Primer composiiton and adhesion method

Abstract

A primer composition for a porous substrate, said primer composition: containing (A) a (meth)acrylic copolymer having an alkoxysilyl group, (B) an adhesion improver comprising a reaction mixture of (B1) and / or (B2), (B1) being a reaction mixture of a polyfunctional isocyanate compound and a mercapto alkylsilane compound and (B2) being a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound, and (C) an organic solvent; and exhibiting good adhesion properties even after a processing (application and curing) site has been immersed in water.

Description

Primer composition and adhesion method

[0001] The present invention relates to a primer composition for porous substrates, and in particular to a primer composition that bonds a silicone resin, such as a cured product (cured silicone rubber product) of a room-temperature condensation-curable silicone rubber composition or an addition-curable silicone rubber composition, to a porous substrate and that maintains good adhesion even after immersion in water, and a method for bonding a silicone resin to a porous substrate using the primer composition.

[0002] Cured products of silicone rubber compositions (silicone rubber cured products) selected from room-temperature condensation-curable silicone compositions and addition-curable silicone compositions are used in many fields (such as sealing materials for building materials and adhesives in the electrical and electronic fields) due to their excellent heat resistance, cold resistance, weather resistance, electrical insulation, safety, etc., and are often used as parts combined with various substrates. Generally, in order to adhere cured products of these silicone rubber compositions to various substrates, a method is adopted in which a primer composition is applied to the substrate (adherend) in advance.

[0003] Known primers include carbon functional silanes, such as aminoalkylsilanes, which have functional groups that can react with one component of a silicone rubber composition. However, these primers have the disadvantage that the presence of moisture at the application site reduces adhesive strength and, in some cases, can cause peeling. In particular, when the adherend is a porous material, the presence of many voids can lead to moisture in the material. This means that the primer layer (coated surface) is susceptible to moisture not only from the outer surface but also from the material itself, causing a decrease in adhesion and making the primer more susceptible to peeling. Furthermore, when outdoor use is anticipated, even if the material is sufficiently dry at the time of application, it may still be affected by rainwater, so high water resistance is required.

[0004] Among porous materials, wood in particular is seeing increased use in recent years due to the promotion of carbon neutrality. However, there are few examples of the use of room-temperature condensation-curing silicone compositions and addition-curing silicone compositions on wood as an adherend. In addition, because wood itself contains moisture and resin, it is difficult to achieve adhesive properties from these compositions. Furthermore, it is extremely difficult to maintain sufficient adhesive properties even after the applied (applied and cured) area has been immersed in water (submerged).

[0005] In this regard, Japanese Patent Laid-Open Publication No. 11-209682 (Patent Document 1) describes a composition made of an acrylic copolymer that exhibits high adhesive strength even when immersed in an alkaline aqueous solution.

[0006] Furthermore, Japanese Patent Laid-Open Publication No. 48-75633 (Patent Document 2) describes that by reacting an aminoalkylalkoxysilane with an epoxyalkylalkoxysilane under specified conditions to form an adhesion promoter, the applied (applied and cured) area maintains its adhesive strength even after immersion in water.

[0007] However, Patent Document 1 is based on the premise that concrete, which may be affected by alkalinity, is used as the substrate, and Patent Document 2 evaluates glass or aluminum as the substrate, and neither evaluates the adhesiveness, particularly the water-resistant adhesiveness, of porous materials as the substrate.

[0008] JP-A-11-209682 JP-A-48-75633

[0009] The present invention has been made in view of the above circumstances, and aims to provide a primer composition for porous substrates, particularly wood, which exhibits good adhesion even after the application (applied and cured) area is immersed in water, and a method for bonding a silicone resin to a porous substrate.

[0010] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they discovered that adding a reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane and / or a reaction mixture of a polyfunctional epoxy monomer and an aminoalkylsilane is effective in improving the adhesion, particularly water-resistant adhesion, of a primer composition for porous substrates at the application (coating and curing) point. They also discovered that combining a hydrolyzable organosilane compound with an acrylic copolymer containing an alkoxysilyl group is extremely effective, leading to the completion of the present invention.

