JP6780939B2 - Impact-resistant adhesives and aircraft adhesives - Google Patents

Description

The present invention relates to an impact-resistant adhesive having excellent adhesiveness and impact resistance, and an aircraft adhesive comprising the impact-resistant adhesive.

(Meta) acrylic adhesives containing a (meth) acrylic adhesive component and epoxy adhesives containing an epoxy adhesive component are used in various fields as typical adhesives. In particular, (meth) acrylic adhesives and epoxy adhesives are indispensable for adhering structural materials such as vehicles such as automobiles and buildings.

In recent years, adhesives have come to be used for adhering structural materials such as aircraft for the purpose of weight reduction and the like. However, aircraft adhesives are required to have impact resistance in the harsh environment of severe cold at high altitudes, which is unthinkable in ordinary applications.
As an adhesive having excellent impact resistance, it is known that a rubber component such as an elastomer is blended in the adhesive. However, it has been suggested that the adhesive containing the rubber component improves the impact resistance but lowers the adhesiveness (for example, Patent Document 1). Therefore, an adhesive having excellent adhesiveness and impact resistance has been required.

Japanese Unexamined Patent Publication No. 2004-515565

In view of the above situation, an object of the present invention is to provide an impact-resistant adhesive having excellent adhesiveness and impact resistance, and an aircraft adhesive made of the impact-resistant adhesive.

The present invention is an impact resistant adhesive containing a (meth) acrylic adhesive component or an epoxy adhesive component and a modified polyvinyl acetal having an imine structure.
The present invention will be described in detail below.

As a result of diligent studies, the present inventors have added a modified polyvinyl acetal having an imine structure to the (meth) acrylic adhesive component or the epoxy adhesive component in a harsh environment without impairing the adhesiveness. The present invention has been completed by finding that it can exhibit high impact resistance even underneath.

The impact-resistant adhesive of the present invention (hereinafter, also simply referred to as “adhesive”) contains a (meth) acrylic adhesive component or an epoxy adhesive component. The (meth) acrylic adhesive component or epoxy adhesive component is not particularly limited, and conventionally known (meth) acrylic adhesive components or epoxy adhesive components can be used.

The (meth) acrylic adhesive component may contain a monofunctional, bifunctional or trifunctional or higher (meth) acrylic monomer, or a (meth) acrylic oligomer in which a plurality of these (meth) acrylic monomers are bonded. preferable.
Examples of the monofunctional (meth) acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and diethylene glycol monoethyl ether. (Meta) acrylate, isobolonyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-acryloyloxyethyl-2-hydroxypropylphthalate, 2-methacloyloxyethyl-2-hydroxypropylphthalate, 2-hydroxyethyl acrylate , Glysidyl (meth) acrylate, urethane (meth) acrylate and the like.
Examples of the bifunctional (meth) acrylic monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tricyclodecanedimethanol diacrylate, and 1,6-hexane. Didioldimethacrylate, 1,9-nonanediol diacrylate, polytetramethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 2,2-bis [ Examples thereof include 4- (methacryloxyethoxy) phenyl] propandi (meth) acrylate.
Examples of the trifunctional or higher functional (meth) acrylic monomer include trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and tri (). Examples thereof include 2-acryloyloxyethyl) phosphate, tetramethylolmethanetri (meth) acrylate, tetramethylolpropanetetra (meth) acrylate, triallylisocianurate and derivatives thereof.
These (meth) acrylic monomers may be used alone or in combination of two or more. Among them, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and dihydroxyethyl acrylate are particularly excellent in compatibility with the modified polyvinyl acetal having the above-mentioned imine structure. , Glysidyl (meth) acrylate, urethane (meth) acrylate and the like are suitable.

