[0101] With respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component, the proportion of the third isocyanate component is, for example, 8% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more. Also, the proportion of the third isocyanate component is, for example, 90% by mass or less, preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 40% by mass or less. When the proportion of the third isocyanate component is within the above range, particularly excellent adhesion properties can be obtained.

[0102] Note that the method of mixing the first isocyanate component, the second isocyanate component, and the third isocyanate component is not particularly limited, and known methods are adopted. Thereby, a polyisocyanate component is obtained.

[0103] And the viscosity of the solid content of the polyisocyanate component at 25°C is, for example, 1000 mPa·s or more, preferably 5000 mPa·s or more, and is, for example, 200,000 mPa·s or less, preferably 100,000 mPa·s or less.

[0104] The polyol component contains, for example, a macro polyol (hereinafter referred to as the third macro polyol).

[0105] Examples of the third macro polyol include polyether polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, epoxy polyol, vegetable oil polyol, polyolefin polyol, acrylic polyol, and vinyl monomer-modified polyol. These third macro polyols can be used alone or in combination of two or more. Preferably, the third macro polyol is a polyether polyol.

[0106] Examples of the polyether polyol include the above-mentioned polyether polyols. More specifically, examples of the polyether polyol include, for example, polyoxyalkylene (C2-3) polyol and polytetramethylene ether polyol, and preferably, polyoxyalkylene (C2-3) polyol.

[0107] More specifically, examples of the polyoxyalkylene (C2-3) polyol include, for example, polyoxyethylene polyol, polyoxypropylene polyol, polyoxytriethylene polyol, and polyoxyethylene·polyoxypropylene polyol (random or block copolymer). The polyoxyalkylene (C2-3) polyol can be used alone or in combination of two or more.

[0108] Preferably, the macro polyol (third macro polyol) in the polyol component is a polyoxyethylene·polyoxypropylene polyol (block copolymer).

[0109] From the viewpoint of adhesive strength, the number average molecular weight of the third macro polyol in the polyol component is, for example, 500 or more, preferably 1000 or more, more preferably 1500 or more. Also, from the viewpoint of adhesive strength, the number average molecular weight of the third macro polyol is, for example, 10000 or less, more preferably 7500 or less, more preferably 5000 or less.

[0110] In the polyol component, the hydroxyl equivalent of the third macro-polyol is, for example, 150 or more, preferably 200 or more. Also, the hydroxyl equivalent of the third macro-polyol is, for example, 10000 or less, preferably 8000 or less.

[0111] In the polyol component, from the viewpoint of adhesion strength, the average number of hydroxyl groups of the third macro-polyol is, for example, 1.9 or more, preferably 2.0 or more, more preferably 2.3 or more. Also, from the viewpoint of adhesion strength, the average number of hydroxyl groups of the third macro-polyol is, for example, 4.0 or less, preferably 3.5 or less, more preferably 3.0 or less.

[0112] Also, the polyol component can contain, if necessary, a low molecular weight polyol (hereinafter referred to as the third low molecular weight polyol). The molecular weight of the third low molecular weight polyol is less than 200, preferably 180 or less. Examples of the third low molecular weight polyol include the above-described first low molecular weight polyol. The third low molecular weight polyol can be used alone or in combination of two or more.

[0113] The polyol component preferably contains the third low molecular weight polyol. That is, the polyol component preferably consists of the third macro-polyol and the third low molecular weight polyol.

[0114] The content ratio of the third low molecular weight polyol to the polyol component is appropriately selected within a range that does not impair the excellent effects of the present invention. More specifically, the content ratio of the third low molecular weight polyol is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of the total amount of the polyol component. Also, the content ratio of the third low molecular weight polyol is, for example, 0 parts by mass or more, preferably 1 part by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the total amount of the polyol component.

[0115] In addition, the structural polyurethane adhesive can contain additives as required. Examples of the additives include plasticizers, fillers, compatibilizers, urethanization catalysts, anti-aging agents, antioxidants, ultraviolet absorbers, heat stabilizers, polymer light stabilizers, organic solvents, pigments, dyes, defoamers, dispersants, leveling agents, thixotropic agents, anti-blocking agents, release agents, lubricants, interlayer regulators, and viscosity regulators. The content ratio of the additives is not particularly limited and is appropriately set according to the purpose and application.

