Two-part urethane-based adhesive

Abstract

Provided is a two-liquid urethane-based adhesive that can suppress the exudation of a liquid component in a second liquid and the decrease in thixotropy of the second liquid, and that has excellent adhesiveness after aging of a cured product. The two-liquid urethane-based adhesive of the present invention has: a first liquid containing a urethane prepolymer having an isocyanate group; and a second liquid containing water, an active hydrogen compound (excluding water) having an active hydrogen that can react with the isocyanate group, and a cellulose nanofiber, each of the first liquid and the second liquid independently containing carbon black and / or an inorganic filler, and the content of the cellulose nanofiber being 0.1 mass% or more and 1.5 mass% or less relative to the content of the water.

Description

Technical Field

[0001] This invention relates to two-component urethane-based adhesives. Background Technology

[0002] In recent years, from the perspective of lightweighting, resin materials (such as olefin resins, fiber-reinforced plastic (FRP) matrix resins, etc.) have been used to replace steel plates in automobile bodies.

[0003] For bonding such resin materials to dissimilar materials (e.g., glass), to date, two-component curing urethane adhesive compositions comprising a main agent containing a urethane prepolymer and a curing agent have been proposed.

[0004] For example, in Patent Document 1, with the aim of providing an adhesive composition with excellent curing properties and adhesion manifestation, a two-component urethane adhesive composition is described, consisting of a main agent containing a urethane prepolymer, water, and a curing agent containing a compound with two or more functions and containing active hydrogen.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-31483 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Referring to Patent Document 1, the inventors have prepared and evaluated a two-liquid urethane-based adhesive composition comprising a main agent (first liquid) and a curing agent (meaning curing agent in a broad sense, also called second liquid), wherein the second liquid contains an active hydrogen compound such as a polyol, a filler (carbon black and / or inorganic filler; sometimes carbon black and inorganic filler are collectively referred to as "filler"), and water. It should be noted that, generally, in urethane-based adhesive compositions, the active hydrogen compound used as a curing component (curing agent in a narrow sense) for the urethane prepolymer is usually liquid at room temperature (around 23°C).

[0010] The results of the above evaluation show that sometimes, liquid components (which include water and / or active hydrogen compounds formulated in the second liquid) slowly seep out of the second liquid over time.

[0011] In detail, the inventors have confirmed the following phenomenon: if the second liquid containing water or the like is placed in a relatively high temperature environment (e.g., around 40°C) for a long period of time (e.g., around 6 months) as described above, even if the second liquid is stored in a sealed state, water or the like slowly seeps out over time near the surface of the second liquid (not the interior of the second liquid but the interface between the air and the second liquid).

[0012] In addition, it has been found that, as mentioned above, by storing the second liquid containing active hydrogen compounds, fillers, and water for an extended period (e.g., for 6 months under closed conditions at 40°C), the thixotropy of the second liquid sometimes decreases over time.

[0013] It is believed that, as mentioned above, the seepage of liquid components in the second liquid and the reduction of thixotropy in the second liquid are the causes of poor curing during mixing and curing with the first liquid.

[0014] In addition, since the cured product of the two-component urethane adhesive composition is used for a long time, the adhesion after aging is required.

[0015] Therefore, the object of the present invention is to provide a two-component urethane adhesive that can suppress the seepage of liquid components in the second liquid and the reduction of the thixotropy of the second liquid, and the resulting cured product has excellent adhesion after aging.

[0016] Methods for solving problems

[0017] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by including cellulose nanofibers (CNF) in a second liquid within a specific range, the desired effect was obtained, thus completing the present invention.

[0018] Based on the above understanding, the present invention specifically solves the above-mentioned problems through the following configuration.

[0019] [1] A two-component urethane adhesive comprising: a first liquid containing a urethane prepolymer having isocyanate groups; and a second liquid containing water, an active hydrogen compound having active hydrogen that can react with isocyanate groups (excluding water), and cellulose nanofibers.

[0020] The first liquid and the second liquid mentioned above each independently contain carbon black and / or inorganic fillers.

[0021] The content of the aforementioned cellulose nanofibers is 0.1% by mass or more and 1.5% by mass or less relative to the content of the aforementioned water.

[0022] [2] According to the two-component urethane adhesive described in [1], wherein the urethane prepolymer has at least a polyether backbone.

[0023] The aforementioned active hydrogen compounds include polyether polyols.

[0024] [3] According to the two-component urethane adhesive of [1] or [2], wherein the molar ratio of the number of moles (A) of the urethane prepolymer in the first liquid to the number of moles (B) of the active hydrogen in the active hydrogen compound in the second liquid is 0.1 or more and less than 1.0.

[0025] [4] A two-component urethane adhesive according to any one of [1] to [3], wherein the first liquid and the second liquid each independently further comprise a tertiary amine compound and a tin-based or bismuth-based metal complex.

[0026] [5] A two-component urethane adhesive according to any one of [1] to [4], wherein the content of the water is 0.1 to 3.0% by mass of the second liquid.

[0027] [6] A two-component urethane adhesive according to any one of [1] to [5], wherein the first liquid and the second liquid each independently comprise the carbon black and at least one selected from calcium carbonate and silicon dioxide as the inorganic filler.

[0028] The effects of the invention

[0029] The two-component urethane adhesive of the present invention can suppress the seepage of liquid components in the second liquid and the reduction of thixotropy of the second liquid, resulting in excellent adhesion of the cured product after aging. Detailed Implementation

[0030] The present invention will now be described in detail.

[0031] It should be noted that in this specification, (meth)acrylic acid means acrylic acid or methacrylic acid.

[0032] In addition, in this specification, the numerical range indicated by “~” means the range of values ​​included before and after “~” as the lower and upper limits.

[0033] In this specification, unless otherwise specified, each component can be used individually with a substance equivalent to that component, or in combination of two or more substances. When a component contains two or more substances, the content of the component refers to the total content of the two or more substances.

[0034] In this specification, the superiority of at least one of the following is referred to as the superiority of the effect of the present invention: the superiority of the inhibition of seepage of liquid components in the second liquid, the inhibition of the reduction of thixotropy of the second liquid, and the superior adhesion of the cured product after aging.

[0035] [Two-component urethane adhesive]

[0036] The two-component urethane-based adhesive of the present invention (the adhesive of the present invention) is a two-component urethane-based adhesive (a two-component urethane-based adhesive composition) having:

[0037] A first liquid comprising a urethane prepolymer having isocyanate groups; and

[0038] A second liquid comprising water, an active hydrogen compound (excluding water) having active hydrogen that can react with isocyanate groups, and cellulose nanofibers (CNF).

