JP7744749B2 - Moisture-curable adhesive composition - Google Patents

Description

The present invention relates to a moisture-curable adhesive composition that is colorless and highly transparent.

Resins have the ability to be molded into a variety of shapes, and resin molded bodies can be bonded with adhesive compositions to form more complex structures. Therefore, they are widely used as components for constructing a wide variety of products. In particular, colorless and transparent resins are widely used for the exterior surfaces of various products because they allow light to pass through and offer a high level of design flexibility.

In order to combine resins to create complex structures, a commonly used technique is to bond various types of adherends, including resins, together to create structures, and adhesive compositions are used as a means of bonding. Such adhesive compositions include curing adhesives such as room temperature curing adhesives and heat curing adhesives, and moisture curing adhesives, which cure with moisture in the atmosphere, have also been proposed and used in the hope of improving workability. The applicant has also proposed a moisture curing adhesive composition with good usability and adhesive properties (Patent Document 1).

Patent No. 5922985

When an adhesive composition is used to bond a transparent adherend, such as a transparent resin, the adhesive composition becomes visible through the transparent adherend. However, if the adhesive composition has a color, the presence of the adhesive composition can be seen through the transparent adherend due to the color, which can cause a problem of deteriorating the appearance of the adherend, which requires high design quality.

In addition, the adhesive composition may overflow from the edges of the adherend. If the adhesive composition used has a color, the presence of the adhesive composition can be detected by the color, which can cause the appearance of the adherend to deteriorate.

Therefore, there is a demand for adhesive compositions used to bond adherends to be as colorless and transparent as possible, so that the appearance of the adherend after curing is not marred by the color of the adhesive composition.

However, conventional adhesive compositions, such as the moisture-curing adhesive proposed in Patent Document 1, can have a slight yellowish tinge after curing if used in large amounts, which can impair the appearance of the adherend. This has led to a demand for further improvements to create a more colorless and transparent adhesive composition.

The present invention aims to provide a moisture-curable adhesive composition that is colorless and highly transparent.

In order to obtain a moisture-curing adhesive with excellent colorless transparency that does not impair the appearance of the adherend after bonding, the inventors deliberately prepared a moisture-curing adhesive composition that did not contain chlorinated polyolefin resin. However, although the YI (yellowness index) of this adhesive composition was somewhat reduced, it still exhibited a slight yellowish tint. Furthermore, when an antioxidant commonly used in moisture-curing adhesive compositions was added to the composition, the YI value increased and the yellowish tint actually increased. Thus, even when components that may be involved in discoloration were removed from the moisture-curing adhesive composition, the composition did not achieve sufficient colorless transparency to avoid impairing the appearance of the adherend after bonding. Furthermore, it was confirmed that the addition of an antioxidant commonly used in moisture-curing adhesive compositions actually increased the yellowish tint. Therefore, it became clear that new improvements were needed.

The inventors therefore conducted further trial and error to solve the above-mentioned problems. They unexpectedly discovered that a moisture-curable adhesive composition containing a curable resin whose main chain is polyoxyalkylene and has a terminal hydrolyzable silyl group, a curable resin whose main chain is a vinyl copolymer and has an intramolecular hydrolyzable silyl group, a boron trifluoride complex, and a fluorescent brightener can be used as components to form a moisture-curable adhesive composition with excellent colorless transparency, leading to the completion of the present invention. The present invention employs the following configuration.

The first means of the present invention for solving the above problems is a moisture-curable adhesive composition comprising: (A) a curable resin having a polyoxyalkylene main chain at its terminal with a hydrolyzable silyl group represented by the following general formula (1); (B) a curable resin having a vinyl copolymer main chain with a hydrolyzable silyl group represented by the following general formula (1) in the molecule; (C) a boron trifluoride complex; and (D) a fluorescent brightening agent.
General formula (1); -SiR ¹ _a (OR ² ) _3-n
(wherein ^R1 represents an alkyl group having 1 to 10 carbon atoms, ^R2 represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2.

The second aspect of the present invention to solve the above problem is the moisture-curable adhesive composition described in the first aspect of the present invention, characterized in that component (A) has a urethane bond and/or a urea bond in the molecule.

The third aspect of the present invention to solve the above problems is the moisture-curable adhesive composition described in the first or second aspect of the present invention, characterized in that the cured product has excellent colorless transparency.

The present invention makes it possible to provide a new moisture-curing adhesive composition that exhibits excellent colorless transparency and does not impair the appearance of the adherend after adhesive curing. Furthermore, the present invention also facilitates color design of moisture-curing adhesive compositions, since the specific color of the coloring component does not change even when a coloring component is further blended.

The following describes in detail the modes for implementing the present invention. It should be noted that the present invention is not limited to these examples, and various modifications can be made without departing from the spirit of the present invention.

[Regarding the curable resin of component (A)]
The curable resin, which is component (A) in the moisture-curable adhesive composition of the present invention, has a polyoxyalkylene main chain and a hydrolyzable silyl group at its end, represented by the general formula (1): -SiR ¹ _a (OR ² ) _3-n (wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, R ² represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2).

The curable resin of component (A) can be any known curable resin that has a urethane bond and/or a urea bond in the molecule, a terminal hydrolyzable silyl group represented by general formula (1) (hereinafter simply referred to as "hydrolyzable silyl group"), and a polyoxyalkylene main chain. The curable resin of component (A) can be any known resin, including those described in Japanese Patent Publication Nos. 3317353, 3030020, 3343604, JP-A-2004-518801, JP-A-2004-536957, and JP-A-2005-501146.

The hydrolyzable silyl group possessed by the curable resin of component (A) is a functional group to which 1 to 3 alkoxy groups (OR ² ) that are hydrolyzable groups are bonded in addition to the bond on the silicon atom connected to the main chain. Here, the hydrolyzable group (OR ² ) is an alkoxy group having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms). The number of hydrolyzable groups (OR ² ) is preferably 3 (a=0) when it is desired to increase the curing rate, and preferably 2 (a=1) or 1 (a=2) when it is desired to impart flexibility to the cured product. The functional group R1 bonded to the remaining bond on the silicon atom represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms, particularly preferably 1 or 2 carbon atoms).
When multiple hydrolyzable silyl groups are present in the curable resin (A), the functional groups may be the same or different. Furthermore, the curable resin (A) may contain a urethane bond and/or a urea bond in the molecule. It is presumed that the presence of a urethane bond and/or a urea bond in the molecule allows the boron trifluoride complex (C), described later, to function effectively, thereby making it easier for the curable resin to exhibit its curing ability.