[0116] Note that the additives may be added, for example, to a mixture of a polyisocyanate component and a polyol component (such as a one-component curing adhesive, etc.). Also, the additives may be contained, for example, in the main agent described later, may be contained in the curing agent described later, or may be contained in both of them.

[0117] On the other hand, from the viewpoint of workability, the structural polyurethane adhesive preferably does not contain an organic solvent. That is, the structural polyurethane adhesive is preferably a solvent-free adhesive.

[0118] In the solvent-free adhesive, the polyisocyanate component is prepared, for example, without using an organic solvent or is desolvated by a known method after being prepared using an organic solvent.

[0119] Also, in the solvent-free adhesive, the polyol component is prepared, for example, without using an organic solvent or is desolvated by a known method after being prepared using an organic solvent.

[0120] In addition, the structural polyurethane adhesive is preferably a two-component curable adhesive comprising a main agent containing a polyisocyanate component and a curing agent containing a polyol component. The two-component curable adhesive is a resin composition kit (two-component kit) for forming a cured product by blending (mixing) the separately prepared main agent and curing agent at the time of use. That is, by mixing the main agent and the curing agent, a resin mixture (polyurethane mixture) is obtained, and by subjecting the resin mixture to a curing reaction, a cured product (polyurethane cured product) is obtained.

[0121] And in the above structural polyurethane adhesive, the polyisocyanate component contains a first isocyanate component, a second isocyanate component, and a third isocyanate component. The first isocyanate component includes a first isocyanate group-terminated urethane prepolymer that is a reaction product of a first raw material polyisocyanate composed of an aromatic polyisocyanate and a first raw material polyol containing a macropolyol. The second isocyanate component includes a second isocyanate group-terminated urethane prepolymer that is a reaction product of a second raw material polyisocyanate composed of an araliphatic polyisocyanate and / or an aliphatic polyisocyanate and a second raw material polyol containing a polyether polyol having a number average molecular weight of 160 or more and 4900 or less. Further, the third isocyanate component contains a carbodiimide-modified product of an aromatic polyisocyanate. And the ratio of the second isocyanate component is within a predetermined range with respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component. Therefore, the above structural polyurethane adhesive has excellent adhesion properties.

[0122] Therefore, the above structural polyurethane adhesive is suitably used for adhering each member in a structure composed of a plurality of members or the like. Examples of the structure include buildings, automobiles, transportation equipment, and ships.

[0123] In the use of a structural polyurethane adhesive, for example, a mixture containing a polyisocyanate component and a polyol component is applied to a member by a known method, cured, and, if necessary, allowed to cure.

[0124] From the viewpoint of workability, the viscosity of the mixture containing the polyisocyanate component and the polyol component at 25°C is, for example, 100 mPa·s or more, preferably 300 mPa·s or more. Also, the viscosity of the mixture at 25°C is, for example, 500000 mPa·s or less, preferably 100000 mPa·s or less, more preferably 50000 mPa·s or less.

[0125] Also, the curing conditions and the curing conditions are appropriately set. More specifically, the curing temperature is, for example, 10°C or more, preferably 20°C or more. Also, the curing temperature is, for example, 200°C or less, preferably 150°C or less. Also, the curing time is, for example, 5 minutes or more, preferably 10 minutes or more. Also, the curing time is, for example, 10 hours or less, preferably 5 hours or less. Also, the curing temperature is, for example, 10°C or more, preferably 20°C or more. Also, the curing temperature is, for example, 80°C or less, preferably 70°C or less. Also, the curing time is, for example, 1 hour or more, preferably 2 hours or more. Also, the curing time is, for example, 2 weeks or less, preferably 1 week or less.

[0126] Thereby, the structural polyurethane adhesive can be cured and each member can be well adhered.

Example

[0127] Next, the present invention will be described based on Examples and Comparative Examples, but the present invention is not limited by the following Examples. Note that "parts" and "%" are based on mass unless otherwise specified. Also, specific numerical values such as the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values (numerical values defined as "hereinafter", "less than") or lower limit values (numerical values defined as "above", "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above "Mode for Carrying Out the Invention".

[0128] <Monomer concentration> After preparing the first isocyanate component and the second isocyanate component, the concentration of the monomer (the first raw material polyisocyanate or the second raw material polyisocyanate) remaining was measured as follows.