[0039] The first liquid and the second liquid mentioned above each independently contain carbon black and / or inorganic fillers.

[0040] The content of the aforementioned cellulose nanofibers is 0.1% by mass or more and 1.5% by mass or less relative to the content of the aforementioned water.

[0041] The adhesive of the present invention has such a configuration that it is believed to achieve the desired effect. The reason for this is not yet clear, but it is speculated to be roughly as follows.

[0042] The CNF exudation inhibition effect in the second liquid refers to the inhibition effect on exudation phenomena that occur during the storage (preservation) of the second liquid. Exudation phenomena tend to occur in areas near the surface where the mobility of the substances constituting the second liquid (compound composition) is more easily increased [not the interior of the second liquid (compound composition), but the interface between the air and the second liquid (compound composition)]. Due to compatibility issues between the constituent substances [filler (carbon black and / or inorganic filler), water, and active hydrogen compounds with active hydrogen that can react with isocyanate groups (usually liquid substances at room temperature, such as polyols, as mentioned above), liquid components (especially low molecular weight liquid components) slowly exudate from the surface over time.

[0043] In this invention, it is believed that by containing CNF in the second liquid, the exudation of the above-mentioned liquid components can be suppressed due to the strong hydrophilicity of CNF.

[0044] Furthermore, when using inorganic filler components with high specific gravity (such as calcium carbonate) in the second liquid, it is speculated that the entanglement of CNF fibers can also prevent the sedimentation of the aforementioned inorganic filler components with high specific gravity.

[0045] Secondly, regarding the thixotropy of the second liquid, the thixotropy of the second liquid (in the compound composition) is generally mainly due to the occurrence (low shear rate range) and disappearance (high shear rate range) of interparticle interactions between fillers.

[0046] Regarding the thixotropic properties of the second liquid (compound composition), the filler is weakened due to the slow wetting of the filler components during long-term storage of the second liquid (compound composition) (e.g., about 6 months under closed conditions at 40°C).

[0047] However, in this invention, it has been confirmed that by containing CNF in the second liquid (complex composition) system, the reduction of thixotropy of the second liquid (complex composition) can be suppressed.

[0048] It is speculated that the maintenance of the thixotropy of the second liquid is due to the entanglement of CNF fibers in the second liquid, or that CNF inhibits the filler from being slowly wetted by the liquid components.

[0049] Furthermore, in this invention, it has been confirmed that by using CNF in a specified amount, CNF does not impair the adhesion of the cured product after aging.

[0050] It should be noted that the above mechanism is a conjecture of the inventors, and the mechanism of the present invention is not limited to the above.

[0051] The components contained in the adhesive of the present invention will be described in detail below.

[0052] [Two-component urethane adhesive]

[0053] The adhesive of the present invention is a two-component urethane-based adhesive composition having a first liquid and a second liquid. The adhesive of the present invention, after curing, becomes a cured urethane-based product.

[0054] <<First Liquid>>

[0055] In this invention, the first liquid comprises a urethane prepolymer having isocyanate groups.

[0056] <Carbamate Prepolymer>

[0057] The above-mentioned urethane prepolymers are urethane compounds with isocyanate groups.

[0058] In the above-mentioned urethane prepolymers, there are no particular restrictions on the position of the isocyanate group bond. As one of the preferred methods, the isocyanate group is bonded to the end of the urethane prepolymer.

[0059] As one of the preferred methods, urethane prepolymers can be described as having multiple isocyanate groups.

[0060] As a urethane prepolymer, conventionally known urethane prepolymers can be used. For example, reaction products obtained by reacting a polyisocyanate compound with a compound having two or more active hydrogen groups in one molecule (hereinafter referred to as "active hydrogen compound") in an excess of isocyanate groups relative to active hydrogen groups can be used.

[0061] In this invention, "containing active hydrogen group" means a group that contains active hydrogen. Examples of active hydrogen groups include hydroxyl, amino, and imino groups.

[0062] (Polyisocyanate compounds)

[0063] Regarding the polyisocyanate compounds used in the manufacture of urethane prepolymers, there are no particular limitations as long as they have more than two isocyanate groups in the molecule.

[0064] Examples of polyisocyanate compounds include, for example, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, phenylene diisocyanate (XDI), tetramethylphenylene diisocyanate (TMXDI), benzyltoluidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), and triphenylmethane triisocyanate, which are aromatic polyisocyanate compounds.

[0065] Hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(methyl isocyanate)cyclohexane (H6XDI), dicyclohexylmethane diisocyanate (H 12 Aliphatic (the term aliphatic includes linear, branched, and alicyclic) polyisocyanates such as MDI;

[0066] These are carbodiimide-modified polyisocyanates.

[0067] Polyisocyanate compounds can be used individually or in combination of two or more.

[0068] Among these, aromatic polyisocyanate compounds are preferred due to their excellent curability, and MDI is more preferred.

[0069] (Active hydrogen compounds)

[0070] There are no particular limitations on compounds (active hydrogen compounds) having two or more active hydrogen groups per molecule used in the manufacture of urethane prepolymers. Examples of active hydrogen groups include, for example, hydroxyl (OH) groups, amino groups, and imino groups.

[0071] Examples of the aforementioned active hydrogen compounds include, for example, polyol compounds having two or more hydroxyl (OH) groups in one molecule, and polyamine compounds having two or more amino and / or imino groups in one molecule. Among these, polyol compounds are preferred.

[0072] The aforementioned polyol compounds are not particularly limited as long as they have two or more OH groups. Specific examples of polyol compounds include polyether polyols; polyester polyols; (meth)acrylic acid polyols; polybutadiene polyols, hydrogenated polybutadiene polyols; low molecular weight polyols; and mixed polyols of these. Among these, polyether polyols are preferred.

[0073] Regarding polyether polyols, there are no particular restrictions as long as the main chain (backbone) contains polyether and has two or more hydroxyl groups. A polyether is a group having two or more ether bonds; for example, compounds with a total of two or more structural units (-R) can be listed. a -OR b - groups. Wherein, in the above structural unit, R a and R b Each can be represented independently by a hydrocarbon group. There are no particular restrictions on the hydrocarbon group. For example, straight-chain alkylene groups with 1 to 10 carbon atoms and branched alkylene groups with 3 to 10 carbon atoms can be listed.