The (meth) acrylic adhesive component preferably contains a polymerization initiator for reacting the (meth) acrylic monomer and the (meth) acrylic oligomer.
Examples of the polymerization initiator include 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, and 2,6-dimethoxy. Monoacylphosphine oxide compounds such as benzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,6-dimethylbenzoyl) -2, 4,4-trimethylpentylphosphine oxide, bis (2,6-dimethylbenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4,4- Trimethylpentylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2, Bisacylphosphine oxide compounds such as 4,6-trimethoxybenzoyl) -phenylphosphine oxide, benzophenol, acetophenone, 4,4'-dichlorobenzophenone, methylphenylglycolate, thioxanthone, 2,4-dimethyl Thioxanthone, 2-methylthioxanthone, 2-chlorthioxanthone, diisopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 2-isopropylthioxanthone, bis (η5-2,4-cyclopentadiene-1-yl)- Bis (2,6-difluoro-3- (1H-pyrrole-1-yl) -phenyl) titanium, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzoyl, camphorquinone, dibezosberone, 2-Ethylanthraquinone, 4', 4''-diethylisophthalofenone, 9,10-phenanthrenquinone, 1-phenyl-1,2-propandion-2-ethoxycarbonyloxym, benzophenone, methyl orthobenzoyl benzoate, ortho Benzoyl benzoic acid, 4-benzoyl-4'-methyldiphenyl sulfide, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)- Butanone-1,2-methyl-1- [4- (methylthio) pheni Le] -2-morpholinopropane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1 -On, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 4-phenylbenzophenone, hydroxybenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, benzoin, benzoin ethyl ether, benzoin isopropyl ether, Benzoin isobutyl ether, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 4-t-butyl-trichloroacetophenone, diethoxyacetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane- 1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, bis (4) -N-decanylphenyl) iodonium hexafluorophosphate, bis (an-dodecanylphenyl) iodonium hexafluoroantimonate, bis (4-tert-butylphenyl) iodonium bis (perfluorobutanesulfonyl) imide, bis ( 4-t-butylphenyl) iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, diphenyliodonium trifluoromethanesulfonate, 2- (3,4-dimethoxystyryl) -4,6-bis (trichloromethyl) -1 , 3,5-Triazine, 2- [2- (Fran-2-yl) Vinyl] -4,6-bis (trichloromethyl) -1,3,5-Triazine, 4-isopropyl-4'-methyldiphenyl Iodonium tetrakis (pentafluorophenyl) borate, 2- (4-methoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, triphenylsulfonium tetrafluoroborate, tri-p-tolyl Sulfonium HexafluoroPhosphate, Tri-p-Trillsulfonium Trifluoromethanesulfonate, Nifedipine, 2,5-Dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5- Di (t-butylperoxy) hexane-3-di-t-butyl peroxide, t-butylcumylpao Kiside, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, α, α'-bis (t-butylperoxyisopropyl) benzene, n-butyl-4,4 -Bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, t-butylperoxy-3,5,5-trimethylhexanoate, 1,1-bis (t-) Butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, benzoyl peroxide, t-butylperoxyacetate, methylethylketone peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, methylethylketone peroxide, 2,5- Dimethylhexyl-2,5-bisperoxybenzoate, t-butyl hydroperoxide, p-menthan hydroperoxide, p-chlorobenzoyl peroxide, t-hexyl peroxypivalate, hydroxyheptyl peroxide, chlorohexanone peroxide , Octanoyl peroxide, Decanoyl peroxide, Lauroyl peroxide, Cumylperoxyoctate, Succinic acid peroxide, Acetyl peroxide, t-Butylperoxy (2-ethylhexanoate), m-tol oil peroxide , T-Butylperoxyisobutyrate and 2,4-dichlorobenzoyl peroxide and other thermal polymerization initiators, or photopolymerization initiators such as persulfate, organic peroxide and azo compound. These polymerization initiators may be used alone or in combination of two or more.

The amount of the polymerization initiator blended in the (meth) acrylic adhesive component is not particularly limited, but the preferable lower limit with respect to 100 parts by weight of the (meth) acrylic monomer and (meth) acrylic oligomer is 0.01 parts by weight, which is a preferable upper limit. Is 10 parts by weight, the more preferable lower limit is 0.1 parts by weight, and the more preferable upper limit is 5 parts by weight.