[0011] That is, the present invention provides the following primer composition and adhesion method. [1] A primer composition for a porous substrate, comprising: (A) a (meth)acrylic copolymer having an alkoxysilyl group; (B) an adhesion improver comprising a reaction mixture of the following components (B1) and / or (B2); (B1) a reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound; (B2) a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound; and (C) an organic solvent. [2] The primer composition according to [1], wherein the component (B1) is further a reaction mixture of a hydrolyzable organosilane compound having no amino groups or mercapto groups and / or a partial hydrolyzed condensate thereof. [3] The primer composition according to [1] or [2], wherein the component (B2) is further a reaction mixture of a hydrolyzable organosilane compound having no amino groups or mercapto groups and / or a partial hydrolyzed condensate thereof. [4] The primer composition according to any one of [1] to [3], wherein the component (B2) contains an epoxy prepolymer represented by the following average composition formula (1): (In formula (1), X is independently a divalent hydrocarbon group having 1 to 31 carbon atoms which may contain an oxygen atom, a nitrogen atom, or a sulfur atom; R １ are independently an alkylene group having 3 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and R ２ and R ３are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, l is independently 1 or 2, m is independently a number from 0 to 3, and n is a number from 0 to 50.) [5] The primer composition according to any one of [1] to [4], wherein the component (B2) comprises a reaction product of a polyfunctional epoxy compound represented by the following general formula (2), an aminoalkylsilane compound represented by the general formula (3), and a hydrolyzable organosilane compound having no amino group or mercapto group represented by the general formula (4): (In formula (2), X represents a divalent hydrocarbon group having 1 to 31 carbon atoms and optionally containing an oxygen atom, a nitrogen atom, or a sulfur atom, and having at least one of an alkylene group which may have a branched structure, a monocyclic structure, and a polycyclic structure.) (In formula (3), R １ is an alkylene group having 3 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and R ２ and R ３ are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, and m is a number from 0 to 3. (In formula (4), R ２ and R ３are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, and l' is 2 or 3.) [6] The primer composition according to [5], wherein the aminoalkylsilane compound is γ-aminopropyltrimethoxysilane or γ-aminopropyltriethoxysilane. [7] The primer composition according to any one of [1] to [6], further comprising (D) a hydrolyzable organosilane compound and / or a partial hydrolyzed condensate thereof. [8] The primer composition according to any one of [1] to [7], wherein the (meth)acrylic copolymer of component (A) is a copolymer of a (meth)acrylic acid ester monomer having an alkoxysilyl group and a (meth)acrylic acid ester monomer not having an alkoxysilyl group. [9] The primer composition according to [8], wherein the content of the (meth)acrylic acid ester monomer having an alkoxysilyl group in the total monomer components of component (A) is 1 to 30 mass%.

[10] The primer composition according to any one of [1] to [9], wherein the component (C) is any one or a mixture of two or more selected from aromatic hydrocarbon solvents, alcohol solvents, ketone solvents, ether solvents, ester solvents, and paraffin solvents.

[11] The primer composition according to any one of [1] to

[10] , wherein the component (C) has a flash point of -40°C or higher, a boiling point of 41°C or higher, and an auto-ignition point of 101°C or higher.

[12] The primer composition according to any one of [1] to

[11] , wherein the primer composition is used to bond a cured product of a room-temperature condensation-curable silicone rubber composition or an addition-curable silicone rubber composition to a porous substrate.

[13] The primer composition according to any one of [1] to

[12] , wherein the primer composition is used to improve water-resistant adhesion.

[14] The primer composition according to any one of [1] to

[13] , wherein the porous substrate is made of wood.

[15] A method for adhering a silicone resin to a porous substrate, comprising the steps of: applying the primer composition according to any one of [1] to

[14] to the surface of a porous substrate to form a primer layer; and then applying and curing a room-temperature condensation-curable silicone rubber composition or an addition-curable silicone rubber composition to the surface of the primer layer to form a silicone resin layer made of a cured silicone rubber.

[16] The bonding method according to

[15] , which improves the water-resistant adhesion between the silicone resin and the porous substrate.

[0012] The primer composition of the present invention is applied to the surface of a porous substrate to form a primer layer, and thereby the resulting silicone resin layer, such as a cured product (cured silicone rubber product) of a silicone rubber composition selected from a room-temperature condensation-curable silicone composition and an addition-curable silicone composition, formed thereon, can be well adhered to the porous substrate, and good adhesion can be maintained even after immersion in water.

[0013] The present invention will be described in detail below, but is not limited thereto. In the present invention, "(meth)acrylic copolymer" refers to either or both of an acrylic copolymer and a methacrylic copolymer, "acrylic copolymer" refers to a copolymer having an acrylic (also called acryloyl) group, and "methacrylic copolymer" refers to a copolymer having a methacrylic (also called methacryloyl) group. "(Meth)acrylic acid ester" refers to either or both of an acrylic acid ester and a methacrylic acid ester.

[0014] [Primer composition] The primer composition of the present invention is for use on porous substrates and contains: (A) a (meth)acrylic copolymer having an alkoxysilyl group; (B) an adhesion improver consisting of a reaction mixture of the following components (B1) and / or (B2); (B1) a reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound; (B2) a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound; and (C) an organic solvent.

[0015] - Component (A) - The component (A) is a (meth)acrylic copolymer having an alkoxysilyl group, and in particular, an acrylic copolymer obtained by copolymerizing a monomer component containing a (meth)acrylic acid ester having an alkoxysilyl group and a (meth)acrylic acid ester not having an alkoxysilyl group, and has the function of forming a film on an adherend.

[0016] The acrylic copolymer constituting component (A) is obtained by copolymerizing monomer components including at least one type of (meth)acrylic acid ester having an alkoxysilyl group in the molecule (hereinafter referred to as alkoxysilyl group-containing component (A1)) and at least one type of (meth)acrylic acid ester not having an alkoxysilyl group in the molecule (hereinafter referred to as alkoxysilyl group-free component (A2)).