[0074] Examples of polyether polyols include, for example, polyoxyethylene glycol (polyethylene glycol); polyoxypropylene glycol (polypropylene glycol: PPG); polyoxypropylene triol; polyoxyethylene tetraol; polyols of copolymers of ethylene oxide / propylene oxide; polytetramethylene ether glycol (PTMEG), polytetraethylene glycol, sorbitol polyols, etc.

[0075] Regarding the polyether polyols used in the manufacture of urethane prepolymers, polypropylene glycol and polyoxypropylene triol are preferred from the viewpoint of excellent compatibility with polyisocyanate compounds.

[0076] Regarding the weight-average molecular weight of the polyether polyol, from the viewpoint that the viscosity of the urethane prepolymer obtained by reaction with isocyanate compounds has moderate fluidity at room temperature, a value of 500 to 20,000 is preferred. In this invention, the above-mentioned weight-average molecular weight is a converted value of polystyrene obtained by the GPC method (solvent: tetrahydrofuran (THF)).

[0077] Active hydrogen compounds can be used individually or in combination of two or more.

[0078] Regarding urethane prepolymers, from the viewpoint of achieving better results according to the present invention, it is preferable to have at least a polyether backbone in addition to isocyanate groups. The aforementioned polyether backbone can, for example, be derived from the aforementioned polyether polyol, which is an active hydrogen compound.

[0079] From the viewpoint of achieving better results with respect to urethane prepolymers, urethane prepolymers formed by reacting polyether polyols with aromatic polyisocyanate compounds are preferred.

[0080] Carbamate prepolymers can be used individually or in combination of two or more.

[0081] (Content of carbamate prepolymer)

[0082] Regarding the content of the aforementioned urethane prepolymer, from the viewpoint of achieving better results in this invention, it is preferably 5 to 90% by mass in the first liquid, more preferably 20 to 70% by mass.

[0083] There are no particular limitations on the method for manufacturing urethane prepolymers. For example, urethane prepolymers can be manufactured by reacting a polyisocyanate compound with 1.5 to 2.5 moles of isocyanate groups relative to 1 mole of an active hydrogen compound containing active hydrogen groups (e.g., hydroxyl groups) by mixing and reacting them.

[0084] Carbamate prepolymers may contain unreacted polyisocyanate compounds.

[0085] Plasticizers may be used when manufacturing urethane prepolymers as described above. There are no particular limitations on the type of plasticizer, as long as it is a compound that is non-reactive to polyisocyanate compounds, active hydrogen compounds, and urethane prepolymers, and that can plasticize the reaction system.

[0086] Examples of plasticizers include, for example, diisononyl phthalate (DINP) and dioctyl adipate.

[0087] Regarding the content of the aforementioned plasticizer, from the viewpoint of achieving better results with the present invention, 5 to 20% by mass in the first liquid is preferred.

[0088] Plasticizers used in the manufacture of urethane prepolymers may also be included in the first liquid.

[0089] In this invention, for the purpose of urethane prepolymers, one of the preferred methods is to avoid using blocked isocyanate compounds (compounds in which isocyanate groups are blocked by a blocking agent).

[0090] (Isocyanate group content)

[0091] Regarding the content of the isocyanate groups in the above-mentioned urethane prepolymer, from the viewpoint of achieving better results in this invention, it is preferable to have 0.5 to 5.0% by mass of the total amount of urethane prepolymer.

[0092] When the first liquid also contains a plasticizer, from the viewpoint of better performance of the present invention, the content of the isocyanate groups in the above-mentioned urethane prepolymer is preferably 0.4 to 4.5 by mass of the total of the urethane prepolymer and the plasticizer.

[0093] (Method for determining the content of isocyanate groups)

[0094] The content of isocyanate groups in urethane prepolymers can be determined by potentiometric titration using Method A according to JIS K1603-1:2007.

[0095] When the urethane prepolymer is a mixture with plasticizers, the content of isocyanate groups in the mixture can be determined by potentiometric titration using method A according to JIS K1603-1:2007.

[0096] <<Second Liquid>>

[0097] In this invention, the second liquid comprises water, an active hydrogen compound (excluding water) having active hydrogen that can react with isocyanate groups, and cellulose nanofibers.

[0098] In the crosslinking (formation of urea bonds) between water-induced urethane prepolymers, carbon dioxide-induced foaming generally occurs.

[0099] In this invention, the second liquid contains, in addition to water, an active hydrogen compound that is more reactive with isocyanate groups than water, thus suppressing the foaming and providing excellent adhesion.

[0100] <Water>

[0101] There are no particular restrictions on the water content in the second liquid. For example, tap water or distilled water can be used.

[0102] (Water content)

[0103] Regarding the water content, from the viewpoint of achieving better results with the present invention, it is preferable to have 0.1 to 3.0% by mass in the second liquid.

[0104] Furthermore, regarding the water content, from the viewpoint of achieving better results with the present invention, it is preferably 1.0% by mass or less of the total amount of the adhesive of the present invention, more preferably 0.01 to 0.5% by mass.

[0105] Furthermore, regarding the water content, from the viewpoint of achieving better results with respect to the present invention, it is preferably 2.0 parts by mass or less, and more preferably 0.02 to 1.0 parts by mass, relative to 100 parts by mass of the urethane prepolymer.

[0106] <Active Hydrogen Compounds>

[0107] In this invention, the second liquid contains an active hydrogen compound having active hydrogen that can react with isocyanate groups. However, water is excluded from the aforementioned active hydrogen compound. Furthermore, the active hydrogen compound having active hydrogen that can react with isocyanate groups does not contain cellulose nanofibers.

[0108] The active hydrogen compound described above possesses the aforementioned active hydrogen, enabling it to react with the isocyanate groups present in the urethane prepolymer.

[0109] The active hydrogen compound is preferably a liquid at room temperature (23°C).

[0110] (Active hydrogen that can react with isocyanate groups)

[0111] The above-mentioned active hydrogen compounds preferably have multiple active hydrogen atoms per molecule that can react with isocyanate groups.

[0112] Regarding the active hydrogen in the aforementioned active hydrogen compounds that can react with isocyanate groups, for example, they can form active hydrogen groups such as hydroxyl, amino, and imino groups.

[0113] Examples of the aforementioned active hydrogen compounds include, for example, polyol compounds having two or more hydroxyl groups (-OH) in one molecule, and polyamine compounds having two or more amino groups (-NH2) and / or imino groups (-NH-) in one molecule. Among these, polyol compounds are preferred.

[0114] Regarding the aforementioned polyol compounds, there are no particular limitations as long as they have two or more OH groups. Specific examples of polyol compounds include polyether polyols; polyester polyols; (meth)acrylic acid polyols; polybutadiene polyols, hydrogenated polybutadiene polyols; low molecular weight polyols; and mixed polyols of these.