[0129] (1) Standard solution for the first isocyanate component Cosmonate PH(B) (trade name, MDI, manufactured by Mitsui Chemicals SKC Polyurethane) was reacted with a large excess of methanol, and the resulting crystals were recrystallized with methanol and purified. Next, the obtained crystals were analyzed by NMR and LC to confirm that they did not contain a solvent and 2,4'-isomer (area ratio 1% or less). The obtained crystals were referred to as "PH(B) methyl urethanated standard". Next, 10 mg of the PH(B) methyl urethanated standard was precisely weighed into a 50 mL volumetric flask, the mass was recorded, and it was diluted with dichloroethane (DCE) to a total volume of 50 mL. Then, 2 mL (solution A) and 10 mL (solution B) of the above solution were taken into a 50 mL volumetric flask and diluted with dichloroethane (DCE) to a total volume of 50 mL, respectively. The diluted solution of solution A was used as a standard solution corresponding to a quantitative value of 0.4%. Also, the diluted solution of solution B was used as a standard solution corresponding to a quantitative value of 2.0%. These standard solutions were measured by HPLC under the following conditions. Then, a calibration curve was created from the area values of the obtained chromatograms.

[0130] (2) Standard solution for the second isocyanate component Weighed 1.97 g of dibenzylamine into a 50 mL volumetric flask and diluted it with dichloroethane (DCE). The resulting diluted solution was referred to as the "labeling reagent". Next, weighed 25 mg of Takenate 500 (trade name, XDI, manufactured by Mitsui Chemicals) into a 50 mL volumetric flask, recorded the mass, added 10 mL of the labeling reagent, left it standing for 10 minutes, and then diluted it with dichloroethane to a total volume of 50 mL. Next, took 1 mL (Solution C) and 2 mL (Solution D) of the above solution into a 50 mL volumetric flask and diluted each with dichloroethane (DCE) to a total volume of 50 mL. The diluted solution of Solution C was used as a standard solution corresponding to a quantitative value of 0.5%. Also, the diluted solution of Solution D was used as a standard solution corresponding to a quantitative value of 1.0%. These standard solutions were measured by HPLC under the following conditions. And a calibration curve was created from the area values of the obtained chromatograms.

[0131] (3) Actual measurement From the first isocyanate component and the second isocyanate component, measurement samples were prepared as follows and measured by HPLC.

[0132] <First isocyanate component> Prepared a methyl urethanation reagent (methanol / 1,2-dichloroethane = 1 / 1 (vol / vol) mixture) in advance. Also, weighed 0.1 g of the first isocyanate component into a 50 mL volumetric flask and recorded the mass. Then, put 10 mL of the methyl urethanation reagent into the volumetric flask and dissolved the first isocyanate component. After that, covered the volumetric flask and left it standing overnight, and used the diluted solution to a total volume of 50 mL with dichloroethane as the measurement sample.

[0133] <Second isocyanate component> Weighed 0.1 g of the second isocyanate component into a 50 mL volumetric flask and recorded the mass. Added 10 mL of the labeling reagent to the volumetric flask and left it standing for 10 minutes. Then, used the diluted solution to a total volume of 50 mL with dichloroethane (DCE) as the measurement sample.

[0134] <hplc> The measurement sample was subjected to HPLC measurement under the following conditions, and the concentration of the unreacted first raw material polyisocyanate or the second raw material polyisocyanate was calculated based on the calibration curve. In addition, the concentration of the unreacted second raw material polyisocyanate when PDI, HDI, and H6XDI were used was also measured by the same method as described above.

[0135] · HPLC conditions Apparatus; Prominence (manufactured by Shimadzu Corporation) Pump; LC-20AT Degasser; DGU-20A3 Autosampler; SIL-20A Column oven; COT-20A Detector: SPD-20A Column; SHISEIDO SILICA SG-120 Column temperature; 40 °C Eluent ; First isocyanate component and standard solution for first isocyanate component n-hexane / methanol / 1,2-dichloroethane = 84 / 8 / 8 (volume ratio) ; Second isocyanate component and standard solution for second isocyanate component n-hexane / methanol / 1,2-dichloroethane = 90 / 5 / 5 (volume ratio) Flow rate; 0.2 mL / min Detection method ; First isocyanate component and standard solution for first isocyanate component UV235 nm ; Second isocyanate component and standard solution for second isocyanate component UV225 nm