[0017] The polymerization method for copolymerizing the above-mentioned monomer components is not particularly limited, and examples thereof include radical polymerization, cationic polymerization, anionic polymerization, etc. Among these, random radical polymerization using an organic peroxide or an organic azo compound as an initiator is effective as a simple method.

[0018] The alkoxysilyl group-containing component (A1) is a monomer component containing at least one (meth)acrylic acid ester having an alkoxysilyl group in the molecule. In this monomer, the (meth)acrylic acid ester having an alkoxysilyl group can be used alone or in combination of two or more. Furthermore, the (meth)acrylic acid ester having an alkoxysilyl group has at least one, preferably two or three, alkoxysilyl groups in one molecule.

[0019] Examples of the (meth)acrylic acid ester having an alkoxysilyl group in the molecule include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane. Of these, 3-(meth)acryloxypropyltrimethoxysilane is particularly preferred.

[0020] The content of this alkoxysilyl group-containing component (A1) is 1 to 30% by mass, and preferably 1 to 20% by mass, when the mass of all the monomer components used to obtain component (A) (the sum of components (A1) and (A2)) is taken as 100% by mass. If the content of component (A1) is less than 1% by mass or more than 30% by mass of the total monomers used to obtain component (A), adhesion to the adherend may be impaired.

[0021] The alkoxysilyl group-free component (A2) is a monomer component containing at least one (meth)acrylic acid ester that does not have an alkoxysilyl group in the molecule, and the alkoxysilyl group-free (meth)acrylic acid ester in this monomer can be used alone or in combination of two or more.

[0022] Furthermore, examples of (meth)acrylic acid esters not having an alkoxysilyl group include acrylic acid esters and methacrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate, isopentyl acrylate, n-hexyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and isobornyl acrylate; and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, and isobornyl methacrylate. The (meth)acrylic acid ester not containing an alkoxysilyl group is preferably an aliphatic hydrocarbon ester of (meth)acrylic acid, more preferably an alkyl (meth)acrylic acid ester having an alkyl group with a carbon number of 1 to 20, and even more preferably an alkyl (meth)acrylic acid ester having an alkyl group with a carbon number of 1 to 10. Of these, particularly preferred are methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and tert-butyl (meth)acrylate.

[0023] The content of this alkoxysilyl group-free component (A2) is 70 to 99% by mass, and preferably 80 to 99% by mass, when the mass of all the monomer components used to obtain component (A) (the sum of components (A1) and (A2)) is taken as 100% by mass. If the content of component (A2) is less than 70% by mass or more than 99% by mass of all the monomers used to obtain component (A), adhesion to the adherend may be impaired.

[0024] The blending amount of component (A) is 2 to 100 parts by mass, and preferably 5 to 50 parts by mass, per 10 parts by mass of component (B) described below. If the blending amount of component (A) is too small, adhesiveness may be impaired, whereas if it is too large, uneven coating may occur when applied to an adherend.

[0025] - Component (B) - The component (B) is an adhesion improver comprising a reaction mixture of the following components (B1) and / or (B2): (B1) a reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound, and (B2) a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound.

[0026] (Component (B1)) The reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound of component (B1) is an adduct of a polyfunctional isocyanate compound (a monomer and / or a polymer thereof having two or more isocyanate groups in the molecule) and a mercaptoalkylsilane compound (a hydrolyzable mercaptoalkylsilane and / or a hydrolyzed condensation polymer thereof) (i.e., an addition reaction product in which a mercapto group in a mercaptoalkylsilane compound is added to an isocyanate group in a polyfunctional isocyanate compound), and functions as a film-forming component and an adhesive component.

[0027] Examples of polyfunctional isocyanate compounds include aliphatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, naphthalene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate methyl ester; isocyanurate silanes such as tris(trimethoxysilyl)isocyanurate; and polymers or partial hydrolysates of isocyanate group-containing silane compounds such as isocyanate group-containing mercaptosilane, γ-isocyanate propyl trimethoxysilane, γ-isocyanate propyl triethoxysilane, γ-isocyanate propyl methyl diethoxysilane, and γ-isocyanate propyl methyl dimethoxysilane. These may be used alone or in combination of two or more.

[0028] Examples of mercaptoalkylsilane compounds include hydrolyzable organosilane compounds (silane coupling agents) that have a mercapto group and two or three hydrolyzable groups, such as alkoxy groups, bonded to silicon atoms in the molecule, such as mercapto group-containing silanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-mercaptopropylmethyldiethoxysilane, and / or hydrolyzed condensation polymers thereof. Excellent film-forming ability is particularly observed when the molecule has three or more hydrolyzable groups, and trialkoxymercaptoalkylsilanes such as γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane are preferred. These silane coupling agents may be used alone or in combination of two or more.