[0115] Regarding the aforementioned active hydrogen compounds, from the viewpoint of achieving better results according to the present invention, it is preferable to include polyether polyols.

[0116] Regarding the polyether polyol contained in the second liquid as an active hydrogen compound, it can be the same as the polyether polyol used as an active hydrogen compound in the manufacture of the aforementioned urethane prepolymer.

[0117] In addition, the polyether polyol contained in the second liquid as an active hydrogen compound may also have nitrogen atoms in its main chain structure.

[0118] Regarding the polyether polyols contained in the second liquid as active hydrogen compounds, from the viewpoint of better performance of the present invention, it is preferable to include polyether triol and / or polyether tetraol, and more preferably polyether triol and polyether tetraol.

[0119] (Polyethertriol)

[0120] As a polyether triol (a trifunctional polyether polyol), for example, compounds having three hydroxyl groups in one molecule and a polyether backbone can be listed.

[0121] As polyether triols, specifically, for example, polyoxyethylene triols and polyoxypropylene triols such as polyoxyethylene triols can be listed.

[0122] Regarding the content of polyether triol, from the viewpoint of achieving better results in this invention, it is preferable to have 80% or more by mass of the total amount of the above-mentioned active hydrogen compounds, more preferably 85 to 98% by mass.

[0123] (Polyethertetraol)

[0124] As a polyether tetraol (a 4-functional polyether polyol), for example, compounds having four hydroxyl groups in one molecule and a polyether as the backbone can be listed. Polyether tetraols may further have nitrogen atoms in their main chain structure.

[0125] As a polyether tetraol, for example, polyoxyethylene tetraol, a compound represented by the following formula (4) can be listed.

[0126] [Chemistry 1]

[0127]

[0128] In formula (4), R6 to R9 each independently represent propylidene and / or ethylidene, R 10 It represents an alkylene group having 2 to 10 carbon atoms, where a to d each independently represent 1 to 10. At least one of a to d has 3 or more carbon atoms.

[0129] Examples of alkylene groups having 2 to 10 carbon atoms include ethylene, tetramethylene, pentylene, hexylene, octylene, and decylene. Ethylene is preferred among the alkylene groups having 2 to 10 carbon atoms.

[0130] For polyethers that form the backbone, for example, in formula (4) where a is 3 or more, H-(O-R6) a - This becomes a polyether with hydroxyl groups at the ends. The same applies to b to d.

[0131] Regarding the polyether tetraol contained in the second liquid as an active hydrogen compound, from the viewpoint of better effects of the present invention, it is preferable to include a compound having nitrogen atoms in the main chain structure, and more preferably a compound represented by the above formula (4).

[0132] In terms of the weight-average molecular weight of the polyether tetraol, from the viewpoint of achieving better results in this invention, it is preferably 200 to 2,000, and more preferably 400 to 800.

[0133] In this invention, the weight-average molecular weight of active hydrogen compounds (such as polyols like the aforementioned polyether tetraol) can be set as the polystyrene equivalent value obtained using gel permeation chromatography with the solvent THF (tetrahydrofuran). The method and conditions for determining the weight-average molecular weight of active hydrogen compounds in this invention are described below.

[0134] (Methods and conditions for determining the weight-average molecular weight of active hydrogen compounds)

[0135] GPC: LC Solution (manufactured by SHIMAZU)

[0136] Detector: SPD-20A (manufactured by SHIMAZU)

[0137] Column: Connect two Shim-pack GPC-801 (manufactured by SHIMAZU) wires in series.

[0138] Solvent: Tetrahydrofuran

[0139] Temperature: 40℃

[0140] Flow rate: 0.5 ml / min

[0141] Concentration: 2mg / ml

[0142] Standard sample: polystyrene

[0143] Regarding the content of polyether tetraol, from the viewpoint of achieving better results in this invention, it is preferable to have 20% or less by mass of the total amount of the aforementioned active hydrogen compounds, more preferably 1 to 10% by mass.

[0144] Monoether polyols

[0145] In cases where the aforementioned active hydrogen compound contains polyether polyols, the aforementioned active hydrogen compound may further contain monoether polyols.

[0146] Monoether polyols are compounds having multiple hydroxyl groups and at least one ether bond. However, the ether bonds in monoether polyols do not form a polyether backbone.

[0147] Monoether polyols preferably have 3 to 4 hydroxyl groups per molecule.

[0148] Monoether polyols can have 1 to 4 ether bonds per molecule.

[0149] As monoether polyols, for example, compounds represented by the following formula (5) can be listed.

[0150] [Chemistry 2]

[0151]

[0152] In equation (5), R 56 ~R 59 Each independently represents propylidene and / or ethylidene, R 50 The alkylene groups have 2 to 10 carbon atoms, and each of the groups a to d independently represents 1 to 2. At least one of a to d is 2.

[0153] Examples of alkylene groups having 2 to 10 carbon atoms include ethylene, tetramethylene, pentylene, hexylene, octylene, and decylene. Ethylene is preferred among the alkylene groups having 2 to 10 carbon atoms.

[0154] In terms of the weight-average molecular weight of the monoether polyol, from the viewpoint of achieving better results in this invention, it is preferably 100 to 1,000, and more preferably 200 to 500.

[0155] Regarding the content of monoether polyols, from the viewpoint of achieving better results in this invention, it is preferable to have 0 to 10% by mass of the total amount of the above-mentioned active hydrogen compounds, more preferably 1 to 10% by mass.

[0156] (Molar ratio B / A)

[0157] From the viewpoint of achieving better results, the molar ratio (B / A) of the isocyanate groups (A) of the urethane prepolymer in the first liquid of the adhesive of the present invention to the molar ratio (B) of the active hydrogen (B) of the active hydrogen compound in the second liquid of the adhesive of the present invention is preferably 0.1 or more and less than 1.0, more preferably 0.2 to 0.5.

[0158] <Cellulose Nanofibers>

[0159] In this invention, the second liquid contains cellulose nanofibers (CNF).

[0160] Regarding the thickness of the cellulose nanofibers, from the viewpoint of achieving better results in this invention, a thickness of 100 nm or less is preferred, and 3 to 10 nm is more preferred.

[0161] Regarding the length of the cellulose nanofibers, from the viewpoint of achieving better results in this invention, 0.5 to 50 μm is preferred.