The molecular weight of the curable resin (component A) is not particularly limited, but a number-average molecular weight of 1,000 to 80,000 is preferred, 1,500 to 60,000 is more preferred, and 2,000 to 40,000 is particularly preferred. If the molecular weight is below 1,000, the crosslinking density may be too high, resulting in a brittle coating film (cured product). If the molecular weight exceeds 80,000, the viscosity may increase, reducing workability, requiring large amounts of solvent or plasticizer, and other formulation limitations may be imposed.

[Regarding the curable resin of component (B)]
The curable resin that is component (B) in the moisture-curable adhesive composition of the present invention has a main chain that is a vinyl copolymer and has at its end a hydrolyzable silyl group represented by the general formula (1): -SiR ¹ _a (OR ² ) _3-n (where R ¹ represents an alkyl group having 1 to 10 carbon atoms, R ² represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2). Any known curable resin can be used as long as it has such a hydrolyzable silyl group in its molecule and has a main chain that is a vinyl copolymer.

The curable resin, which is the component (B) used in the moisture-curable adhesive composition of the present invention, is a curable resin having a hydrolyzable silyl group in the molecule and having a vinyl copolymer main chain.
The hydrolyzable silyl group in the curable resin of component (B), like the hydrolyzable silyl group in the curable resin of component (A), is a functional group in which 1 to 3 alkoxy groups (OR ² ) are bonded to silicon atoms other than the bonds connected to the main chain. The hydrolyzable group (OR ² ) is an alkoxy group having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms). The number of hydrolyzable groups (OR ² ) is preferably 3 (a=0) when a high curing rate is desired, and 2 (a=1) or 1 (a=2) is preferred when flexibility is desired to be imparted to the cured product. The functional group R1 bonded to the remaining bond on the silicon atom represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms, particularly preferably 1 or 2 carbon atoms). When multiple hydrolyzable silyl groups are present in the curable resin of component (B), these functional groups may be the same or different.

The molecular weight of the curable resin (component (B)) is not particularly limited, but a number-average molecular weight of 1,000 to 80,000 is preferred, 1,500 to 60,000 is more preferred, and 2,000 to 40,000 is particularly preferred. If the molecular weight is below 1,000, the crosslinking density may be too high, resulting in a brittle coating film (cured product). If the molecular weight exceeds 80,000, the viscosity may increase, reducing workability, requiring large amounts of solvent or plasticizer, and other formulation limitations may be imposed.

The curable resin (B) can be synthesized. The curable resin (B) can be synthesized by any conventional method. For example, it can be obtained by copolymerizing a polymerizable vinyl compound (b1) having a hydrolyzable silyl group in its molecule with another polymerizable vinyl compound (b2). The copolymerization conditions are not particularly limited, and general radical polymerization, anionic polymerization, and cationic polymerization methods, as well as the polymerization conditions for these polymerization methods, can be applied. Furthermore, various organic solvents can be used as the reaction solvent during polymerization, or low- or high-molecular-weight curable or non-curable resins that are liquid at room temperature can be used. Among these, the most preferred method is to use the curable resin (A) as a solvent and copolymerize the polymerizable vinyl compound (b1) having a hydrolyzable silyl group in its molecule with the polymerizable vinyl compound (b2) in the curable resin (A). By carrying out a vinyl polymerization reaction in the curable resin (A), the mixed viscosity of the curable resin (A) and the curable resin (B) can be adjusted to a low level, and the reaction solvent removal step required in conventional solution polymerization is no longer necessary, making this an industrially very useful production method. The polymerizable vinyl compound (b1) and the polymerizable vinyl compound (b2) each having a hydrolyzable silyl group in their molecule may be selected appropriately to achieve the desired performance, and one type may be used alone or two or more types may be used in combination.

Examples of polymerizable vinyl compounds (b1) having a hydrolyzable silyl group in the molecule include, but are not limited to, vinyl methoxysilane, vinyl ethoxysilane, 3-(meth)acryloylpropyl trimethoxysilane, 3-(meth)acryloylpropylmethyl dimethoxysilane, 3-(meth)acryloylmethyl diethoxysilane, and p-styryltrimethoxysilane. Of these, 3-methacryloylpropyl trimethoxysilane and 3-methacryloylpropylmethyl dimethoxysilane are most preferred in terms of cost and ease of polymerization reaction.

The polymerizable vinyl compound (b2) is one or more polymerizable vinyl group-containing monomers selected from acrylic acid compounds, methacrylic acid compounds, acrylonitrile compounds, and styrene compounds. Hereinafter, acrylic acid and methacrylic acid will be referred to as (meth)acrylic acid, and acrylate and methacrylate will be referred to as (meth)acrylate. Specific examples of the polymerizable vinyl compound (b2) include (meth)acrylic acid, methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, N,N-dimethylacrylamide, N
, N-diethylacrylamide, N-isopropylacrylamide, morpholine acrylate, (meth)acrylonitrile, styrene, α-methylstyrene, etc., but are not limited to these.

The blending amount of the polymerizable vinyl compound (b1) having a hydrolyzable silyl group in the molecule is preferably 0.1 to 50 mass%, more preferably 0.5 to 30 mass%, and most preferably 1.0 to 15 mass%, of the total mass of all monomer components constituting the curable resin (B) (the mass of the polymerizable vinyl compound (b1) + the other polymerizable vinyl compound (b2)), and it is copolymerized with the other polymerizable vinyl compound (b2) in such blending amount.

When synthesizing the curable resin (B) by copolymerization, a conventional chain transfer agent can be used in addition to the constituent monomer components. Using a chain transfer agent not only controls the molecular weight of the curable resin (B), but also adjusts the viscosity of the curable resin (B). Examples of chain transfer agents include, but are not limited to, mercapto compounds such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and thiophenol; mercaptosilane compounds such as gamma-mercaptopropyltrimethoxysilane, gamma-mercaptopropylmethyldimethoxysilane, gamma-mercaptopropyltriethoxysilane, and gamma-mercaptopropylmethyldiethoxysilane; disulfide compounds such as dibutyl disulfide and gamma-trimethoxysilylpropyl disulfide; and aromatic hydrocarbon compounds such as benzene and toluene. Among these, n-dodecyl mercaptan and mercaptosilane compounds are preferred due to their low odor, and mercaptosilane compounds are even more preferred because they function as chain transfer agents while also introducing crosslinkable silicon groups into the molecule. The chain transfer agent is preferably used in an amount ranging from 0.1 to 35% by mass, more preferably from 1 to 25% by mass, and particularly preferably from 5 to 15% by mass, based on the total mass of all monomer components constituting the curable resin (component (B)).