[0029] In the addition reaction of the polyfunctional isocyanate compound and the mercaptoalkylsilane compound, the amount of the mercaptoalkylsilane compound is preferably 0.01 to 100 moles, more preferably 0.1 to 10 moles, of mercapto groups per mole of the isocyanate group of the polyfunctional isocyanate compound.

[0030] The method for synthesizing the reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound is not particularly limited, but for example, when the mercaptoalkylsilane compound is hydrolyzable, the polyfunctional isocyanate compound and the mercaptoalkylsilane compound may be mixed for 30 minutes to 12 hours at room temperature (23±15° C.) in a moisture-protected state. At this time, an organic solvent such as toluene or ethyl acetate, which will be the component (C) described below, may be used, and a reaction catalyst (catalytic amount) such as tin 2-ethylhexanoate may be added.

[0031] Examples of the reaction catalyst include non-metallic organic catalysts and metallic catalysts.

[0032] Known non-metallic organic catalysts can be used, and examples thereof include, but are not limited to, phosphazene-containing compounds such as N,N,N',N',N'',N''-hexamethyl-N'''-(trimethylsilylmethyl)-phosphorimidic triamide; amine compounds or salts thereof such as n-octylamine, hexylamine, dodecylamine phosphate, and tetramethylguanidine; quaternary ammonium salts such as benzyltriethylammonium acetate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; tetramethylguanidylpropyltrimethoxysilane, tetramethylguanidylpropylmethyldimethoxysilane, and tetramethylguanidylpropyltris(trimethylsiloxy)silane. The non-metallic organic catalysts may be used alone or in combination of two or more.

[0033] Known metal catalysts can be used, including, for example, organotin compounds such as tin 2-ethylhexanoate (tin octoate), dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctoate, dioctyltin dineodecanoate, and di-n-butyl-dimethoxytin; titanate esters or titanium chelate compounds such as tetraisopropoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexoxy)titanium, dipropoxybis(acetylacetonato)titanium, and titanium isopropoxyoctylene glycol; zinc naphthenate, zinc stearate, and zinc-2-ethyloctanoate. Examples of metal catalysts include, but are not limited to, aluminum alcoholate compounds such as aluminum ctoate, iron 2-ethylhexoate, cobalt 2-ethylhexoate, manganese 2-ethylhexoate, cobalt naphthenate, aluminum isopropylate, and aluminum secondary butylate; aluminum chelate compounds such as aluminum alkyl acetate diisopropylate and aluminum bisethylacetoacetate monoacetylacetonate; and organic bismuth compounds such as bismuth(III) neodecanoate, bismuth(III) 2-ethylhexanoate, bismuth(III) citrate, and bismuth octoate. Furthermore, the metal catalysts may be used alone or in combination of two or more.

[0034] The amount of the reaction catalyst added is preferably 0.001 to 10% by mass, and more preferably 0.01 to 1% by mass, of the total amount of component (B1) (excluding any organic solvent added during the synthesis). Within this range, the reaction of component (B1) can be promoted without affecting adhesion.

[0035] (Component (B2)) The reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound of component (B2) is an adduct of a polyfunctional epoxy compound (a monomer and / or a polymer thereof having two or more epoxy groups in the molecule) and an aminoalkylsilane compound (a hydrolyzable aminoalkylsilane and / or a hydrolyzed condensation polymer thereof) (i.e., an addition reaction product in which an amino group in the aminoalkylsilane compound has undergone an addition reaction with (a part of) an epoxy group in the polyfunctional epoxy compound), and functions as a film-forming component and an adhesive component.

[0036] The polyfunctional epoxy compound is a polyfunctional monomer having two or more epoxy groups in the molecule and containing no reactive functional groups other than the epoxy group, and is preferably one containing two glycidyl ether groups and / or alicyclic epoxy groups, and more preferably an aliphatic epoxy compound containing two glycidyl ether groups.

[0037] Examples of polyfunctional epoxy compounds include 1,2-cyclohexanedicarboxylate diglycidyl, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and bisphenol AF diglycidyl ether. Other examples include polymers or partial hydrolysates of epoxy group-containing silane compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxysilane, and 3-glycidoxypropyldiethoxysilane. From the viewpoints of cost and solubility in solvents, bisphenol A diglycidyl ether is preferred. These compounds may be used alone or in combination of two or more.

[0038] Examples of aminoalkylsilane compounds include hydrolyzable organosilane compounds (silane coupling agents) having an alkyl group substituted with a primary amino group and / or a secondary amino group in the molecule and two or three hydrolyzable groups such as alkoxy groups bonded to silicon atoms in the molecule, such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, 3-2-(aminoethylamino)propyltrimethoxysilane, and 3-2-(aminoethylamino)propyltriethoxysilane, and / or hydrolyzed condensation polymers thereof (organosiloxane oligomers having an alkyl group substituted with a primary amino group and / or a secondary amino group in the molecule and residual hydrolyzable groups such as alkoxy groups). In particular, compounds having a primary amino group and a methoxy group exhibit excellent film-forming ability and adhesive properties, and γ-aminopropyltrimethoxysilane, 3-2-(aminoethylamino)propyltrimethoxysilane, etc. are preferred. These compounds may be used alone or in combination of two or more.