The epoxy adhesive component preferably contains an epoxy monomer or an epoxy oligomer to which a plurality of these epoxy monomers are bonded.
Examples of the epoxy monomer include bisphenol A-based, bisphenol F-based, bisphenol AD-based, brom-containing bisphenol A-based, phenol novolac-based, cresol novolac-based, polyphenol-based, linear aliphatic-based, butadiene-based, urethane and other glycidyl. Ester-type epoxy monomers, hexahydrophthalic acid glycidyl esters, dimer-type glycidyl esters, aliphatic glycidyl ester-type epoxy monomers such as aromatics and cyclic aliphatics, bisphenol-based, ester-based, high-molecular-weight ether ester-based, Methyl-substituted epoxy monomers such as ether ester-based and brom-based novolac, heterocyclic epoxy monomers, glycidylamine-type epoxy monomers such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane, epoxidized polybutadiene, and large epoxys. Examples thereof include linear aliphatic type epoxy monomers such as soybean oil, cyclic aliphatic type epoxy monomers, naphthalene-based novolac type epoxy monomers, and diglycidyloxynaphthalene type epoxy monomers. These epoxy monomers may be used alone or in combination of two or more.

The epoxy adhesive component preferably contains a polymerization initiator for reacting the epoxy monomer and the epoxy oligomer.
Examples of the polymerization initiator include imidazoles, quaternary ammonium salts, phosphorus compounds, amines, phosphines, phosphonium salts, bicyclic amidins and their salts, acid anhydrides, phenols, cresols, xylenol, and the like. Novolak type phenol resin obtained by condensation reaction of resorcin and the like with formaldehyde, polymercapto resin such as liquid polymercaptan and polysulfide, thermal polymerization initiator such as amide, diphenyliodonium, 4-methoxydiphenyliodonium, bis (4) -Methylphenyl) iodonium, bis (4-tert-butylphenyl) iodonium, bis (dodecylphenyl) iodonium, diphenyl-4-thiophenoxyphenylsulfonium, bis [4- (diphenylsulfonio) -phenyl] sulfide, bis [ 4- (Di (4- (2-hydroxyethyl) phenyl) Sulfonio) -Phenyl] Sulfide, η5-2,4- (Cyclopentagenyl) [1,2,3,4,5,6-η-( Methylethyl) benzene] -A photopolymerization initiator composed of a compound consisting of a combination of a cation such as iron (1+) and an anion such as tetrafluoroborate, hexafluorophosphate, triphenylhexafluorophosphate and hexafluoroarsenate. Be done. These polymerization initiators may be used alone or in combination of two or more.

The amount of the polymerization initiator blended in the epoxy adhesive component is not particularly limited, but the preferable lower limit is 1 part by weight, the preferable upper limit is 300 parts by weight, and the more preferable lower limit is 300 parts by weight with respect to 100 parts by weight of the epoxy monomer and the epoxy oligomer. 10 parts by weight, more preferably the upper limit is 150 parts by weight.

The adhesive of the present invention contains a modified polyvinyl acetal having an imine structure (hereinafter, also simply referred to as "modified polyvinyl acetal"). As a result, the adhesive of the present invention can exhibit high impact resistance even in a harsh environment without impairing the adhesiveness.
The modified polyvinyl acetal contains a structural unit having an imine structure.
In the present specification, the imine structure means a structure having a C = N bond.
Examples of the structural unit having the imine structure include the structural unit represented by the following formula (1).

In formula (1), R ¹ represents a single bond or an alkylene group, and R ² represents a group having an imine structure.

In the above formula (1), when R ¹ is an alkylene group, the preferable lower limit of the number of carbon atoms of the alkylene group is 1, and the preferable upper limit is 12. If the number of carbon atoms of the alkylene group exceeds 12, the optimum strength may not be obtained. When the R ¹ is an alkylene group, the more preferable upper limit of the carbon number of the alkylene group is 5.

In the above formula (1), when R ¹ is an alkylene group, the alkylene group includes, for example, a methylene group, a dimethylene group (ethylene group), a trimethylene group (n-propylene group), and a tetramethylene group (n-butylene). Group), linear alkylene group such as pentamethylene group, hexamethylene group, octamethylene group, decamethylene group, methylmethylene group, methylethylene group, 1-methylpentylene group, 1,4-dimethylbutylene group and the like. Examples thereof include cyclic alkylene groups such as a alkylene group, a cyclopropylene group, a cyclobutylene group and a cyclohexylene group. Of these, linear alkylene groups such as methylene group, dimethylene group (ethylene group), trimethylene group (n-propylene group) and tetramethylene group (n-butylene group) are preferable, and methylene group and dimethylene group (ethylene group) are preferable. Is more preferable.

Examples of the R ² include functional groups represented by the following formula (2).