Furthermore, when synthesizing the curable resin (component (B)) by copolymerization, a conventionally known initiator suitable for radical polymerization, anionic polymerization, or cationic polymerization can be used. For example, in the case of the commonly used radical polymerization method, the polymerization initiator is a radical initiator. Examples of radical initiators that can be used include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methyl-4-trimethoxysilylpentonitrile), 2,2'-azobis(2-methyl-4-methyldimethoxysilylpentonitrile), azo compounds such as VA-046B, VA-057, VA-061, VA-085, VA-086, VA-096, V-601, V-65, and VAm-110 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., and peroxides such as benzoyl peroxide, t-alkyl peroxy esters, acetyl peroxide, and diisopropyl peroxycarbonate. The initiator is preferably used in the range of 0.1 to 10% by mass, and particularly preferably 0.5 to 5% by mass, based on the total mass of all monomer components that make up the curable resin (component (B)).

The blending ratio (parts by mass) of the curable resin (A) and the curable resin (B) is preferably in the range of (A):(B) = 5:95 to 95:5, more preferably 20:80 to 90:10, particularly preferably 30:70 to 80:20, and most preferably 40:60 to 70:30. If the blending ratio (parts by mass) of the curable resin (B) is less than (A):(B) = 95:5, the effect of blending the curable resin (B) (the effect of improving various properties such as adhesion, heat resistance, oil resistance, and water resistance) may be diminished. If the blending ratio (parts by mass) of the curable resin (A):(B) is more than 5:95, the viscosity may become extremely high, resulting in reduced workability.

[Regarding the boron trifluoride complex as component (C)]
The boron trifluoride complex, which is component (C) used in the moisture-curable adhesive composition of the present invention, is a complex compound of boron trifluoride and a Lewis base, and is a catalyst compound for curing the curable resin (A) and the curable resin (B) by causing a condensation reaction of crosslinkable silicon groups contained in the curable resin (A) and the curable resin (B).

Specific examples of the boron trifluoride complex of component (C) include amine complexes, alcohol complexes, ether complexes, thiol complexes, sulfide complexes, carboxylic acid complexes, and water complexes of boron trifluoride. Among boron trifluoride complexes, alcohol complexes and amine complexes are preferred due to their ease of availability and ease of formulation, and amine complexes, which combine stability and catalytic activity, are particularly preferred.

Examples of amine compounds that can be used for the amine complex of boron trifluoride include ammonia, monoethylamine, triethylamine, piperidine, aniline, morpholine, cyclohexylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, guanidine, 2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethylpiperidine, N-methyl-3,3'-iminobis(propylamine), ethylenediamine, diethylenetriamine, triethylenediamine, pentaethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,4-diaminobutane, and 1,9-diaminononane. , ATU (3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane), CTU guanamine (3,9-bis[2-(3,5-diamino-2,4,6-triazaphenyl)ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane), dodecanoic acid dihydrazide, hexamethylenediamine, m-xylylenediamine, dianisidine, 4,4'-diamino-3,3'-diethyldiphenylmethane, diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, tolidine base, m-toluylenediamine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, m- compounds having multiple primary amino groups such as N-(3-aminopropyl)-1,3-propanediamine, bis(3-aminopropyl)ether, Jeffamine manufactured by Huntsman, piperazine, cis-2,6-dimethylpiperazine, cis-2,5-dimethylpiperazine, 2-methylpiperazine, N,N'-di-t-butylethylenediamine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, 1,3-di-(4-piperidyl)-propane, 4-aminopropylaniline, homopiperazine, N,N'-diphenyl Compounds having multiple secondary amino groups such as thiourea, N,N'-diethylthiourea, and N-methyl-1,3-propanediamine, as well as methylaminopropylamine, ethylaminopropylamine, ethylaminoethylamine, laurylaminopropylamine, 2-hydroxyethylaminopropylamine, 1-(2-aminoethyl)piperazine, N-aminopropylpiperazine, 3-aminopyrrolidine, 1-o-tolylbiguanide, 2-aminomethylpiperazine, N-aminopropylaniline, ethylamine, 2-hydroxyethylaminopropylamine, laurylaminopropylamine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, and compounds of the formula H ₂ N(C ₂ H ₄ NH) _n Compounds represented by the formula H(n≒5) (trade name: Polyate, Tosoh Corporation, Japan), N-alkylmorpholine, 1,8-diazabicyclo[5.4.0]undecene-7, 6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene-7, 1,5-diazabicyclo[4.3.0]nonene-5, 1,4-diazabicyclo[2.2.2]octane, pyridine, N-alkylpiperidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and other polycyclic tertiary amine compounds, as well as γ-aminopropyltriethoxysilane and γ-aminopropylmethylsilane. Examples of aminosilane compounds include, but are not limited to, diethoxysilane, 4-amino-3-dimethylbutyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane, N-3-[amino(dipropyleneoxy)]aminopropyltriethoxysilane, (aminoethylaminomethyl)phenethyltriethoxysilane, N-(6-aminohexyl)aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane, and N-(2-aminoethyl)-11-aminoundecyltriethoxysilane. Amine complexes of boron trifluoride are commercially available, and these can be used in the present invention. Commercially available products include Anchor 1040, Anchor 1115, Anchor 1170, Anchor 1222, and BAK1171 manufactured by Air Products Japan Co., Ltd.

The boron trifluoride complex of component (C) may be selected appropriately to achieve the desired curing rate, etc., and may be used alone or in combination with two or more types. The amount of boron trifluoride complex of component (C) is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5.0 parts by mass, and most preferably 0.1 to 2.0 parts by mass, per 100 parts by mass of the combined total of the curable resin of component (A) and the curable resin of component (B). If the amount of boron trifluoride complex of component (C) is less than 0.01 part by mass, the curing acceleration effect may be insufficient, while if it exceeds 10 parts by mass, problems such as poor storage stability of the moisture-curable adhesive composition may occur.

[Regarding the fluorescent whitening agent (D)]
The "fluorescent brightening agent" as component (D) used in the moisture-curable adhesive composition according to the present invention is a component that, when used together with components (A) to (C), makes the moisture-curable adhesive composition according to the present invention colorless and transparent.

The fluorescent brightening agent (component (D)) may be a coumarin derivative, a benzoxazole derivative, a naphthalene derivative, a pyrarizone derivative, a benzidine derivative, a stilbene derivative, or the like. These may be selected appropriately and may be used alone or in combination of two or more.