[0039] For the addition reaction of a polyfunctional epoxy compound and an aminoalkylsilane compound, the amount of the aminoalkylsilane compound is preferably 0.01 to 100 moles, more preferably 0.1 to 10 moles, of amino groups per mole of epoxy groups of the polyfunctional epoxy compound.

[0040] The method for synthesizing the reaction mixture of the polyfunctional epoxy compound and the aminoalkylsilane compound is not particularly limited. For example, when the aminoalkylsilane compound is hydrolyzable, the polyfunctional epoxy compound and the aminoalkylsilane compound may be mixed for 4 to 12 hours at a temperature of 40 to 90°C in a moisture-blocked state.

[0041] As component (B), either one of the reaction mixtures of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound (component (B1)) and a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound (component (B2)) may be used alone or in combination of two or more. When components (B1) and (B2) are used in combination, the mass ratio of components (B1) to (B2) is preferably 100:1 to 1:100, and more preferably 50:1 to 1:50.

[0042] As component (B), the reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound (B1) may be a reaction mixture with a hydrolyzable organosilane compound having no amino group or mercapto group and / or a partial hydrolyzed condensate thereof, and the reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound (B2) may be a reaction mixture with a hydrolyzable organosilane compound having no amino group or mercapto group and / or a partial hydrolyzed condensate thereof.

[0043] Examples of hydrolyzable organosilane compounds that do not have an amino group or a mercapto group include ketoxime group-containing silanes such as methyltris(methylethylketoxime)silane, vinyltris(methylethylketoxime)silane, phenyltris(methylethylketoxime)silane, and methyltris(dimethylketoxime)silane; alkoxysilanes such as methyltrimethoxysilane, octyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, and 2-ethylhexyl α-(dimethoxymethylsilyl)propionate; isopropenoxy group-containing silanes such as methyltriisopropenoxysilane, ethyltriisopropenoxysilane, vinyltriisopropenoxysilane, and phenyltriisopropenoxysilane; acetoxysilanes such as methyltriacetoxysilane, ethyltriacetoxysilane, and vinyltriacetoxysilane; and partial hydrolysis condensates of these silanes. These may be used alone or in combination of two or more.

[0044] When added, the content of the hydrolyzable organosilane compound and / or its partial hydrolysis condensate in component (B) that does not have an amino group or a mercapto group is preferably 1 to 50 mass %, and more preferably 5 to 40 mass %, of component (B1) or (B2). By keeping it within this range, the storage stability of the composition can be improved.

[0045] The epoxy prepolymer contained in the component (B2), which is a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound, further contains a hydrolyzable organosilane compound not having an amino group and / or a partial hydrolyzed condensate thereof, is further described below. In the present invention, the component (B2), which is a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound, further contains a hydrolyzable organosilane compound not having an amino group and / or a partial hydrolyzed condensate thereof, contains the epoxy prepolymer described below as a main component. Here, "containing the epoxy prepolymer as a main component" means that the reaction mixture contains the epoxy prepolymer in an amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

[0046] [Epoxy Prepolymer] The epoxy prepolymer contained in the reaction mixture of component (B2), which is a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound, further contains a hydrolyzable organosilane compound having no amino group and / or a partial hydrolyzed condensate thereof, is represented by the following average composition formula (1): (In formula (1), X is independently a divalent hydrocarbon group having 1 to 31 carbon atoms which may contain an oxygen atom, a nitrogen atom, or a sulfur atom; R １ are independently an alkylene group having 3 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and R ２ and R ３ are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, l is independently 1 or 2, m is independently a number from 0 to 3, and n is a number from 0 to 50.

[0047] In formula (1), X is independently a divalent hydrocarbon group having 1 to 31 carbon atoms which may contain an oxygen atom, a nitrogen atom, or a sulfur atom. Examples of the divalent hydrocarbon group include a linear or branched alkylene group having 1 to 20 carbon atoms, and a cyclic divalent hydrocarbon group having 3 to 31 carbon atoms (a monocyclic divalent hydrocarbon group or a polycyclic divalent hydrocarbon group). X may contain one or more of these groups and may contain an oxygen atom, a nitrogen atom, or a sulfur atom.

[0048] The number of carbon atoms in X is 1 to 31, preferably 1 to 20. Examples of linear alkylene groups include methylene, ethylene, n-propylene (trimethylene), n-butylene (tetramethylene), and n-hexylene (hexamethylene). Examples of branched alkylene groups include isobutylene, sec-butylene, isopentylene, isohexylene, isooctylene, and 2-ethylhexylene. Examples of monocyclic divalent hydrocarbon groups include 1,2- and 1,3-cyclopentylene and 1,4-cyclohexylene. Examples of polycyclic divalent hydrocarbon groups include 1,3-, 1,4-, and 1,5-naphthylene and anthrylene. Examples of structures containing oxygen, nitrogen, or sulfur atoms include carbonyl groups, ether bonds, and amino groups. X preferably contains an arylene group, more preferably a phenylene group. X is particularly preferably a divalent hydrocarbon group having 1 to 20 carbon atoms, which may contain an oxygen atom and / or a sulfur atom, and which has an oxygen atom at each of its two ends, and which forms an ether bond (C-O-C bond) between each of the adjacent carbon atoms to which X is bonded.