In the formula (2), R ³ represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and R ⁴ represents a hydrocarbon group having 1 to 18 carbon atoms.

Examples of the hydrocarbon group include saturated hydrocarbon groups, unsaturated hydrocarbon groups, aromatic hydrocarbon groups and the like. The hydrocarbon group may consist of only a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aromatic hydrocarbon group, or two or more of these may be used.

Examples of the saturated hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group and a hexyl group. , Heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group and the like. Of these, a methyl group, an ethyl group and an n-propyl group are preferable.
Examples of the aromatic hydrocarbon group include a phenyl group, a toluyl group, a xsilyl group, a t-butylphenyl group, a benzyl group and the like.

In the modified polyvinyl acetal, among the structural units having the imine structure, it is preferable that R ¹ is a single bond, R ³ is a hydrogen atom, and R ⁴ is a methyl group or an ethyl group.

In the modified polyvinyl acetal, the preferable lower limit of the content of the structural unit having an imine structure is 0.1 mol%, and the preferable upper limit is 20 mol%.
When the content of the structural unit having the imine structure is within this range, high impact resistance can be exhibited even in a harsh environment without impairing the adhesiveness, and the modified polyvinyl acetal is produced by acetalization, which will be described later. Is also easy. The more preferable lower limit of the content of the structural unit having an imine structure is 1.0 mol%, and the more preferable upper limit is 15 mol%.

The modified polyvinyl acetal may further contain a structural unit having an amino group or an amide structure. By having the amino group or the amide structure, a crosslinked structure can be formed with the (meth) acrylic adhesive component or the epoxy adhesive component. Among them, it is preferable to have the above amino group or amide structure in the side chain. Further, the amino group or amide structure may be directly bonded to the carbon constituting the main chain of the modified polyvinyl acetal, or may be bonded via a linking group such as an alkylene group. Further, the amino group may be a primary amine or a secondary amine.
In particular, the amino group is preferably −NH ₂ .
In the present invention, the amide structure means a structure having -C (= O) -NH-.
Among them, the structural unit having an amino group preferably has a structure represented by the following formula (3). The structural unit having the amide structure is preferably the structure represented by the following formula (4).

In formula (4), R ⁵ represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.
Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and a cycloalkenyl group.

When the modified polyvinyl acetal contains a structural unit having an amino group or an amide structure, the preferable lower limit of the content of the structural unit having an amino group or an amide structure is 0.1 mol%, and the preferable upper limit is 20 mol%. When the content of the structural unit having an amino group or an amide structure is within this range, the desired effect can be obtained. A more preferable lower limit of the content of the structural unit having an amino group or an amide structure is 0.5 mol%, and a more preferable upper limit is 10 mol%.

The degree of acetalization of the modified polyvinyl acetal is not particularly limited, but the preferable lower limit is 60 mol% and the preferable upper limit is 90 mol%. When the degree of acetalization is within this range, it is possible to obtain a two-component mixed adhesive having excellent compatibility with the (meth) acrylic adhesive component or the epoxy adhesive component and having excellent handleability. In addition, the modified polyvinyl acetal can be easily precipitated in the synthesis step by the precipitation method. The more preferable lower limit of the degree of acetalization is 65 mol%, and the more preferable upper limit is 85 mol%.
The degree of acetalization of the modified polyvinyl acetal is a value expressed as a percentage (mol%) of the molar fraction obtained by dividing the amount of ethylene groups to which the acetal groups are bonded by the total amount of ethylene groups in the main chain. is there. The degree of acetalization was determined by measuring the amount of acetyl groups and the amount of vinyl alcohol (content of hydroxyl groups) by a method based on JIS K6728 "Polyvinyl butyral test method", and calculating the molar fraction from the obtained measurement results. It can then be calculated by subtracting the amount of acetyl groups and the amount of vinyl alcohol from 100 mol%.

The amount of hydroxyl groups of the modified polyvinyl acetal is not particularly limited, but the preferable lower limit is 15 mol% and the preferable upper limit is 35 mol%. When the amount of the hydroxyl groups is within this range, higher adhesiveness can be exhibited. The more preferable lower limit of the amount of hydroxyl groups is 17 mol%, and the more preferable upper limit is 25 mol%.
The amount of hydroxyl groups in the modified polyvinyl acetal is a value expressed as a percentage (mol%) of the molar fraction obtained by dividing the amount of ethylene groups to which the hydroxyl groups are bonded by the total amount of ethylene groups in the main chain. The amount of ethylene groups to which the hydroxyl groups are bonded can be determined, for example, by a method based on JIS K6728 "Polyvinyl butyral test method".