Specific examples of the above-mentioned fluorescent brightening agents include, for example, Tinopal OB (BASF, Germany) as a benzoxazole/thiophene derivative, Kaylight® B (Nippon Kayaku Co., Ltd., Japan) as a coumarin derivative, Kaylight OSN (Nippon Kayaku Co., Ltd., Japan) and Kaylight OS (Nippon Kayaku Co., Ltd., Japan) as benzoxazole derivatives, Kaylight KB (Nippon Kayaku Co., Ltd., Japan) and NIKKAFLUOR KB (Nippon Chemical Industry Co., Ltd., Japan) as benzoxazole/naphthalene derivatives, and NIKKAFLUOR 2R conc. (Nippon Chemical Industry Co., Ltd., Japan) and Whitefluor® PSN conc. (Sumitomo Chemical Co., Ltd., Japan) as benzoxazole/stilbene derivatives. (Nippon Chemical Industry Co., Ltd., Japan) etc. can be used.

The amount of fluorescent brightening agent (component (D)) blended is not particularly limited, but is preferably 0.0002 to 1 part by mass, and more preferably 0.002 to 0.2 parts by mass, per 100 parts by mass of the combined total of the curable resin (component (A)) and the curable resin (component (B)), so that the moisture-curable adhesive composition according to the present invention is colorless and transparent. If the amount of fluorescent brightening agent (component (D)) is less than 0.0002 parts by mass, the effect of eliminating the yellowness may not be sufficient, and if it exceeds 1 part by mass, problems such as the adhesive composition becoming discolored may occur.

[Other ingredients]
The moisture-curable adhesive composition according to the present invention may contain any conventionally known compound or substance as other components, provided that the effects of the present invention are not impaired. For example, various resins other than the curable resin (A) used in the present invention (e.g., epoxy resins, acrylic resins, etc.), curing catalysts other than the boron trifluoride complex (C), adhesion-imparting components (e.g., silane coupling agents such as aminosilane compounds, epoxysilane compounds, mercaptosilane compounds, (meth)acrylicsilane compounds, isocyanatesilane compounds, and vinylsilane compounds, tackifying resins such as styrene resins, chlorinated polyolefin resins, etc.), hydrophilic or hydrophobic silica-based powders, acrylic resin powders, fillers such as calcium carbonate, thixotropic agents such as amide wax, dehydrating agents such as calcium oxide, diluents, plasticizers, flame retardants, oligomers, antioxidants, pigments, drying oils, etc. may be blended.

Specifically, a diluent can be blended into the moisture-curable adhesive composition of the present invention, provided that the effects of the present invention are not impaired. Commercially available diluents may be used, such as dipropylene glycol dimethyl ether (e.g., Proglide® DMM (BASF, Germany)).

The moisture-curable adhesive composition of the present invention can contain an aminosilane, provided that the effects of the present invention are not impaired. Commercially available aminosilanes may be used, such as KBM-903 (Shin-Etsu Chemical Co., Ltd., Japan).

The moisture-curable adhesive composition of the present invention can be blended with an antioxidant, provided that the effects of the present invention are not impaired. Commercially available antioxidants may be used, such as Irganox® 1010 (BASF, Germany) and Tinuvin® 770DF (BASF, Germany).

The moisture-curable adhesive composition of the present invention can be blended with components capable of imparting color to the moisture-curable adhesive composition, as long as the effects of the present invention are not impaired. For example, heavy calcium carbonate NS#400 (Nitto Funka Kogyo Co., Ltd., Japan) or heavy calcium carbonate Nanox #30 (Maruo Calcium Co., Ltd., Japan) can be blended to impart a white hue to the moisture-curable adhesive composition, and toner NV7-224 (Nippon Pigment Co., Ltd.) can be blended to impart a black hue to the moisture-curable adhesive composition.

The moisture-curable adhesive composition of the present invention may contain a thixotropic agent, provided that the effect of the present invention is not impaired. For example, Disparlon (registered trademark) 6650 (Kusumoto Chemicals Co., Ltd., Japan) may be added.

The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

1. Reagents and Substrates

For the various tests shown below, the following reagents were used: Tinopal OB (BASF, Germany), Kayalight B (Nippon Kayaku Co., Ltd., Japan), Kayalight OSN (Nippon Kayaku Co., Ltd., Japan), Kayalight OS (Nippon Kayaku Co., Ltd., Japan), Kayalight KB (Nippon Kayaku Co., Ltd., Japan), NIKKAFLUOR KB (Nippon Chemical Industry Co., Ltd., Japan), NIKKAFLUOR 2R conc. (Nippon Chemical Industry Co., Ltd., Japan), Whitefluor PSN conc. (Sumitomo Chemical Co., Ltd., Japan), and NIKKAFLUOR RP conc. (Nippon Chemical Industry Co., Ltd., Japan), Oil Blue 2N (Orient Chemical Co., Ltd., Japan), Proglide DMM (BASF, Germany), KBM-903 (Shin-Etsu Chemical Co., Ltd., Japan), Irganox 1010 (BASF, Germany), Tinuvin 770DF (BASF, Germany), boron trifluoride monoethylamine (Stella Chemifa Co., Ltd., Japan), heavy calcium carbonate NS#400 (Nitto Funka Kogyo Co., Ltd., Japan), heavy calcium carbonate Nanox #30 (Maruo Calcium Co., Ltd., Japan), toner NV7-224 (Nippon Pigment Co., Ltd., Japan), and Disparlon 6650 (Kusumoto Chemical Co., Ltd., Japan) were used.

2. Preparation of adhesive composition

A liquid mixture of a curable resin of component (A) (i.e., a curable resin whose main chain is polyoxyalkylene and whose terminal has a hydrolyzable silyl group represented by general formula (1): -SiR ¹ _a (OR ² ) _3-n (wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, R ² represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2)) and a curable resin of component (B) (i.e., a curable resin whose main chain is a vinyl copolymer and whose molecule has a hydrolyzable silyl group represented by general formula (1): -SiR ¹ _a (OR ² ) _3-n (wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, R ² represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2)) was prepared.

[Preparation of Curable Resin (A)]
In a reaction vessel, 206.4 parts by mass of N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane was stirred under a nitrogen atmosphere at room temperature, while 172.2 parts by mass of methyl acrylate (2 molar equivalents relative to the N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane) was added dropwise over 1 hour, and the mixture was allowed to react at 50°C for 7 days, thereby obtaining a silane compound (SE-1) having a methyldimethoxysilyl group and a secondary amino group in the molecule.

In a separate reaction vessel, 100 parts by mass of PMLS4012 (manufactured by Asahi Glass Co., Ltd., product name: polyoxypropylene polyol, number average molecular weight 10,000), 4.83 parts by mass of isophorone diisocyanate, and a trace amount of Nikka Octix Zirconium (manufactured by Nippon Chemical Industry Co., Ltd., product name: 2-ethylhexanoate zirconyl compound solution (Zr content = approximately 12% by mass), 20 ppm zirconium metal equivalent relative to PMLS4012) were charged and reacted at 80°C for 3 hours while stirring and mixing under a nitrogen atmosphere, yielding a urethane-based resin (U-1) whose main chain is an oxyalkylene polymer and whose molecule contains isocyanate groups.