[0162] To determine the thickness of cellulose nanofibers, moistened cellulose nanofibers were filtered, desolventized, and yielded fine fiber sheets. These sheets were then freeze-dried in liquid nitrogen and observed using a scanning electron microscope (SEM) at magnifications ranging from 100 to 10,000. The average width of 50 fibers observed in the above observations was taken as the thickness of the cellulose nanofibers.

[0163] Regarding the length of cellulose nanofibers, the same method was used to observe cellulose nanofibers as described above, and the average length of 50 fibers was taken as the length of the cellulose nanofiber.

[0164] Regarding CNFs, from the viewpoint of achieving better results according to the present invention, it is preferable to have functional groups, and more preferably, carboxyl groups. The aforementioned carboxyl groups can form carboxyl ions or salts (e.g., sodium salts).

[0165] In the case where CNF has functional groups, in addition to the aforementioned functional groups, CNF may also have hydroxyl and / or hydroxymethyl groups derived from cellulose.

[0166] There are no particular limitations on the manufacturing method of CNF. For example, conventionally known manufacturing methods can be cited. As a method for manufacturing cellulose fibers with functional groups in CNF, for example, the following method can be cited: using raw cellulose (e.g., raw cellulose fiber) that does not have functional groups, at least some or all of the hydroxyl groups in the raw cellulose are replaced with the aforementioned functional groups using conventionally known methods.

[0167] <Content of cellulose nanofibers>

[0168] In this invention, the content of cellulose nanofibers is 0.1% by mass or more and 1.5% by mass or less relative to the content of water.

[0169] Regarding the content of cellulose nanofibers, from the viewpoint of achieving better results in this invention, it is preferably 0.1 to 1.2% by mass relative to the water content mentioned above.

[0170] As a form of CNF, for example, a mixture containing CNF and water can be listed.

[0171] In this invention, when CNF is the mixture described above, the content of the cellulose nanofibers described above means the content of net cellulose nanofibers in the mixture described above.

[0172] <Carbon black and / or inorganic fillers>

[0173] In this invention, the first liquid and the second liquid each independently contain carbon black and / or inorganic fillers. It should be noted that carbon black is excluded from the aforementioned inorganic fillers.

[0174] (Carbon black)

[0175] There are no particular restrictions on the types of carbon black that can be independently contained in the first and second liquids. Examples include SAF (Super Abrasion Furnace), ISAF (Intermediate Super Abrasion Furnace), HAF (High Abrasion Furnace), FEF (Fast Extruding Furnace), GPF (General Purpose Furnace), and SRF (Semi-Reinforcing Furnace).

[0176] (Inorganic packing)

[0177] Inorganic fillers that can be independently contained in the first and second liquids include, for example, calcium carbonate, silica, talc, and mica. Surface treatment can be applied to the inorganic fillers. There are no particular limitations on the surface treatments described above.

[0178] In cases where the first liquid and the second liquid each independently contain inorganic fillers, from the viewpoint of achieving better results in this invention, the inorganic fillers preferably contain calcium carbonate and / or silicon dioxide.

[0179] From the viewpoint of achieving better results with the present invention, it is preferable that the first liquid and the second liquid each independently comprise the carbon black and at least one selected from calcium carbonate and silicon dioxide as the inorganic filler. (That is, from the viewpoint of achieving better results with the present invention, it is preferable that the first liquid and the second liquid each independently comprise at least one selected from carbon black, calcium carbonate, and silicon dioxide.)

[0180] From the viewpoint of achieving better results with the present invention, it is preferable that the first liquid contains carbon black and inorganic filler, and more preferably contains carbon black and calcium carbonate.

[0181] When the first liquid contains carbon black, from the viewpoint of better performance of the present invention, 10 to 30% by mass of the first liquid is preferred in terms of the content of carbon black.

[0182] When the first liquid contains inorganic filler, from the viewpoint of better effect of the present invention, 10 to 30% by mass of the first liquid is preferred in terms of the content of the inorganic filler.

[0183] When the first liquid contains carbon black and inorganic fillers, the carbon black content is the same as described above, and the inorganic filler content is the same as described above.

[0184] Regarding the second liquid, from the viewpoint of achieving better results according to the present invention, it is preferable to include an inorganic filler, more preferably calcium carbonate and / or silicon dioxide, and further preferably calcium carbonate and silicon dioxide.

[0185] When the second liquid contains inorganic fillers, from the viewpoint of better performance of the present invention, 10 to 35% by mass of the first liquid is preferred in terms of the content of the inorganic fillers.

[0186] In the second liquid, from the viewpoint of achieving better results with respect to the content of carbon black, it is preferable to have 0 to 30% by mass in the second liquid.

[0187] (catalyst)

[0188] From the viewpoint of achieving better results with respect to the first liquid and the second liquid, it is preferable that each of them also independently contains a catalyst.

[0189] The catalyst described above can promote the reaction between the urethane prepolymer in the first liquid and the active hydrogen compound or water in the second liquid.

[0190] Furthermore, regarding the first and second liquids, from the viewpoint of achieving better results according to the present invention, it is preferable that each of them independently contains a tertiary amine compound and a tin-based or bismuth-based metal complex as a catalyst.

[0191] ·Tertiary amine compounds

[0192] Tertiary amine compounds are compounds with a tertiary amino group (three carbon atoms bonded to a nitrogen atom, and the nitrogen atom not bonded to a hydrogen atom).

[0193] Examples of tertiary amine compounds include, for example, 1,4-diazabicyclo[2.2.2]octane, 2,4,6-tris(dimethylaminomethyl)phenol, 2-methyltriethylenediamine, and compounds containing a dimorpholinodiethyl ether structure.

[0194] From the viewpoint of achieving better results with respect to tertiary amine compounds, it is preferable to include a dimorpholinodiethyl ether structure.

[0195] The dimorpholine diethyl ether structure is a structure with dimorpholine diethyl ether as the basic framework.

[0196] In the dimorpholine diethyl ether structure, the hydrogen atoms of the morpholine ring can also be substituted with substituents. There are no particular limitations on the substituents. For example, alkyl groups can be listed. Examples of alkyl groups include methyl and ethyl groups.

[0197] As an amine catalyst containing a dimorpholinodiethyl ether structure, for example, compounds represented by the following formula (9) can be listed.

[0198] [Chemistry 3]

[0199]

[0200] In equation (9) above, R 1 R 2 Each is an alkyl group, and m and n are each 0, 1, or 2.

[0201] As an amine catalyst containing a dimorpholino diethyl ether structure, examples include, for instance, dimorpholino diethyl ether (DMDEE), di(methylmorpholino)diethyl ether, and di(dimethylmorpholino)diethyl ether.