The amount of the acetyl group of the modified polyvinyl acetal is not particularly limited, but the preferable lower limit is 0.0001 mol% and the preferable upper limit is 15 mol%. The more preferable lower limit of the amount of acetyl groups is 0.01 mol%, the more preferable upper limit is 10 mol%, the further preferable lower limit is 0.1 mol%, and the further preferable upper limit is 5 mol%.
The amount of acetyl groups in the modified polyvinyl acetal is the value obtained by subtracting the amount of ethylene groups to which the acetal group is bonded and the amount of ethylene groups to which the hydroxyl group is bonded from the total amount of ethylene groups in the main chain. It is a value expressed as a percentage (mol%) of the molar fraction obtained by dividing by the total ethylene group amount of. The amount of ethylene group to which the acetal group is bonded can be measured according to, for example, JIS K6728 “Polyvinyl butyral test method”.

The degree of polymerization of the modified polyvinyl acetal is not particularly limited, but the preferred lower limit is 100 and the preferred upper limit is 4500. When the degree of polymerization of the modified polyvinyl acetal is within this range, an adhesive having high adhesiveness and excellent handleability at room temperature can be obtained. The more preferable lower limit of the degree of polymerization is 150, and the more preferable upper limit is 4000.

As a method for preparing the modified polyvinyl acetal, for example, polyvinyl alcohol obtained by saponifying polyvinyl acetate obtained by copolymerizing a monomer having an imine structure with vinyl acetate has been conventionally known. There is a method of acetalizing by the method of. Further, a method of introducing an imine structure by acetalizing polyvinyl alcohol having a structural unit having an amino group or an amide structure by a conventionally known method may be used. Further, a method of acetalizing a modified polyvinyl alcohol having an imine structure obtained by post-modifying a polyvinyl alcohol having a structural unit having an amino group or an amide structure by a conventionally known method may be used. Further, the imine structure may be introduced by post-denaturing the unmodified polyvinyl acetal.

Among them, a method of introducing an imine structure by acetalizing polyvinyl alcohol having a structural unit having an amino group or an amide structure by a conventionally known method is preferable. According to such a method, the imine structure can be easily introduced by adding an excessive amount of the aldehyde and the acid catalyst used for acetalization.
When such a method is used, as a method for confirming the structural unit having an amino group or an amide structure and the structural unit having an imine structure, for example, FT-IR is used to obtain a spectrum of the amino group ( Examples include a method of confirming (around 1600 cm ^-1 ) and a method of confirming the spectrum (160 to 170 ppm) of the imine structure using ¹³ C-NMR.

The acetalization can be carried out by a known method, and is preferably carried out in an aqueous solvent, in a mixed solvent of water and an organic solvent compatible with water, or in an organic solvent.
As the organic solvent compatible with water, for example, an alcohol-based organic solvent can be used.
Examples of the organic solvent include alcohol-based organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol, aromatic organic solvents such as xylene, toluene, ethylbenzene, and methyl benzoate, and aromatic organic solvents. Aliper ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, ethyl acetoacetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl Ketone solvents such as cyclohexanone, benzophenone and acetophenone, lower paraffin solvents such as hexane, pentane, octane, cyclohexane and decane, and ethers such as diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether and propylene glycol diethyl ether. System solvents, amide solvents such as N, N-dimethylformamide, N, N-dimethyltesetamide, N-methylpyrrolidone, acetoanilide, aqueous ammonia, trimethylamine, triethylamine, n-butylamine, din-butylamine, trin- Examples thereof include amine-based solvents such as butylamine, aniline, N-methylaniline, N, N-dimethylaniline, and pyridine. These can be used alone or in combination of two or more kinds of solvents. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferable from the viewpoint of solubility in the resin and simplicity during purification.