[0136] 1. Polyisocyanate component (Preparation Example 1) First isocyanate component (MDI prepolymer) 289 parts by mass of Actocol DL4000 (trade name, a polyether polyol with a number average molecular weight of 4000 and an average number of hydroxyl groups of 2, manufactured by Mitsui Chemicals), 578 parts by mass of Actocol T-5000 (trade name, a polyether polyol with a number average molecular weight of 5000 and an average number of hydroxyl groups of 3, manufactured by Mitsui Chemicals), and 133 parts by mass of 4,4'-diphenylmethane diisocyanate (MDI) as the first raw material polyisocyanate were mixed. The equivalent ratio (NCO / OH) at this time was 2.16. Next, the obtained mixture was stirred at 60°C for 1 hour in a nitrogen stream, and further stirred at 70°C for 4 hours to cause a urethanization reaction. Thereby, a first isocyanate component containing a first isocyanate group-terminated urethane prepolymer (MDI prepolymer) was obtained. The solid content concentration of the MDI prepolymer was 100%, and the isocyanate group content was 2.3% by mass.

[0137] (Preparation Example 2) Third Isocyanate Component (MDI Carbodiimide) As the third isocyanate component, Coronate MX (a carbodiimide-modified product of diphenylmethane diisocyanate, NCO content 29.0% by mass, manufactured by Tosoh Corporation) was prepared. Hereinafter, the solid content in Coronate MX is referred to as MDI carbodiimide.

[0138] (Preparation Example 3) Second Isocyanate Component (XDI / D-400) 264.0 parts by mass of Actocol D-400 (trade name, a polyether polyol with a number average molecular weight of 400 and an average number of hydroxyl groups of 2, manufactured by Mitsui Chemicals) as the second raw material polyol and 736.0 parts by mass of 1,3-xylylene diisocyanate (XDI) as the second raw material polyisocyanate were mixed. The equivalent ratio (NCO / OH) at this time was 6. Next, the obtained mixture was stirred at 70°C for 6 to 24 hours in a nitrogen stream to cause a urethanization reaction.

[0139] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155°C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10°C). As a result, a second isocyanate component (XDI / D-400) containing a urethane prepolymer having a second isocyanate group at the terminal was obtained.

[0140] The solid content concentration of the second isocyanate component (XDI / D-400) was 100%, the isocyanate group content was 10.5% by mass, and the viscosity at 25°C was 9300 mPa·s. Also, the content ratio of the second raw material polyisocyanate (XDI monomer) to the total amount of the second isocyanate component was 0.20% by mass.

[0141] The viscosity was determined in accordance with JIS K 7117-1 (1999) using a B-type viscometer (model number TVB-10M, rotor No. 4, rotation speed 12 rpm) , measurement (the same shall apply hereinafter).

[0142] (Preparation Example 4) Second isocyanate component (HDI / D-400) As the second raw material polyisocyanate, hexamethylene diisocyanate (HDI) was used, and as the second raw material polyol, Actocol D-400 (trade name, polyether polyol having a number average molecular weight of 400 and an average number of hydroxyl groups of 2, manufactured by Mitsui Chemicals, Inc.) was used, and the equivalent ratio (NCO / OH) was set to 6. These were stirred in a nitrogen stream at 110°C for 6 to 24 hours to cause a urethanization reaction.

[0143] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155°C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10°C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (HDI / D-400) containing a urethane prepolymer having a second isocyanate group at the terminal was obtained.

[0144] The solid content concentration of the second isocyanate component (HDI / D-400) was 100%, the isocyanate group content was 10.2% by mass, and the viscosity at 25°C was 1400 mPa·s. Also, the content ratio of the second raw material polyisocyanate (HDI monomer) to the total amount of the second isocyanate component was 0.23% by mass.

[0145] (Preparation Example 5) Second Isocyanate Component (PDI / D-400) As the second raw material polyisocyanate, pentamethylene diisocyanate (PDI) was used, and as the second raw material polyol, Actocol D-400 (trade name, polyether polyol with a number average molecular weight of 400 and an average number of hydroxyl groups of 2, manufactured by Mitsui Chemicals) was used, and the equivalent ratio (NCO / OH) was set to 6. These were stirred in a nitrogen stream at 110°C for 6 to 24 hours to cause a urethanization reaction.

[0146] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155°C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10°C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (PDI / D-400) containing a second isocyanate group-terminated urethane prepolymer was obtained.