[0049] Specific examples of X include those represented by the following formulas (5a) to (5g). The dashed lines in the formulas indicate bonds. In particular, the following formula (5d) is preferred from the standpoints of cost and solubility in a solvent during primer preparation.

[0050]

[0051] R １are independently an alkylene group having 3 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and examples thereof include alkylene groups such as an n-propylene (trimethylene) group, an isopropylene (methylethylene) group, a butylene (tetramethylene) group, an isobutylene (methyltrimethylene) group, a tert-butylene (dimethylethylene) group, a pentamethylene group, a hexylene (hexamethylene) group, a heptamethylene group, an octamethylene group, a nonamethylene group, a decamethylene group, and a dodecamethylene group; cycloalkylene groups such as a 1,3- or 1,2-cyclopentylene group or a 1,4-cyclohexylene group; and arylene groups such as a phenylene group, a tolylene group, a xylylene group, and an α- or β-naphthylene group. Among these, alkylene groups such as propylene (trimethylene) group and hexylene (hexamethylene) group are preferred, with propylene (trimethylene) group being particularly preferred.

[0052] R ２ and R ３ are independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms. The alkyl group having 1 to 10 carbon atoms may be linear, cyclic, or branched. Specific examples thereof include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and isobornyl. Specific examples of aryl groups having 6 to 10 carbon atoms include phenyl, tolyl, xylyl, α-naphthyl, and β-naphthyl. Some or all of the hydrogen atoms in these groups may be substituted with alkyl groups, aryl groups, halogen atoms such as F, Cl, and Br, or cyano groups. Among these, R ２ and R ３ As the alkyl group, a methyl group, an ethyl group, a vinyl group, or a phenyl group is preferred, and in terms of reactivity and cost, a methyl group or a vinyl group is more preferred.

[0053] n is a number from 0 to 50, preferably a number from 0 to 20, and particularly preferably a number from 0 to 5. m is a number from 0 to 3, and particularly preferably 3, and l is 1 or 2, and particularly preferably 2.

[0054] The epoxy prepolymer is preferably a reaction product of a bifunctional epoxy compound (diglycidyl compound) represented by the general formula (2) described below, an aminoalkylsilane compound represented by the general formula (3), and a hydrolyzable organosilane compound (alkylalkoxysilane) having no amino group or mercapto group represented by the general formula (4).

[0055] The weight-average molecular weight of the epoxy prepolymer is preferably 500 to 100,000, and more preferably 1,000 to 5,000. The weight-average molecular weight of the epoxy prepolymer can be determined as a polystyrene-equivalent weight-average molecular weight by gel permeation chromatography (GPC) analysis using, for example, tetrahydrofuran as a developing solvent.

[0056] Examples of preferred epoxy prepolymers include the following: wherein Me represents a methyl group.

[0057] [Method for Producing Epoxy Prepolymer] The method for producing the above-mentioned epoxy prepolymer is characterized by mixing and reacting (B2a) a bifunctional epoxy compound (diglycidyl compound) represented by the following general formula (2), (B2b) an aminoalkylsilane compound represented by the following general formula (3), and (B2c) a hydrolyzable organosilane compound (alkylalkoxysilane) having no amino group or mercapto group represented by the following general formula (4):

[0058] (In formula (2), X is the same as X in average composition formula (1).)

[0059] (In formula (3), R １ , R ２ , R ３ and m are R in the average composition formula (1), １ , R ２, R ３ and m.)

[0060] (In formula (4), R ２ , R ３ are R in the average composition formula (1), ２ , R ３ and l' is 2 or 3.

[0061] Examples of the diglycidyl compound represented by formula (2) of component (B2a) include 1,2-cyclohexanedicarboxylate diglycidyl, neopentyl glycol diglycidyl, bisphenol A diglycidyl, bisphenol F diglycidyl, bisphenol AF diglycidyl, and 2,2-bis(4-glycidyloxyphenyl)propane. From the standpoints of cost and solubility in solvents, bisphenol A diglycidyl is preferred. Furthermore, as component (B2a), hydrolyzed condensation polymers (organosiloxane oligomers having two glycidyl groups in the molecule) of hydrolyzable glycidyl compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxysilane, and 3-glycidoxypropyldiethoxysilane may also be used.

[0062] Examples of the aminoalkylsilane compound represented by formula (3) of component (B2b) include (hydrolyzable) organosilane compounds (silane coupling agents) having an alkyl group substituted with a primary amino group in the molecule and 0 to 3 hydrolyzable groups such as alkoxy groups bonded to silicon atoms in the molecule, such as γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane. In particular, γ-aminopropyltrimethoxysilane is preferred, as it exhibits excellent film-forming and adhesive properties when it contains a methoxy group. It is also possible to use a hydrolysis condensation polymer of the aminoalkylsilane compound represented by formula (3) (an organosiloxane oligomer having an alkyl group substituted with a primary amino group in the molecule and residual hydrolyzable groups such as alkoxy groups) as component (B2b).