The acetalization is preferably carried out in the presence of an acid catalyst.
The above acid catalyst is not particularly limited, and hydrogen halide such as hydrochloric acid, mineral acids such as nitrate, sulfuric acid and phosphoric acid, carboxylic acids such as formic acid, acetic acid and propionic acid, methanesulfonic acid, ethanesulfonic acid and benzene are not particularly limited. Examples thereof include sulfonic acids such as sulfonic acids and paratoluene sulfonic acids. These acid catalysts may be used alone or in combination of two or more compounds. Of these, hydrochloric acid, nitric acid, and sulfuric acid are preferable, and hydrochloric acid is particularly preferable.
In the method for introducing an imine structure by acetalizing the polyvinyl alcohol having a structural unit having an amino group or an amide structure, for example, an acid catalyst is added in an amount of 1.0% by weight or more to obtain an imine structure. It can be easily introduced.

Examples of the aldehyde used for the acetalization include aldehydes having a chain aliphatic group having 1 to 10 carbon atoms, a cyclic aliphatic group or an aromatic group. Conventionally known aldehydes can be used as these aldehydes. The aldehyde used in the acetalization reaction is not particularly limited, and for example, formaldehyde, acetaldehyde, propionaldehyde, n-butyl aldehyde, isobutyl aldehyde, n-barrel aldehyde, n-hexyl aldehyde, and 2-ethyl butyl aldehyde. , 2-Ethylhexyl aldehyde, n-heptyl aldehyde, n-octel aldehyde, n-nonyl aldehyde, n-decyl aldehyde and other aliphatic aldehydes, benzaldehyde, cinnam aldehyde, 2-methyl benzaldehyde, 3-methyl benzaldehyde, 4- Examples thereof include aromatic aldehydes such as methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. These aldehydes may be used alone or in combination of two or more. Among the aldehydes, butyraldehyde, 2-ethylhexylaldehyde, and n-nonylaldehyde, which have excellent acetalization reactivity, can bring about a sufficient internal plasticizing effect on the produced resin, and as a result can impart good flexibility. Is preferable, butyraldehyde is more preferable.

The amount of the aldehyde added may be appropriately set according to the degree of acetalization of the target modified polyvinyl acetal. In particular, when it is 60 to 95 mol%, preferably 70 to 90 mol% with respect to 100 mol% of polyvinyl alcohol, the acetalization reaction is efficiently carried out and unreacted aldehydes can be easily removed, which is preferable.

In the adhesive of the present invention, the preferable lower limit of the content of the modified polyvinyl acetal with respect to 100 parts by weight of the (meth) acrylic adhesive component or the epoxy adhesive component is 1 part by weight, and the preferable upper limit is 100 parts by weight. When the content of the modified polyvinyl acetal is within this range, it is possible to exhibit high impact resistance in a harsh environment while maintaining high reactivity. The more preferable lower limit of the blending amount of the modified polyvinyl acetal is 20 parts by weight, and the more preferable upper limit is 50 parts by weight.

The adhesive of the present invention further comprises natural rubber, polystyrene-based, polyolefin-based, polydiene-based, polyvinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, fluorine-based, chlorinated polyethylene-based, polynorbornene-based, and polystyrene. Elastomers exhibiting rubber elasticity such as polyolefin copolymer system, (hydrogenated) polystyrene / butadiene copolymer system, polystyrene / vinyl polyisoprene copolymer system, chlorosulfonated polyethylene, ethylene acrylic rubber, ditryl rubber, chloroprene polymer, etc. It may contain a high molecular weight compound. By containing such a high molecular weight compound, the cohesive force of the adhesive is improved.

When the adhesive of the present invention contains the high molecular weight compound, the preferable upper limit of the content of the high molecular weight compound with respect to 100 parts by weight of the (meth) acrylic adhesive component or the epoxy adhesive component is 200 parts by weight. .. When the content of the high molecular weight compound is less than 200 parts by weight, the cohesive force of the adhesive can be improved while maintaining excellent reactivity. A more preferable upper limit of the blending amount of the high molecular weight compound is 35 parts by weight.

The adhesive of the present invention further comprises a tackifier resin, an adhesive strength modifier, an emulsifier, an antioxidant, a softener, fine particles, a filler, a pigment, a dye, a silane coupling agent, an antioxidant, a surfactant, and a wax. It may contain a known additive such as.