[0147] The solid content concentration of the second isocyanate component (PDI / D-400) was 100%, the isocyanate group content was 10.9% by mass, and the viscosity at 25°C was 1700 mPa·s. Also, the content ratio of the second raw material polyisocyanate (PDI monomer) to the total amount of the second isocyanate component was 0.20% by mass.

[0148] (Preparation Example 6) Second Isocyanate Component (H6XDI / D-400) As the second raw material polyisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI) was used, and as the second raw material polyol, Actocol D-400 (trade name, polyether polyol with a number average molecular weight of 400 and an average number of hydroxyl groups of 2, manufactured by Mitsui Chemicals) was used, and the equivalent ratio (NCO / OH) was set to 6. These were stirred in a nitrogen stream at 70°C for 6 to 24 hours to cause a urethanization reaction.

[0149] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155°C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10°C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (H6XDI / D-400) containing a second isocyanate group-terminated urethane prepolymer was obtained.

[0150] The solid content concentration of the second isocyanate component (H6XDI / D-400) was 100%, the isocyanate group content was 11.4% by mass, and the viscosity at 25°C was 14,000 mPa·s. Also, the content ratio of the second raw material polyisocyanate (H6XDI monomer) to the total amount of the second isocyanate component was 0.80% by mass.

[0151] (Preparation Example 7) Second isocyanate component (XDI / T-700) As the second raw material polyisocyanate, 1,3-xylylene diisocyanate (XDI) was used, and as the second raw material polyol, Actocol T-700 (trade name, polyether polyol having a number average molecular weight of 700 and an average number of hydroxyl groups of 3, manufactured by Mitsui Chemicals, Inc.) was used, and the equivalent ratio (NCO / OH) was set to 10. These were stirred at 70°C for 6 to 24 hours in a nitrogen stream to cause a urethanization reaction.

[0152] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155°C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10°C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (XDI / T-700) containing a second isocyanate group-terminated urethane prepolymer was obtained.

[0153] The solid content concentration of the second isocyanate component (XDI / T-700) was 100%, the isocyanate group content was 10.1% by mass, and the viscosity at 30°C was 17,000 mPa·s. Also, the content ratio of the second raw material polyisocyanate (XDI monomer) to the total amount of the second isocyanate component was 0.10% by mass.

[0154] (Preparation Example 8) Second isocyanate component (XDI / DL-4000) As the second raw material polyisocyanate, 1,3-xylylene diisocyanate (XDI) was used, and as the second raw material polyol, Actocol DL-4000 (trade name, polyether polyol with a number average molecular weight of 4000 and an average number of hydroxyl groups of 2, manufactured by Mitsui Chemicals) was used, and the equivalent ratio (NCO / OH) was set to 10. These were stirred in a nitrogen stream at 70 °C for 6 to 24 hours to cause a urethanization reaction.

[0155] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155 °C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10 °C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (XDI / DL-4000) containing a second isocyanate group-terminated urethane prepolymer was obtained.

[0156] The solid content concentration of the second isocyanate component (XDI / DL-4000) was 100%, the isocyanate group content was 2.02% by mass, and the viscosity at 30 °C was 2800 mPa·s. Also, the content ratio of the second raw material polyisocyanate (XDI monomer) to the total amount of the second isocyanate component was 0.18% by mass.

[0157] (Preparation Example 9) Second isocyanate component (XDI / T-300) As the second raw material polyisocyanate, 1,3-xylylene diisocyanate (XDI) was used, and as the second raw material polyol, Actocol T-300 (trade name, polyether polyol with a number average molecular weight of 300 and an average number of hydroxyl groups of 3, manufactured by Mitsui Chemicals) was used, and the equivalent ratio (NCO / OH) was set to 10. These were stirred in a nitrogen stream at 70 °C for 6 to 24 hours to cause a urethanization reaction.

[0158] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155 °C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10 °C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (XDI / T-300) containing a second isocyanate group-terminated urethane prepolymer was obtained.

[0159] The solid content concentration of the second isocyanate component (XDI / T-300) was 100%, the isocyanate group content was 13.7% by mass, and the viscosity at 30 °C was 84,000 mPa·s. Also, the content ratio of the second raw material polyisocyanate (XDI monomer) to the total amount of the second isocyanate component was 0.12% by mass.