[0202] Regarding tertiary amine compounds, from the viewpoint of achieving better results in this invention, it is preferable to include dimorpholinodiethyl ether (DMDEE) and / or 2-methyltriethylenediamine.

[0203] (Tin-based metal complexes)

[0204] Tin-based metal complexes that act as catalysts for tin include, for example, tin carboxylic esters such as dimethyltin dilaurate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin diacetate, and tin octoate.

[0205] (bismuth-based metal complexes)

[0206] Regarding bismuth-based metal complexes that serve as catalysts for bismuth, examples include bismuth carboxylic acid esters such as bismuth octoate (specifically, bismuth trioctoate, for example).

[0207] Regarding the first liquid, from the viewpoint of achieving better results according to the present invention, it is preferable to include a tertiary amine compound and a bismuth-based metal complex, more preferably to include an amine catalyst containing a dimorpholinodiethyl ether structure and a bismuth-based metal complex, and even more preferably to include DMDEE and a bismuth-based metal complex.

[0208] Regarding the second liquid, from the viewpoint of achieving better results according to the present invention, it is preferable to include a tertiary amine compound and a tin-based metal complex, and more preferably to include 2-methyltriethylenediamine and dibutyltin dilaurate.

[0209] When the first liquid contains a catalyst, the content of the catalyst can be appropriately selected. For example, the content of the catalyst can be set to 1% by mass or less of the total volume of the first liquid. The same applies to the content of the catalyst in the total volume of the second liquid when the second liquid contains a catalyst.

[0210] (Any other ingredients)

[0211] With regard to the adhesive of the present invention, additives may be further contained as needed, without prejudice to the purpose of the present invention.

[0212] Examples of such additives include, for example, plasticizers, anti-aging agents, antioxidants, silane coupling agents, thickeners, ultraviolet absorbers, flame retardants, and surfactants.

[0213] The content of the above-mentioned additives, or whether the above-mentioned additives are added to the first liquid or the second liquid, can be appropriately selected.

[0214] Plasticizers

[0215] Examples of plasticizers include diisononyl phthalate (DINP); dioctyl adipate, isodecyl succinate; diethylene glycol dibenzoate, pentaerythritol ester; butyl oleate, methyl acetylacetonate; tricresyl phosphate, trioctyl phosphate; propylene glycol adipate, butylene glycol adipate, etc. These can be used individually or in combination of two or more.

[0216] (Manufacturing method)

[0217] There are no particular limitations on the manufacturing method of the adhesive of the present invention. For example, it can be manufactured by placing the components contained in the first liquid and the components contained in the second liquid into different containers and mixing the containers under a nitrogen atmosphere.

[0218] As a method of using the adhesive of the present invention, it is sufficient to mix the first liquid and the second liquid described above. There are no particular limitations on the method of mixing the first liquid and the second liquid. For example, conventionally known methods can be cited.

[0219] Regarding the mixing ratio of the first liquid to the second liquid (mass ratio of the first liquid to the second liquid), from the viewpoint of achieving better results in this invention, a ratio of 10:0.5 to 2.0 is preferred.

[0220] (Substrate)

[0221] Examples of substrates for which the adhesive of the present invention can be applied include plastics, glass, rubber, and metals.

[0222] In terms of substrate, substrates containing olefin resins are preferred.

[0223] The substrate containing olefin resin can be a substrate obtained from a mixture of olefin resin and filler. Examples of fillers include, for example, carbon fiber, glass filler such as glass, talc, calcium carbonate, or alumina.

[0224] Plastics can be homopolymers, copolymers, or hydrides. The same applies to rubber.

[0225] Specific examples of plastics include olefin resins such as polypropylene, polyethylene, ethylene-propylene copolymer, COP (cyclic olefin polymer), and COC (cyclic olefin copolymer);

[0226] Polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT);

[0227] Polymethyl methacrylate resin (PMMA resin); polycarbonate resin; polystyrene resin; acrylonitrile-styrene copolymer resin; polyvinyl chloride resin; acetate resin; ABS resin (acrylonitrile butadiene styrene resin); polyamide resin.

[0228] The COC mentioned above refers to cyclic olefin copolymers, such as copolymers of tetracyclic dodecene with olefins like ethylene.

[0229] In addition, the aforementioned COP refers to cyclic olefin polymers, such as polymers obtained by ring-opening polymerization and hydrogenation of norbornene.

[0230] Plastics can also be resins that are difficult to bond.

[0231] Surface treatments can also be applied to the substrate. Examples of surface treatments include flame treatment, corona treatment, and ITRO treatment. There are no particular limitations on the methods used for these surface treatments. For example, methods known in the past can be cited.

[0232] There are no particular limitations on the method of applying the adhesive of the present invention to a substrate. For example, conventionally known methods can be cited.

[0233] The adhesive of the present invention can be cured using water contained in the second liquid, and possibly a catalyst, etc. The adhesive of the present invention can be cured, for example, at 5–90°C and a relative humidity (RH) of 5–95%.

[0234] (use)

[0235] Examples of uses for the adhesives of this invention include, for example, direct glasing ingagent, automotive sealant, and sealant for building components.

[0236] Example

[0237] The following examples illustrate the invention in detail. However, the invention is not limited to these examples.

[0238] <Manufacturing of Two-Flush Carbamate-Based Adhesives>

[0239] (First Liquid)

[0240] For each component in the first liquid column of Table 1 below, mix them using a stirrer according to the composition (parts by mass) shown in the table. Use the resulting mixture as the first liquid.

[0241] (Second liquid)

[0242] For each component in the second liquid column of Table 1 below, mix them using a stirrer according to the composition (parts by mass) shown in the table. Use the resulting mixture as the second liquid.

[0243] It should be noted that for the "Net CNF content (mass%) relative to water content" column of the second liquid, the above "water content" refers to the total water content of the water added to the second liquid and the water contained in the cellulose nanofiber (CNF) content.

[0244] ·Initial second liquid

[0245] Each of the second liquids obtained as described above is used as the initial second liquid.

[0246] ·Second liquid after storage

[0247] A storage test was conducted in which each initial second liquid was placed at 40°C for 6 months to obtain the second liquid after storage.

[0248] <<Evaluation of the Second Liquid>>

[0249] The thixotropy of the initial second liquid and the stored second liquid obtained as described above were evaluated as follows. The results are shown in Table 1.

[0250] The second liquid obtained after storage as described above was evaluated as follows: <leakage of the liquid components of the second liquid>. The results are shown in Table 1.