[0063] Examples of the alkylalkoxysilane represented by formula (4) of the component (B2c) include methyltrimethoxysilane, octyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, and methyltriethoxysilane. From the standpoints of cost and reactivity, methyltrimethoxysilane or vinyltrimethoxysilane is preferred.

[0064] The amount of component (B2b) added is preferably 0.1 to 1.0 mol, and more preferably 0.1 to 0.6 mol, per 1 mol of the polyfunctional epoxy compound (diglycidyl compound) represented by general formula (2) (B2a).

[0065] The amount of component (B2c) added is preferably 1.0 to 10.0 moles, and more preferably 1.0 to 5.0 moles, per mole of the polyfunctional epoxy compound (diglycidyl compound) represented by general formula (2) (B2a).

[0066] In the method for producing an epoxy prepolymer, the temperature at which (B2a) the diglycidyl compound represented by the general formula (2), (B2b) the aminoalkylsilane represented by the general formula (3), and (B2c) the alkylalkoxysilane represented by the general formula (4) are mixed and reacted is 10 to 90°C, preferably 20 to 70°C. If the temperature is outside this range, the reaction may be significantly slowed or the viscosity may increase significantly, making it difficult to recover the reaction product. The reaction time for mixing and reacting is preferably 2 hours to 5 days, more preferably 8 hours to 3 days.

[0067] According to the method for producing an epoxy prepolymer, a reaction mixture (side-chain alkoxysilane-containing epoxy prepolymer) can be obtained that is liquid at room temperature (23°C ± 15°C) or soluble in the organic solvent (C) used in the present invention, namely, aromatic hydrocarbon solvents, alcohol solvents, ketone solvents, ether solvents, ester solvents, and paraffin solvents.

[0068] The blending amount of component (B) is preferably 1 to 70 mass %, more preferably 5 to 50 mass %, of the total mass of components (A), (B), and (C).Within this range, the primer layer provided between the porous substrate and the silicone resin layer can exhibit good adhesion.

[0069] - Component (C) - The organic solvent for component (C) may be any organic solvent that dissolves the components in the primer composition in any desired proportion and is volatile at the same time, and from the standpoint of handling, it preferably has a flash point of -40°C or higher, a boiling point of 41°C or higher, and an ignition point of 101°C or higher, and more preferably has a flash point of -30°C or higher, a boiling point of 60°C or higher, and an ignition point of 200°C or higher. The flash point here is a value measured by the rapid equilibrium closed-loop method described in JIS-K2265-2:2007, the boiling point is a value at 1 atmosphere (1013 hPa), and the ignition point is the lower limit of the temperature at which the organic solvent instantly ignites when dropped into a container heated to a constant temperature.

[0070] Specific examples of component (C) include aromatic hydrocarbon solvents such as benzene, toluene, and xylene; alcohol solvents such as methanol, ethanol, isopropyl alcohol, and ethylene glycol monomethyl; ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; ester solvents such as ligroin, ethyl acetate, butyl acetate, and isobutyl acetate; and paraffin solvents such as hexane and cyclohexane, which can be used alone or in combination of two or more. Among these, aromatic hydrocarbon solvents, paraffin solvents, and ester solvents are preferred, and toluene, hexane, ethyl acetate, butyl acetate, and isobutyl acetate are particularly preferred.

[0071] The incorporation of component (C) allows adjustment of the workability of the primer composition during application and drying. The amount of component (C) is not particularly limited, but is 5 to 1,000 parts by mass, preferably 5 to 100 parts by mass, per 10 parts by mass of component (B). Within this range, a uniform coating film of the primer composition can be formed, and unevenness on the coating film surface can be suppressed. When components (A), (B), etc. are added as a solution, the amount of component (C) refers to the total amount in the composition, including the solvent in the solution.

[0072] -Component (D)- The primer composition of the present invention may further contain, as an optional component (D), a hydrolyzable organosilane compound and / or a partial hydrolyzed condensate thereof, for the purpose of improving the storage stability of the composition.

[0073] The hydrolyzable organosilane compound and / or its partial hydrolysis condensate of component (D) may be the same as the hydrolyzable organosilane compound and / or its partial hydrolysis condensate that does not have an amino group or a mercapto group in component (B), and examples thereof include ketoxime group-containing silanes such as methyltris(methylethylketoxime)silane, vinyltris(methylethylketoxime)silane, phenyltris(methylethylketoxime)silane, and methyltris(dimethylketoxime)silane; methyltrimethoxysilane, octyltrimethoxysilane, dimethyldimethoxysilane, and the like. Examples include alkoxysilanes such as methoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, and 2-ethylhexyl α-(dimethoxymethylsilyl)propionate; isopropenoxy group-containing silanes such as methyltriisopropenoxysilane, ethyltriisopropenoxysilane, vinyltriisopropenoxysilane, and phenyltriisopropenoxysilane; acetoxysilanes such as methyltriacetoxysilane, ethyltriacetoxysilane, and vinyltriacetoxysilane; and partial hydrolysis condensates of these silanes. These may be used alone or in combination of two or more.