[0160] (Preparation Example 10) Second isocyanate component (XDI / T-5000) As the second raw material polyisocyanate, 1,3-xylylene diisocyanate (XDI) was used, and as the second raw material polyol, Actocol T-5000 (trade name, polyether polyol with a number average molecular weight of 5000 and an average hydroxyl number of 3, manufactured by Mitsui Chemicals) was used, and the equivalent ratio (NCO / OH) was set to 10. These were stirred in a nitrogen stream at 70 °C for 6 to 24 hours to cause a urethanization reaction.

[0161] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature 145 to 155 °C, degree of vacuum 100 Pa or less, flow rate 3 to 5 g / min, cooling water temperature 10 °C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (XDI / T-5000) containing a second isocyanate group-terminated urethane prepolymer was obtained.

[0162] The solid content concentration of the second isocyanate component (XDI / T-5000) was 100%, the isocyanate group content was 2.75% by mass, and the viscosity at 30 °C was 5300 mPa·s. Also, the content ratio of the second raw material polyisocyanate (XDI monomer) to the total amount of the second isocyanate component was 0.11% by mass.

[0163] (Preparation Example 11) Second isocyanate component (XDI / TEG) As the second raw material polyisocyanate, 1,3-xylylene diisocyanate (XDI) was used, and as the second raw material polyol, triethylene glycol (TEG, molecular weight 150.17) was used, and the equivalent ratio (NCO / OH) was set to 10. These were stirred in a nitrogen stream at 70 °C for 6 to 24 hours to cause a urethanization reaction.

[0164] Thereafter, the obtained reaction product was subjected to thin-film distillation (wall temperature: 145 - 155°C, degree of vacuum: 100 Pa or less, flow rate: 3 - 5 g / min, cooling water temperature: 10°C). Otherwise, in the same manner as in Preparation Example 3, a second isocyanate component (XDI / TEG) containing a urethane prepolymer having a second isocyanate group at the terminal was obtained.

[0165] The solid content concentration of the second isocyanate component (XDI / TEG) was 100%, and the isocyanate group content was 16.4% by mass. Also, the content ratio of the second raw material polyisocyanate (XDI monomer) to the total amount of the second isocyanate component was 0.28% by mass. Incidentally, the second isocyanate component (XDI / TEG) gelled after 3 days. Therefore, the viscosity of the second isocyanate component (XDI / TEG) was not measured.

[0166] Examples 1 - 13 and Comparative Examples 1 - 7 With the formulations described in Tables 1 - 3, the first isocyanate component, the second isocyanate component, and the third isocyanate component were mixed. Thereby, a polyisocyanate component (main agent) was obtained. Incidentally, in Comparative Examples 1 - 2, the second isocyanate component was not mixed.

[0167] Also, in Comparative Example 6, since the second isocyanate component (XDI / TEG) had gelled, the polyisocyanate component (main agent) could not be prepared.

[0168] Also, in Comparative Example 7, crude MDI (trade name: Cosmonate M - 200, manufactured by Mitsui Chemicals, polymethylene polyphenyl polyisocyanate with an NCO content of 31.3% by mass) was mixed as the second isocyanate component.

[0169] Also, with the formulations described in Tables 1 to 3, Actocol EP-330N (manufactured by Mitsui Chemicals, Inc.) and 1,4-butanediol were mixed, and 1500 ppm of a catalyst (DABCO 33-LV) was added to the mixture. Thereby, a polyol component (hardener) was obtained. Actocol EP-330N is a block copolymer of propylene oxide - ethylene oxide (ethylene oxide content (terminal oxyethylene group content): 15% by mass, number average molecular weight: 5000, average functionality: 3, hydroxyl value: 34 mgKOH / g).

[0170] Thereby, a structural polyurethane adhesive comprising a polyisocyanate component and a polyol component was obtained.

[0171] (Evaluation) 1. Adhesion test (Examples 1 to 9, Comparative Example 1, and Comparative Examples 3 to 7: PP / SPCC) Test pieces of polypropylene plates (J707G, manufactured by Prime Polymer Co., Ltd. (PP)) cut to a width of 25 mm were prepared. These were corona-treated immediately before preparing the adhesion test specimens, and the wettability (JIS K 6768 (1999)) was adjusted to 40 dyn / cm or more to obtain adherend 1.

[0172] On the other hand, cold-rolled steel sheets (SPCC) were cut to a width of 25 mm, and ED-SPCC plates (JIS G 3141 (SPCC, SD), manufactured by Test Piece Co., Ltd.) subjected to cationic electrodeposition coating (ED) were prepared. Next, the surface of the SPCC was degreased and washed with isopropyl alcohol, and then dried. This was used as adherend 2.