[0251] <Thixotropy of the Second Liquid>

[0252] (Evaluation methods for thixotropy)

[0253] For each initial second liquid obtained as described above, the viscosity at 1 rpm and 10 rpm was measured using a BS type viscometer and a No.7 rotor at 25°C. The ratio of viscosity at 1 rpm to viscosity at 10 rpm was then calculated from the above measurement results.

[0254] (Evaluation criteria for thixotropy)

[0255] Regarding the thixotropic properties of the initial second liquid, the case where the ratio of viscosity at 1 rpm to viscosity at 10 rpm is 6.5 or higher is evaluated as "excellent initial thixotropic properties" and is indicated as "○".

[0256] The case where the ratio of viscosity at 1 rpm to viscosity at 10 rpm is less than 6.5 is evaluated as "poor initial thixotropy" and is represented as "×".

[0257] For the second liquid after storage, the viscosity was measured in the same way as the initial second liquid, and the same standard as the thixotropic evaluation standard was used for evaluation.

[0258] (Evaluation criteria for the inhibition of the reduction in thixotropy of the second liquid)

[0259] When both the initial viscosity-to-viscosity ratio of the second liquid at 1 rpm and the ... after storage are 6.5 or higher, it is evaluated that the reduction of the thixotropic property of the second liquid can be suppressed.

[0260] When both ratios are 6.5 or higher as described above, the smaller the difference between the initial 1rpm viscosity / 10rpm viscosity ratio of the second liquid and the 1rpm viscosity / 10rpm viscosity ratio of the second liquid after storage, the better it is evaluated as being able to further suppress the decrease in the thixotropy of the second liquid.

[0261] On the other hand, when the ratio of the viscosity of the second liquid at 1 rpm to the viscosity at 10 rpm after storage is less than 6.5, it is evaluated that the decrease in the thixotropy of the second liquid cannot be suppressed.

[0262] It should be noted that when both the initial viscosity ratio of the second liquid at 1 rpm and the viscosity ratio at 1 rpm and the viscosity ratio at 1 rpm and the viscosity ratio at 1 rpm and the viscosity ratio at 10 rpm after storage are less than 6.5, it is evaluated that the original second liquid has poor thixotropy and cannot suppress the decrease in the thixotropy of the second liquid.

[0263] <Leakage of the liquid components of the second liquid>

[0264] The second liquid after storage was observed visually after the above storage test.

[0265] (Evaluation criteria for the leakage of liquid components from the second liquid)

[0266] If no liquid components are found to seep out onto the surface of the second liquid after storage, it is indicated by “○”.

[0267] If leakage of liquid components is found on the surface of the second liquid after storage, it is indicated as "×".

[0268] (Mixing of the first and second solutions)

[0269] Next, the first liquid manufactured as described above and the second liquid manufactured as described above are mixed at the mixing ratio shown in the "First liquid: Second liquid mixing ratio (mass ratio)" column of Table 1 to obtain a mixture of two urethane adhesives.

[0270] It should be noted that the molar ratio (A) of the number of isocyanate groups in the urethane prepolymer in the first liquid and the molar ratio (B) of the number of active hydrogens in the active hydrogen compound in the second liquid when mixed at the above mixing ratio is shown together in the "Molar Ratio B / A" column of Table 1.

[0271] <Preparation of Test Subjects>

[0272] (Initial test subject)

[0273] Prepare a substrate that has been primed with a talc-containing polypropylene resin (trade name TSOP#5, manufactured by Polymer Corporation, 25mm wide, 100mm long, 3mm thick) and has undergone surface treatment (corona treatment).

[0274] Next, on the surface of the substrate that has been primed, apply the mixture of the two-component urethane adhesive to form a triangular strip that is 8mm wide, 100mm long, and 12mm high. Then, place release paper on the strip and flatten the adhesive layer so that it is 3mm thick.

[0275] Then, the initial test specimens were prepared by placing them at 20°C and 65% RH for 3 days.

[0276] (Test specimen after thermal aging)

[0277] • Thermal aging test

[0278] A thermal aging test was conducted on each initial test specimen, which was placed at 90°C for 366 hours to obtain the thermally aged test specimen.

[0279] (Test specimen after hydrothermal aging)

[0280] • Hydrothermal aging test

[0281] A hydrothermal aging test was conducted by immersing each initial test specimen in warm water at 90°C for 366 hours to obtain the hydrothermally aged test specimen.

[0282] <Evaluation of Adhesion>

[0283] For each test specimen manufactured as described above, the adhesive properties were evaluated using the following method. The results are shown in Table 1.

[0284] (Hand peeling test)

[0285] For each test specimen prepared as described above, a manual peel test was conducted according to JASO standard (standard number M338-89) to peel off the adhesive layer formed by the two-component urethane adhesive from each test specimen, and the damage state of each test specimen was visually confirmed.

[0286] Evaluation criteria for initial adhesion

[0287] For the failure state of the above initial bond test specimens after hand peel test, evaluate the CF rate (the proportion of the area of ​​cohesive failure (CF) relative to the total area of ​​the bonded surface. Unit: %).

[0288] • “Excellent initial adhesion”

[0289] In this invention, a case where the initial CF rate of the test specimen is 80% or higher is evaluated as "exceptionally excellent initial adhesion" and is denoted as "◎".

[0290] • "Initial adhesion is slightly better"

[0291] Cases with a CF ratio of 60% or higher but less than 80% are evaluated as having "slightly superior initial adhesion" and are indicated by "○".

[0292] • "Initial adhesion is slightly poor"

[0293] The case where the CF ratio is above 40% but below 60% is evaluated as "slightly poor initial adhesion" and is denoted as "△".

[0294] • "Very poor initial adhesion"

[0295] Cases with a CF rate of less than 40% are evaluated as having "very poor initial adhesion" and are marked as "×".

[0296] For the adhesion of the test specimen after heat aging (adhesion after heat aging), a hand peel test was performed in the same manner as for the initial adhesion described above, and the same evaluation criteria as for the initial adhesion described above were used.

[0297] For the adhesion of the test specimens after hydrothermal aging (adhesion after hydrothermal aging), the same hand peel test was performed as for the initial adhesion mentioned above, and the same evaluation criteria as for the initial adhesion were used.

[0298] (Evaluation criteria for adhesion after aging)

[0299] If the evaluation results of adhesion after thermal aging and adhesion after hydrothermal aging are both 0 or above (CF rate above 60%), the adhesion after aging is evaluated as excellent.