8.39 parts by mass of the silane compound (SE-1) was added to the urethane resin (U-1), and while stirring and mixing under a nitrogen atmosphere, the isocyanate groups in the urethane resin (U-1) and the secondary amino groups in the silane compound (SE-1) were reacted at 80°C for 1 hour to obtain a curable resin of component (A) whose main chain is an oxyalkylene polymer and whose molecule contains a urethane group, a urea group substituted with one active hydrogen, and a methyldimethoxysilyl group. After completion of the reaction, IR measurement was performed, and the characteristic absorption (2265 cm ^-1 ) assigned to the isocyanate group was not observed.

[Preparation of a liquid mixture of the curable resin (A) and the curable resin (B)]
A reaction vessel was charged with 100 parts by mass of the curable resin (A) and heated to 80°C under a nitrogen atmosphere. A monomer mixture containing 37.5 parts by mass of methyl methacrylate, 25 parts by mass of lauryl methacrylate, 3.0 parts by mass of 3-acryloxypropyltrimethoxysilane, 7.0 parts by mass of 3-mercaptopropyltrimethoxysilane, and 0.50 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) was added dropwise over 30 minutes to carry out a polymerization reaction. After further reaction at 80°C for 30 minutes, a mixed solution of 0.200 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) and 10 parts by mass of methyl ethyl ketone was added dropwise to carry out a polymerization reaction. Next, after reacting for 30 minutes at 80°C, a mixed solution of 0.10 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) and 10 parts by mass of methyl ethyl ketone was added dropwise to carry out a polymerization reaction. After further reacting for 3 hours at 80°C, the methyl ethyl ketone was distilled off under reduced pressure to obtain a liquid mixture of the curable resin of component (A) and the curable resin of component (B) having a trimethoxysilyl group in the molecule. This liquid mixture had a mass ratio of curable resin of component (A):curable resin of component (B) = 58:42.

Furthermore, the moisture-curable adhesive composition of the present invention and a comparative moisture-curable adhesive composition are each prepared using the procedures described below.

The blending ratios of each raw material in the moisture-curing adhesive compositions of each example and comparative example are summarized in Tables 1-1 to 1-6.

<Procedure for preparing transparent moisture-curable adhesive composition>
The curable resin and fluorescent agent were placed in a sealed reaction vessel (planetary mixer) equipped with a stirrer in the proportions (parts by mass) shown in Tables 1-1 to 1-4 and kneaded for 10 minutes at room temperature and normal pressure. The mixture was then stirred and mixed for 1 hour under a reduced pressure of 60 mmHg or less while heating at 100 to 120°C. The mixture was then cooled and stirred for another hour. After depressurizing with nitrogen, the resulting paste-like slurry was added with a solution of the diluent Proglide DMM, the silane coupling agent KBM-903, the boron trifluoride complex boron trifluoride monoethylamine, and the antioxidant, and kneaded under sealed conditions that were protected from moisture to obtain a moisture-curable adhesive composition. The resulting moisture-curable adhesive composition was then filled into a sealed container that was protected from moisture.

<Procedure for preparing white moisture-curable adhesive composition>
The curable resin, fluorescent agent, and filler heavy calcium carbonate NS#400 and Nanox#30 were added to a sealed reaction vessel (planetary mixer) equipped with a stirrer in the proportions (parts by mass) shown in Table 1-5. The mixture was mixed at room temperature and normal pressure for 10 minutes, and then kneaded for 30 minutes under a reduced pressure of 60 mmHg or less. The mixture was then stirred and mixed for 1 hour while heated to 100-120°C under a reduced pressure of 60 mmHg or less. The mixture was cooled and further stirred and mixed for 1 hour. After depressurizing with nitrogen, the resulting paste-like slurry was added to a solution containing the diluent Proglide DMM, the silane coupling agent KBM-903, the boron trifluoride complex boron trifluoride monoethylamine, and the thixotropic agent. The mixture was then kneaded under sealed conditions in a moisture-proof enclosure to obtain a moisture-curable adhesive composition. The resulting moisture-curable adhesive composition was then filled into a moisture-proof sealed container.

<Procedure for preparing black moisture-curable adhesive composition>
The curable resin, fluorescent agent, filler heavy calcium carbonate NS#400, Nanox #30, and toner NV7-224 were mixed in the proportions (parts by mass) shown in Table 1-6 into a sealed reaction vessel (planetary mixer) equipped with a stirrer, kneaded at room temperature and pressure for 10 minutes, and then kneaded for 30 minutes under a reduced pressure of 60 mmHg or less. The mixture was then stirred and mixed for 1 hour while heated to 100-120°C under a reduced pressure of 60 mmHg or less. The mixture was cooled and further stirred and mixed for 1 hour. After depressurizing with nitrogen, the resulting paste-like slurry was added with a solution of the diluent Proglide DMM, the silane coupling agent KBM-903, the boron trifluoride complex boron trifluoride monoethylamine, and the thixotropic agent, and kneaded under sealed conditions that were sealed and protected from moisture, to obtain a moisture-curable adhesive composition. The resulting moisture-curable adhesive composition was filled into a sealed container that was protected from moisture.

A moisture-curable adhesive composition for each example was prepared.