The adhesive of the present invention can be suitably used for adhering materials such as aircraft structural materials, which are required to have both high adhesiveness and high impact resistance in a harsh environment.
An aircraft adhesive comprising the impact resistant adhesive of the present invention is also one of the present inventions.

According to the present invention, it is possible to provide an impact-resistant adhesive having excellent adhesiveness and impact resistance, and an aircraft adhesive composed of the impact-resistant adhesive.

It is a schematic diagram explaining the test piece used for the tensile shear adhesive strength test method of the adhesive in an Example. It is a schematic diagram explaining the wedge-peeling test method in an Example.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Preparation of modified polyvinyl butyral>
240 g of polyvinyl alcohol containing a degree of polymerization of 600, a degree of saponification of 99 mol%, and 1.7 mol% of a structural unit having an amino group (-NH ₂ ) represented by the above formula (3) was added to 1800 g of pure water, and the temperature was 90 ° C. Was stirred for about 2 hours to dissolve. This solution was cooled to 40 ° C., 170 g of hydrochloric acid having a concentration of 35% by weight and 275 g of n-butyraldehyde were added thereto, and the liquid temperature was maintained at 40 ° C. to carry out an acetalization reaction to precipitate a reaction product. It was.
Then, the liquid temperature was kept at 40 ° C. for 3 hours to complete the reaction, and the powder was neutralized, washed with water and dried by a conventional method to obtain a modified polyvinyl butyral powder.

The obtained modified polyvinyl butyral was dissolved in DMSO-d ₆ (dimethyl sulfoxide) and analyzed using ¹³ C-NMR (nuclear magnetic resonance spectrum). As a result, the degree of butyralization was 77.5 mol% and the amount of hydroxyl groups. 20.0 mol%, the amount of acetyl group is 0.4 mol%, and the content of the structural unit having an imine structure (R ³ and R ⁴ are methyl groups) represented by the following formula (5) is 1.7. It was confirmed that it was mol%.

<Preparation of polyvinyl butyral>
250 g of polyvinyl alcohol having a degree of polymerization of 650 and a degree of saponification of 99 mol% was added to 1800 g of pure water, and the mixture was dissolved by stirring at a temperature of 90 ° C. for about 2 hours. This solution was cooled to 40 ° C., 170 g of hydrochloric acid having a concentration of 35% by weight and 275 g of n-butyraldehyde were added thereto, and the liquid temperature was maintained at 40 ° C. to carry out an acetalization reaction to precipitate a reaction product. It was.
Then, the liquid temperature was maintained at 40 ° C. for 3 hours to complete the reaction, and the powder was neutralized, washed with water and dried by a conventional method to obtain a polyvinyl butyral powder.

The obtained polyvinyl butyral was dissolved in DMSO-d ₆ (dimethyl sulfoxide) and analyzed using ¹³ C-NMR (nuclear magnetic resonance spectrum). As a result, the degree of acetalization was 65.0 mol% and the amount of hydroxyl groups was It was confirmed that 34.0 mol% and the amount of acetyl groups were 1.0 mol%.

(Example 1)
34 parts by weight of tricyclodecanedimethanol diacrylate (bifunctional acrylate monomer, "SR833S" manufactured by Sartmer), 33 parts by weight of ethyl acrylate (monofunctional acrylate monomer, manufactured by Nippon Catalyst), 2-hydroxyethyl acrylate (monofunctional acrylate) Add 33 parts by weight of monomer (manufactured by Wako Pure Chemical Industries, Ltd.) and 5 parts by weight of t-butylperoxy-3,5,5-trimethylhexanoate ("perbutyl355" manufactured by Nichiyu Co., Ltd.) as a photopolymerization initiator. Obtained an acrylic adhesive component.
To 100 parts by weight of the obtained acrylic adhesive component, 1 part by weight of modified polyvinyl butyral was added, and the mixture was sufficiently stirred and mixed to obtain an adhesive.

(Examples 2 to 3, Comparative Examples 1 to 5)
An adhesive similar to that of Example 1 was obtained except that 1 part by weight of the modified polyvinyl butyral was used as shown in Table 1.
As the elastomer, a styrene-butadiene-styrene copolymer (SBS, “Kraton D1116” manufactured by Kraton Polymer Japan, Inc.) was used.