[0300] On the other hand, if at least one or both of the evaluation results of adhesion after thermal aging or adhesion after hydrothermal aging are below △ (CF rate less than 60%), the adhesion after aging is evaluated as poor.

[0301] [Table 1]

[0302]

[0303] The details of each component shown in Table 1 are as follows.

[0304] ((First Liquid))

[0305] • Carbamate prepolymer inclusion: 267g of polyoxypropylene glycol (trade name Exeno 2020, manufactured by AGC) with a hydroxyl value of 56 mg KOH / g and 519g of polyoxypropylene triol (trade name Exeno 3030, manufactured by AGC) with a hydroxyl value of 28 mg KOH / g were mixed with 210g of dioctyl adipate as a plasticizer. Then, 110g of 4,4′-diphenylmethane diisocyanate (MDI) (trade name Sumiju 44S, manufactured by Sumitomo Chemical Co., Ltd.) was added. The mixture was reacted at 80°C for 5 hours to obtain a carbamate prepolymer inclusion containing the carbamate prepolymer and the aforementioned plasticizer. The carbamate prepolymer contained in the above carbamate prepolymer inclusion has isocyanate groups at the ends. The isocyanate group content in the above-mentioned urethane prepolymer is 1.36% by mass.

[0306] • Carbon black: Trade name Niteron #200, manufactured by Shin-Nippon Chemical Co., Ltd.

[0307] • Calcium carbonate 1: Heavy calcium carbonate. Trade name SL-100, manufactured by Takehara Chemical Industry Co., Ltd. Specific surface area 0.8 m² 2 / g

[0308] Plasticizer: Diisononyl phthalate (DINP), manufactured by Jeplastic Co., Ltd.

[0309] Tertiary amine compound 1: Dimorpholino diethyl ether (DMDEE), trade name UCAT-660M, manufactured by SunA Pro Co., Ltd.

[0310] • Bismuth-based metal complex: Bismuth trioctanoate. Trade name: Neostar U-600, manufactured by Nitto Kasei Corporation.

[0311] ((Second liquid))

[0312] (Active hydrogen compounds)

[0313] • Trifunctional polyether polyol: Polyoxypropylene triol. Trade name: Premium 7001K, manufactured by AGC. It has three hydroxyl groups in one molecule. It is a liquid at room temperature (23°C).

[0314] • 4-functional polyether polyol: Trade name Exsenol 450ED, manufactured by AGC Corporation. A compound having four hydroxyl groups in one molecule, represented by the following formula (4). Weight average molecular weight 550. Liquid at room temperature (23°C).

[0315] [Chemistry 4]

[0316]

[0317] In equation (4), R6 to R9 each independently represent propylidene, R 10 The symbol represents ethylene, and a to d each independently represent 1 to 10. At least one of a to d is 3 or more.

[0318] • Monoether polyol: Trade name ADEKA POLYETHER BM-34, manufactured by ADEKA. A compound having four hydroxyl groups in one molecule, represented by the following formula (5). Weight average molecular weight 280. Liquid at room temperature (23°C).

[0319] [Chemistry 5]

[0320]

[0321] In equation (5), R 56 ~R 59 Each independently represents propylidene and / or ethylidene, R 50 The symbol represents ethylene, and a to d each independently represent 1 to 2. At least one of a to d is 2.

[0322] Water: Distilled water

[0323] • Cellulose nanofibers (CNF) contain: Trade name Leocrysta I-2SP, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. CNF content 2% by mass. A mixture of CNF modified with carboxyl groups (which can be carboxyl ions or salts) and water. The CNF thickness is 3 nm, and the CNF length is 1 μm.

[0324] • Calcium carbonate 2: Calcium carbonate with a surface treated with fatty acids. Trade name: Calfin 200, manufactured by Maruo Calsium Co., Ltd.

[0325] • Hydrophilic silica: Trade name Leorosil QS102S, manufactured by Tokuyama Co., Ltd.

[0326] · Tertiary amine compound 2: 2-methyltriethylenediamine (メチルダブコ). Made by エアプロダクツジャパン Company

[0327] Tin-based metal complex: Dibutyltin dilaurate. Neostar U-100, manufactured by Nitto Chemical Corporation.

[0328] As shown in Table 1, Comparative Example 1, which does not contain cellulose nanofibers, failed to suppress the exudation of liquid components in the second liquid and the decrease in the thixotropy of the second liquid. For the stored second liquid of Comparative Example 1, as described above, exudation of liquid components was observed on the surface of the stored second liquid. Gas chromatography (GC) analysis of the exuded liquid components revealed the presence of water and a tetrafunctional polyether polyol.

[0329] In Comparative Example 2, where the content of cellulose nanofibers exceeded the specified range, the second liquid exhibited poor thixotropy and could not suppress the decrease in thixotropy of the second liquid, resulting in poor adhesion of the cured product after aging.

[0330] Compared to the above, the adhesive of the present invention can suppress the seepage of liquid components in the second liquid and the reduction of the thixotropy of the second liquid, resulting in excellent adhesion of the cured product after aging.

Claims

1. A two-component urethane-based adhesive, comprising: A first liquid comprising a urethane prepolymer having isocyanate groups; and The second liquid comprises water, an active hydrogen compound having active hydrogen that can react with isocyanate groups, and cellulose nanofibers, wherein the active hydrogen compound does not include water. The first liquid and the second liquid each independently contain carbon black and / or inorganic fillers, wherein the inorganic fillers do not include carbon black. The content of the cellulose nanofibers is more than 0.1% by mass and less than 1.5% by mass relative to the content of water.

2. The two-component urethane-based adhesive according to claim 1, wherein, The urethane prepolymer has at least a polyether backbone. The active hydrogen compound comprises a polyether polyol.

3. The two-component urethane adhesive according to claim 1 or 2, wherein, The molar ratio of the number of isocyanate groups (A) in the urethane prepolymer in the first liquid to the number of molar active hydrogens (B) in the active hydrogen compound in the second liquid is 0.1 or more and less than 1.

0.

4. The two-component urethane adhesive according to claim 1 or 2, wherein, The first liquid and the second liquid each independently further contain tertiary amine compounds and tin-based or bismuth-based metal complexes.

5. The two-component urethane-based adhesive according to claim 1 or 2, wherein, The water content is 0.1 to 3.0% of the mass of the second liquid.

6. The two-component urethane adhesive according to claim 1 or 2, wherein, The first liquid and the second liquid each independently contain the carbon black, and at least one selected from calcium carbonate and silicon dioxide as the inorganic filler.

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