[Preparation of Moisture-Curable Adhesive Composition (Example 1-1)]
100 parts by weight of a liquid mixture of the curable resin (A) and the curable resin (B), and 0.02 parts by weight of Tinopal OB, a fluorescent brightening agent (D), were added to a sealed reaction vessel (planetary mixer) equipped with a stirrer and kneaded at room temperature and normal pressure for 10 minutes. The mixture was then stirred and mixed for 1 hour under a reduced pressure of 60 mmHg or less while heated to 100-120 °C. The mixture was cooled and further stirred and mixed for 1 hour. After depressurizing with nitrogen, the resulting paste-like slurry was added with 5 parts by weight of the diluent Proglide DMM, 5 parts by weight of the aminosilane silane coupling agent KBM-903, and 0.1 parts by weight of the boron trifluoride complex boron trifluoride monoethylamine (C), and kneaded under sealed conditions that blocked moisture to obtain the moisture-curable adhesive composition of Example 1-1. The resulting moisture-curable adhesive composition was filled in a sealed container that was moisture-proof, and stored until it was used in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 1-2)]
The moisture-curable adhesive composition of Example 1-2 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 0.5 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 2-1)]
A moisture-curable adhesive composition of Example 2-1 was obtained in the same manner as in Example 1-1, except that the amount of Kayalight B, the fluorescent brightening agent of component (D), was changed to 0.02 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 3-1)]
The moisture-curable adhesive composition of Example 3-1 was obtained in the same manner as in Example 1-1, except that the amount of Kayalight OSN, the fluorescent brightening agent of component (D), was changed to 0.02 parts by mass. The composition was then filled into an airtight container that was moisture-proof, and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 4-1)]
The moisture-curable adhesive composition of Example 4-1 was obtained in the same manner as in Example 1-1, except that the amount of Kayalight OS, the fluorescent brightening agent of component (D), was changed to 0.02 parts by mass. The composition was then filled into an airtight container that was moisture-proof, and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 5-1)]
A moisture-curable adhesive composition of Example 5-1 was obtained in the same manner as in Example 1-1, except that the amount of NIKKAFLUOR KB, the fluorescent brightening agent of component (D), was changed to 0.02 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 6-1)]
The moisture-curable adhesive composition of Example 6-1 was obtained in the same manner as in Example 1-1, except that the amount of NIKKAFLUOR RP conc., the fluorescent brightening agent of component (D), was changed to 0.02 parts by mass. The composition was then filled into a sealed container that was moisture-proof and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 7-1)]
A moisture-curable adhesive composition of Example 7-1 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 0.002 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 7-2)]
A moisture-curable adhesive composition of Example 7-2 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 0.005 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 7-3)]
The moisture-curable adhesive composition of Example 7-3 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 0.008 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 7-4)]
The moisture-curable adhesive composition of Example 7-4 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 0.01 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 7-5)]
The moisture-curable adhesive composition of Example 7-5 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 0.02 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Examples 7-6)]
The moisture-curable adhesive composition of Example 7-6 was obtained in the same manner as in Example 1-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 1 part by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 8-1)]
A moisture-curable adhesive composition of Example 8-1 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of Kayalight B. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 8-2)]
A moisture-curable adhesive composition of Example 8-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.005 parts by mass of Kayalight B. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 8-3)]
A moisture-curable adhesive composition of Example 8-3 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.01 parts by mass of Kayalight B. The composition was then filled into an airtight container that was moisture-proof and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 9-1)]
The moisture-curable adhesive composition of Example 9-1 was obtained by mixing them in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of Kayalight OSN. This composition was then filled into an airtight container that was protected from moisture and stored until it was used in each test.

[Preparation of moisture-curable adhesive composition (Example 9-2)]
A moisture-curable adhesive composition of Example 9-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.01 parts by mass of Kayalight OSN. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 10-1)]
A moisture-curable adhesive composition of Example 10-1 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of Kayalight OS. The composition was then filled into an airtight container that was moisture-proof, and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 10-2)]
A moisture-curable adhesive composition of Example 10-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.01 parts by mass of Kayalight OS. The composition was then filled into an airtight container that was moisture-proof, and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 11-1)]
A moisture-curable adhesive composition of Example 11-1 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of NIKKAFLUOR KB. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 11-2)]
A moisture-curable adhesive composition of Example 11-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.01 parts by mass of NIKKAFLUOR KB. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 12-1)]
A moisture-curable adhesive composition of Example 12-1 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of NIKKAFLUOR 2R conc., and the composition was filled into a sealed container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 12-2)]
A moisture-curable adhesive composition of Example 12-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent of component D) was 0.01 parts by mass of NIKKAFLUOR 2R conc., and the composition was filled into a sealed container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Example 13-1)]
The moisture-curable adhesive composition of Example 13-1 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of Whitefluor PSN conc. The composition was filled into a sealed container that was moisture-proof, and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 13-2)]
The moisture-curable adhesive composition of Example 13-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.01 parts by mass of Whitefluor PSN conc. The composition was filled into a sealed container that was moisture-proof, and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 14-1)]
A moisture-curable adhesive composition of Example 14-1 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.002 parts by mass of NIKKAFLUOR RP conc. The composition was filled into a sealed container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 14-2)]
A moisture-curable adhesive composition of Example 14-2 was obtained in the same manner as in Example 1-1, except that the fluorescent brightening agent (D) was 0.01 parts by mass of NIKKAFLUOR RP conc. The composition was filled into a sealed container that was protected from moisture and stored until use in each test.

A comparative moisture-curing adhesive composition was prepared.

[Preparation of Moisture-Curable Adhesive Composition (Comparative Example 1-1)]
A moisture-curable adhesive composition of Comparative Example 1-1 was obtained in the same manner as in Example 1-1, except that Tinopal OB, the fluorescent brightening agent of component (D), was not blended. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of Moisture-Curable Adhesive Composition (Comparative Example 1-2)]
A moisture-curable adhesive composition of Comparative Example 1-2 was obtained in the same manner as in Example 7-1, except that Tinopal OB, the fluorescent brightening agent of component (D), was not blended. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

Furthermore, a white moisture-curable adhesive composition was prepared.

[Preparation of moisture-curable adhesive composition (Example 15-1)]
100 parts by mass of a liquid mixture of the curable resin (A) and the curable resin (B), 0.02 parts by mass of Tinopal OB, a fluorescent brightening agent (D), 16 parts by mass of heavy calcium carbonate NS#400, and 16 parts by mass of Nanox #30 were placed in a sealed reaction vessel (planetary mixer) equipped with a stirrer, kneaded for 10 minutes at room temperature and atmospheric pressure, and then kneaded for 30 minutes under a reduced pressure of 60 mmHg or less. Thereafter, the mixture was stirred and mixed for 1 hour while heating at 100 to 120°C under a reduced pressure of 60 mmHg or less. The mixture was further stirred and mixed for 1 hour while cooling, and after depressurizing with nitrogen, a solution prepared by dissolving 5 parts by mass of Proglide DMM as a diluent, 5 parts by mass of KBM-903 as a silane coupling agent, and 0.1 parts by mass of boron trifluoride monoethylamine as a boron trifluoride complex (component (C))) was added to the resulting paste-like slurry, and the mixture was kneaded under sealed conditions that blocked out moisture to obtain a moisture-curable adhesive composition, which was then filled into a sealed container that blocked out moisture.