(Evaluation)
The adhesives obtained in Examples and Comparative Examples were evaluated by the following methods.
The results are shown in Table 1.

(1) Evaluation of Adhesiveness A test piece was prepared as shown in FIG. 1 according to the tensile shear adhesive strength test method of the adhesive of JIS K 6850. An aluminum plate (“A1050” manufactured by Nippon Test Panel Co., Ltd.) was used as a substrate to be evaluated, and an adhesive was applied to the substrate for adhesion, and then the substrate was cured by heating at 130 ° C. for 30 minutes. Then, the tensile shear adhesive strength at 23 ° C. was measured using a Tensilon universal material tester (RTC-1350A, manufactured by A & D Co., Ltd.).

(2) Evaluation of Impact Resistance under Severe Environment The test as shown in FIG. 2 was carried out according to the measurement test (wedge-peeling test) of the adhesive bond strength under impact of ISO11343. First, an aluminum plate (“A1050” manufactured by Nippon Test Panel Co., Ltd.) was used as the substrate 52 to be evaluated, and after the adhesive 51 was applied to the substrate and adhered, the substrate was heated at 130 ° C. for 30 minutes to be cured and tested. I got 5 pieces. Then, in an environment of −20 ° C., an impact energy of 20 J was applied to the test piece 5 by dropping a weight 6 having a wedge 7 at the tip at a speed of 2 m / sec. The case where the test piece 5 was not peeled off due to the impact was evaluated as “◯”, and the case where the test piece 5 was peeled off was evaluated as “x”.

(Example 4)
2,4-Diamino-6- [2'-undecyl imidazolyl- (1') as an imidazole-based curing catalyst with respect to 80 parts by weight of bisphenol A type liquid epoxy resin ("jER828" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 190). )]-Epoxy-s-triazine (“C11Z-A” manufactured by Shikoku Kasei Co., Ltd.) by 20 parts by weight was added to obtain an epoxy adhesive component.
To 100 parts by weight of the obtained epoxy-based adhesive component, 10 parts by weight of modified polyvinyl butyral was added, and the mixture was sufficiently stirred and mixed to obtain an adhesive.

(Example 5, Comparative Examples 6 to 8)
An adhesive similar to that of Example 4 was obtained except that 10 parts by weight of the modified polyvinyl butyral was used as shown in Table 2.
As the elastomer, a styrene-butadiene-styrene copolymer (SBS, “Kraton D1116” manufactured by Kraton Polymer Japan, Inc.) was used.

(Evaluation)
The adhesives obtained in Examples and Comparative Examples were evaluated by the above method.
The results are shown in Table 2.

According to the present invention, it is possible to provide an impact-resistant adhesive having excellent adhesiveness and impact resistance, and an aircraft adhesive composed of the impact-resistant adhesive.

1 Substrate 2 Support (same thickness and quality as substrate material)
3 Adhesive part 4 Grasp part 5 Test piece 51 Adhesive 52 Substrate 6 Weight 7 Wedge

Claims (3)

It contains a (meth) acrylic adhesive component or an epoxy adhesive component and a modified polyvinyl acetal having an imine structure.
The modified polyvinyl acetal having the imine structure is contained in an amount of 1 to 100 parts by weight based on 100 parts by weight of the (meth) acrylic adhesive component or the epoxy adhesive component.
The modified polyvinyl acetal having an imine structure contains a structural unit represented by the following formula (1).
The (meth) acrylic-based adhesive component comprises a monofunctional and / or difunctional (meth) acrylic monomers, as well as a photopolymerization initiator,
The impact-resistant adhesive, wherein the epoxy-based adhesive component contains an epoxy monomer and an imidazole-based compound.

In the formula (1), R ¹ represents a single bond or an alkylene group, and R ² represents a group having an imine structure represented by the following formula (2). When R ¹ is an alkylene group, the alkylene group has 1 to 12 carbon atoms.

In the formula (2), R ³ represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and R ⁴ represents a hydrocarbon group having 1 to 18 carbon atoms. The impact-resistant adhesive according to claim 1, wherein the modified polyvinyl acetal having an imine structure has a content of a structural unit having an imine structure of 0.1 mol% or more and 20 mol% or less. An aircraft adhesive comprising the impact-resistant adhesive according to claim 1 or 2.

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