[0173] Then, the polyisocyanate component and the polyol component were mixed at a ratio such that the equivalent ratio (NCO / OH) was 1.05. Next, glass beads (ASGB-60, manufactured by AS ONE Corporation, 0.250 to 0.355 mm) for adjusting the layer thickness were added to the obtained mixture. The addition amount of the glass beads was adjusted to be 1% by mass based on the total amount of the polyisocyanate component, the polyol component, and the glass beads.

[0174] Thereafter, the above mixture was applied to adherend 1, and adherend 1 and adherend 2 were brought into close contact with each other so that the adhesion area was 25 mm × 12.5 mm and the adhesive layer thickness was 0.3 mm, and then cured at 50°C for 20 minutes and cured at room temperature (18 - 28°C, 45 - 55% RH) for 1 week. Thereby, an adhered test piece (hereinafter, test plate) was obtained.

[0175] Then, the shear adhesion strength (hereinafter, adhesion strength) [MPa] between adherend 1 and adherend 2 was measured with a tensile testing machine (U-4410, manufactured by Orientec Co., Ltd.) at a tensile speed of 50 mm / min.

[0176] In addition, the failure state of the adhesive was visually observed and evaluated according to the following criteria. ○: Cohesive failure or surface failure of polypropylene (PP) ×: Interfacial peeling

[0177] 2. Adhesion test (Examples 10 - 13 and Comparative Example 2: CFRP / SPCC) CFRP (matte finish) 2.0 × 25 × 100 mm manufactured by Standard Test Pieces Co., Ltd. was prepared. Next, the surface of the CFPR was degreased and cleaned with isopropyl alcohol and then dried. This was used as adherend 1. For the rest, the adhesion strength [MPa] was measured in the same manner as in the above adhesion test (PP / SPCC).

[0178] In addition, the failure state of the adhesive was visually observed and evaluated according to the following criteria. ◎: The area ratio of cohesive failure is 80% or more and 100% or less ○: The area ratio of cohesive failure is 50% or more and less than 80% ×: The area ratio of cohesive failure is less than 50%

[0179]

Table 1

[0180]

Table 2

[0181]

Table 3

[0182] Note that the above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be construed in a limiting manner. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims.

Industrial Applicability

[0183] The structural polyurethane adhesive of the present invention is suitably used for adhering each member in a structure composed of a plurality of members and the like.< / hplc>

Claims

1. A polyurethane adhesive for structural use, containing a polyisocyanate component and a polyol component, wherein the polyisocyanate component contains a first isocyanate component including a first raw material polyisocyanate composed of an aromatic polyisocyanate and a first isocyanate group-terminated urethane prepolymer which is a reaction product of a first raw material polyol containing a macro polyol, a second isocyanate component including a second raw material polyisocyanate composed of an aromatic aliphatic polyisocyanate and / or an aliphatic polyisocyanate and a second isocyanate group-terminated urethane prepolymer which is a reaction product of a second raw material polyol containing a polyether polyol having a number average molecular weight of 160 or more and 4900 or less, and a third isocyanate component including a carbodiimide-modified product of an aromatic polyisocyanate, wherein, with respect to the total amount of the first isocyanate component, the second isocyanate component, and the third isocyanate component, the proportion of the first isocyanate component is 40% by mass or more and 60% by mass or less, the proportion of the second isocyanate component is 2% by mass or more and 35% by mass or less, and the proportion of the third isocyanate component is 28.8% by mass or more and 40% by mass or less.

2. The polyurethane adhesive for structural use according to claim 1, wherein the second raw material polyisocyanate contains at least one selected from the group consisting of xylylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate), and bis(isocyanatomethyl)cyclohexane.

3. The polyurethane adhesive for structural use according to claim 1, wherein the content ratio of the second raw material polyisocyanate is 1.0% by mass or less with respect to the total amount of the second isocyanate component.

4. The polyurethane adhesive for structural use according to claim 1, wherein the second raw material polyol contains a polyether polyol having an average hydroxyl number of 2 or more and 3 or less.

5. The polyurethane adhesive for structural use according to claim 1, which is a two-component curing type adhesive including a main agent containing the polyisocyanate component and a curing agent containing the polyol component.

6. The polyurethane adhesive for structural use according to claim 1, which is a solvent-free adhesive.

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