[Preparation of moisture-curable adhesive composition (Example 15-2)]
The moisture-curable adhesive composition of Example 15-2 was obtained in the same manner as in Example 15-1, except that the amount of Tinopal OB, the fluorescent brightening agent of component (D), was changed to 1.5 parts by mass. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-3)]
The moisture-curable adhesive composition of Example 15-3 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of Kayalight B. The composition was then filled into an airtight container that was moisture-proof and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-4)]
The moisture-curable adhesive composition of Example 15-4 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of Kayalight OSN. The composition was then filled into a sealed container that was moisture-proof and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-5)]
The moisture-curable adhesive composition of Example 15-5 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of Kayalight OS. The composition was then filled into an airtight container that was moisture-proof and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-6)]
The moisture-curable adhesive composition of Example 15-6 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of NIKKAFLUOR KB. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-7)]
The moisture-curable adhesive composition of Example 15-7 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of NIKKAFLUOR 2R conc. The composition was filled into a sealed container that was moisture-proof, and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-8)]
The moisture-curable adhesive composition of Example 15-8 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of Whitefluor PSN conc. The composition was filled into a sealed container that was moisture-proof, and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 15-9)]
The moisture-curable adhesive composition of Example 15-9 was obtained in the same manner as in Example 15-1, except that the fluorescent brightening agent (D) was 0.02 parts by mass of NIKKAFLUOR RP conc. The composition was filled into a sealed container that was moisture-proof, and stored until use in each test.

In addition, a black moisture-curable adhesive composition was prepared.

[Preparation of moisture-curable adhesive composition (Example 16-1)]
A moisture-curable adhesive composition of Example 16-1 was obtained in the same manner as in Example 15-1, except that 3 parts by mass of toner NV7-224 was added, and the composition was filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 16-2)]
A moisture-curable adhesive composition of Example 16-2 was obtained in the same manner as in Example 15-2, except that 3 parts by mass of toner NV7-224 was added, and the composition was filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 16-3)]
A moisture-curable adhesive composition of Example 16-3 was obtained in the same manner as in Example 15-3, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 16-4)]
A moisture-curable adhesive composition of Example 16-4 was obtained in the same manner as in Example 15-4, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until use in each test.

[Preparation of moisture-curable adhesive composition (Example 16-5)]
A moisture-curable adhesive composition of Example 16-5 was obtained in the same manner as in Example 15-5, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until it was used in each test.

[Preparation of moisture-curable adhesive composition (Example 16-6)]
The moisture-curable adhesive composition of Example 16-6 was obtained in the same manner as in Example 15-6, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until it was used in each test.

[Preparation of Moisture-Curable Adhesive Composition (Examples 16-7)]
A moisture-curable adhesive composition of Example 16-7 was obtained in the same manner as in Example 15-7, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until it was used in each test.

[Preparation of moisture-curable adhesive composition (Example 16-8)]
The moisture-curable adhesive composition of Example 16-8 was obtained in the same manner as in Example 15-8, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until it was used in each test.

[Preparation of moisture-curable adhesive composition (Example 16-9)]
The moisture-curable adhesive composition of Example 16-9 was obtained in the same manner as in Example 15-9, except that 3 parts by mass of toner NV7-224 was blended. The composition was then filled into an airtight container that was protected from moisture and stored until it was used in each test.

3. Evaluation testing of moisture-curing adhesive compositions

[Procedure for evaluating color difference and turbidity of moisture-curable adhesive compositions]

Using the moisture-curable adhesive compositions of each example and comparative example, tests were conducted to confirm and evaluate the color difference and turbidity of the cured film formed by curing each moisture-curable adhesive composition.

The moisture-curable adhesive composition of each Example and Comparative Example was poured into a circular container having a diameter of 50 mm and a thickness of 2 mm, and cured for 7 days in an atmosphere of 23±2°C and a relative humidity of 50±5% to form a cured film having a thickness of 2 mm. The YI value and haze (turbidity) value of the cured film were measured using a COH400 simultaneous color and turbidity analyzer (Nippon Denshoku Industries Co., Ltd., Japan), and the values were recorded.
Here, the color difference of the cured film was calculated from the measured values of X, Y, and Z of the cured film using the formula YI = 100 (1.28X - 1.06Z)/Y. A value greater than +2 indicates a yellowish appearance, a value below -2 indicates a white to blue appearance, a value below ±2 indicates an appearance that is close to colorless, and the smaller the value and the closer it is to 0, the more the film is perceived as being virtually colorless.
Furthermore, when the measured turbidity (%) of the cured film is 30 or less, it is judged to have sufficient transparency for practical use.

[Procedure for checking viscosity of moisture-curing adhesive compositions]

A viscosity test was conducted using the moisture-curable adhesive compositions of each example and comparative example.

Each moisture-curing adhesive composition was placed in a 50cc plastic container, and the viscosity was measured using a viscometer TVB-15H (Toki Sangyo Co., Ltd., Japan) at 23°C after 10 rotations. The viscosity when using Tinopal OB was set to 1, and the viscosity under various conditions was expressed as a ratio, and each value was recorded.

[Procedure for verifying tensile shear bond strength of moisture-curable adhesive compositions]

Tests were conducted to confirm the tensile shear adhesive strength using the moisture-curable adhesive compositions of each example and comparative example.

Each moisture-curing adhesive composition was applied to an acrylic plate (length: 100 mm, width: 25 mm, thickness: 3 mm) whose surface had been degreased with ethanol. The plates were then bonded together with 0.2 mm diameter glass beads as spacers, with an overlap length of 12.5 mm ± 0.25 mm, to ensure a consistent adhesive thickness. The plates were then cured for 7 days at 23 ± 2°C and 50 ± 5% relative humidity to obtain test specimens. The tensile shear bond strength of each test specimen was then measured. Tensilon universal testing machine (A&D Co., Ltd., Japan) was used to measure the tensile shear bond strength in accordance with JIS K 6850, at a tensile speed of 5 mm/min, and the measured values were recorded.

4. About the results

[Evaluation results of moisture-curable adhesive compositions based on turbidity and color difference]
The moisture-curable adhesive compositions of each Example and Comparative Example were used to evaluate color difference and turbidity, and the results are shown in Tables 2-1 to 2-4.

A color difference test for moisture-curable adhesive compositions was conducted to confirm the color difference using the moisture-curable adhesive compositions of each Example and Comparative Example, and the color difference was recorded.

As a result, the color difference for the moisture-curing adhesive composition of Comparative Example 1-1 was 1.98, which is within the range where it is visually perceived as approaching yellow to colorless, but it cannot be said to be excellent in the degree of colorlessness that is desired, where the color is visually perceived as colorless with virtually no noticeable coloration. Furthermore, the color difference for the moisture-curing adhesive composition of Comparative Example 1-2, in which an antioxidant was added to Comparative Example 1-1, was 2.12, confirming that it was visually perceived as having a slight yellowish tinge (Table 2-1).

On the other hand, the color differences for the moisture-curable adhesive compositions of Examples 1-1 to 14-2 were -0.19, 0.12, 0.20, 0.58, 0.56, -0.33, 0.81, 0.68, 0.48, 0.32, 0.35, -0.12, -0.35, 0.54, 0.50, 0.45, 0.77, 0.54, 1.02, 0.55, 0.89, 0.75, 1.11, 0.78, 0.75, 0.68, 1.20, and 0.79, respectively, which were significantly smaller than those of the comparative examples. It was revealed that a moisture-curable adhesive composition was obtained that was so excellent in the degree of colorlessness that it was visually perceived as being colorless with virtually no noticeable coloration, and was judged to be substantially colorless.Furthermore, it was revealed that even when an antioxidant, which was shown in the comparative examples to be a component that causes a yellowish tinge when added, was added to a moisture-curable adhesive composition containing components (A) to (D), a moisture-curable adhesive composition was obtained that was so excellent in the degree of colorlessness that it was visually perceived as being colorless with virtually no noticeable coloration, and was judged to be substantially colorless. (Tables 2-1 to 2-4)

Next, a turbidity test for the moisture-curable adhesive composition was conducted to confirm the turbidity of the moisture-curable adhesive compositions of each Example and Comparative Example, and the turbidity was recorded.

As a result, the turbidity of the moisture-curing adhesive compositions of Comparative Example 1-1 and Comparative Example 1-2 was 2.01 and 4.11, respectively, confirming that the compositions had high transparency (Table 2-1 and Table 2-2). Furthermore, the turbidity of the moisture-curing adhesive compositions of Examples 1-1 to 6-1 was 1.65, 2.13, 1.84, 4.59, 2.16, 2.54, and 3.91, respectively, confirming that the compositions had high transparency (Table 2-1). Furthermore, the turbidity of the moisture-curable adhesive compositions of Examples 7-1 to 14-2, to which an antioxidant was added, was 3.89, 4.05, 3.99, 4.02, 4.13, 5.12, 3.77, 4.01, 4.03, 3.55, 3.98, 4.01, 4.13, 3.55, 3.98, 4.01, 4.13, 3.87, 3.56, 5.12, 6.35, 3.68, 3.98, 5.23, and 6.89, respectively, confirming that regardless of the concentration or fluorescent brightener used, a product possessing high transparency characteristics was obtained (Tables 2-2 to 2-4).

It has been revealed that the moisture-curable adhesive composition of the present invention exhibits the excellent property of being colorless and transparent. Furthermore, it has been revealed that the range of types and amounts of fluorescent brighteners that can be used in the colorless and transparent moisture-curable adhesive composition of the present invention is extremely broad, making it highly versatile.

And because it is colorless and transparent, it is understood that the color will not change even if the moisture-curable adhesive composition of the present invention is colored with a pigment or the like. Therefore, when the colors of the moisture-curable adhesive compositions of Examples 15-1 to 16-9, which are colored moisture-curable adhesive compositions of the present invention, were checked, it was confirmed that the color was consistent with the original color design.

[Confirmation of viscosity change, adhesion, and curing properties of moisture-curable adhesive composition]
The viscosity of the moisture-curable adhesive compositions of the above-mentioned Examples and Comparative Examples was confirmed, and the results are shown in Tables 2-1 to 2-4.

When the initial viscosity of the moisture-curing adhesive compositions of each Example and Comparative Example at the time of production was confirmed, it was confirmed that the viscosity under various conditions, with a ratio of 0.98 to 1.11, when the viscosity when using Tinopal OB was set to 1, showed almost no change (Tables 2-1 to 2-4). Furthermore, the storage stability of each of the moisture-curing adhesive compositions was confirmed when they were kept in an accelerated environment at 50°C for two weeks, and the viscosity ranged from 0.98 to 1.19, showing almost no change in viscosity. Furthermore, it was confirmed that the adhesion and curing properties of each of the moisture-curing adhesive compositions were both good.

[Confirmation of tensile shear adhesive strength of moisture-curable adhesive composition]
The tensile shear adhesive strength of the moisture-curable adhesive compositions of the above-mentioned Examples and Comparative Examples was confirmed, and the results are shown in Tables 2-1 to 2-4.

The tensile shear adhesive strength of each moisture-curing adhesive composition was confirmed to be good values, ranging from 1.09 to 1.46 N·mm ² for each example and from 1.17 to 1.32 N·mm ² for each comparative example (Tables 2-1 to 2-4).

[Confirming the luminescence of moisture-curing adhesive compositions]

Furthermore, we confirmed whether the cured film of the colorless and transparent moisture-curable adhesive composition of the above example was capable of visibly emitting light when irradiated with UV light in the A range.

Each of the moisture-curing adhesive compositions described above was poured into a circular container with a diameter of 50 mm and a thickness of 2 mm to create a cured film (2 mm thick). The cured film was then irradiated with UV-A light (using a 4 W black light, fluorescent wavelength: 365 nm, Ohm Electric Co., Ltd., Japan) at a distance of 10 cm in a 23°C atmosphere, and the state of light emission was confirmed visually. As a result, it was confirmed that the cured film made using the colorless and transparent moisture-curing adhesive composition of each Example, which is the moisture-curing adhesive composition of the present invention, emitted visible light when irradiated with UV-A light, making it possible to identify the presence of the cured film by its light emission. On the other hand, the cured film made using the moisture-curing adhesive composition of the Comparative Example did not emit visible light even when irradiated with UV-A light.

According to the present invention, a moisture-curable adhesive composition is prepared by mixing a curable resin (A) having a polyoxyalkylene main chain and a hydrolyzable silyl group at its terminal represented by the general formula (1): -SiR ¹ _a (OR ² ) _3-n (wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, R ² represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2), and a curable resin (B) having a vinyl copolymer main chain and a vinyl copolymer main chain and a hydrolyzable silyl group at its terminal represented by the general formula (1): -SiR ¹ _a (OR ² ) _3-n (wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, R ⁽² ) represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2.) a boron trifluoride complex as component (C) and a fluorescent brightening agent as component (D), it has become possible to provide a new moisture-curable adhesive composition that is extremely colorless and transparent, does not change color when colored, and has good viscosity and adhesive strength.

Claims (2)

The composition contains: (A) a curable resin having a polyoxyalkylene main chain at its terminal with a hydrolyzable silyl group represented by the following general formula (1); (B) a curable resin having a vinyl copolymer main chain at its terminal with a hydrolyzable silyl group represented by the following general formula (1); (C) a boron trifluoride complex; and (D) a fluorescent brightening agent ;
A moisture-curable adhesive composition characterized in that component (A) has a urethane bond and/or a urea bond in the molecule .
General formula (1); -SiR ¹ _a (OR ² ) _3-a
(wherein ^R1 represents an alkyl group having 1 to 10 carbon atoms, ^R2 represents an alkyl group having 1 to 6 carbon atoms, and a is 0, 1, or 2.) The moisture-curable adhesive composition according to claim 1, characterized in that the color difference (YI value) of the cured product is -0.35 or more and 1.20 or less.