[0074] The amount of component (D) is not particularly limited, but is generally 0.01 to 100 parts by mass, preferably 0.1 to 10 parts by mass, per 10 parts by mass of component (B). This range ensures that there is no effect on the preparation process and that good shelf life can be achieved. Note that, when a hydrolyzable organosilane compound and / or its partial hydrolysis condensate that does not have an amino group or a mercapto group is added to components (B1) and (B2), component (D) need not be added.

[0075] In addition to the components (A) to (D) described above, the primer composition of the present invention may further contain at least one known additive selected from the group consisting of pigments, dyes, antioxidants, antioxidants, adhesion promoters, antistatic agents, and flame retardants such as antimony oxide and chlorinated paraffins, within the scope of the present invention. Furthermore, mildew inhibitors, antibacterial agents, etc. may also be added within the scope of the present invention.

[0076] The primer composition of the present invention is preferably used for bonding a cured product of a room-temperature condensation-curable silicone rubber composition or an addition-curable silicone rubber composition to a porous substrate. That is, it can be suitably used to improve the adhesion between a porous substrate and a silicone resin consisting of a cured product (silicone rubber cured product) of a room-temperature condensation-curable silicone rubber composition or an addition-curable silicone rubber composition, and is particularly suitable for improving adhesion (water-resistant adhesion) when the application site is submerged (submerged). In the present invention, examples of porous substrates include wood, synthetic wood, and cured products of hydraulic compositions (cured mortar, cured concrete, cured cement), but wood is preferred, and examples of wood materials include cypress, cedar, and pine. Furthermore, the porous substrate may be treated as desired to improve the durability, weather resistance, and design of the substrate.

[0077] [Method for bonding silicone resin to porous substrate] The method for bonding a silicone resin (cured silicone rubber layer) to a porous substrate according to the present invention is characterized by comprising the steps of: applying the primer composition of the present invention described above to the surface of a porous substrate to form a primer layer; and then applying and curing a room-temperature condensation-curable silicone rubber composition or an addition-curable silicone rubber composition to the surface of the primer layer to form a silicone resin layer made of cured silicone rubber.

[0078] As a method for adhering the silicone resin of the present invention (cured silicone rubber layer) to a porous substrate, for example, the primer composition of the present invention may be applied to the surface of the porous substrate (coating with a brush or nonwoven fabric, followed by air drying (curing) at room temperature (23°C ± 15°C) for 30 minutes to 12 hours, preferably 30 minutes to 2 hours (also referred to as primer treatment)) to form a primer layer, and then a silicone rubber composition selected from a room temperature condensation curing silicone rubber composition and an addition curing silicone rubber composition is applied to the outer surface of the primer layer to form the silicone rubber composition layer, and the silicone rubber composition layer is cured (i.e., a room temperature condensation curing silicone rubber composition is applied and the composition is cured at room temperature (23°C ± 15°C), or an addition curing silicone rubber composition is applied and the composition is cured at room temperature (23°C ± 15°C) or by heating (50 to 100°C)), thereby forming a silicone resin consisting of the cured silicone rubber, thereby adhering the silicone resin to the porous substrate.

[0079] According to the present invention, the surface of a porous substrate such as wood is primed with the primer composition of the present invention, and then a silicone rubber composition selected from a room-temperature condensation-curing silicone rubber composition and an addition-curing silicone rubber composition is applied, and the applied film is cured. This allows the applied (coated and cured) area to exhibit good adhesion even after immersion in water, and in particular improves the water-resistant adhesion between the silicone resin and the porous substrate.

[0080] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Note that the number of moles in the following examples is when "parts by mass" is "g." Room temperature refers to 23°C.

[0081] Synthesis Example 1: Preparation of Acrylic Copolymer 1 To 47 parts by mass of ethyl acetate, 34 parts by mass of methyl methacrylate and 1.8 parts by mass of 3-methacryloxypropyltrimethoxysilane were added, mixed under nitrogen aeration, and heated to a temperature of 80°C. Next, 0.1 parts by mass of 2,2'-azobis(2-methylbutyronitrile) was added and mixed to dissolve. The mixture was further aged at 80°C for 3 hours and then cooled to 40°C or below. After cooling, 0.02 parts by mass of 4-methoxyphenol was added to stop the reaction, and a colorless, transparent acrylic copolymer solution 1 was obtained.

[0082] Synthesis Example 2: Preparation of Acrylic Polymer 2 Acrylic polymer solution 2 was obtained in the same manner as in Synthesis Example 1, except that 1.8 parts by mass of 3-methacryloxypropyltrimethoxysilane was not used.

[0083] Synthesis Example 3 Preparation 1 of Reaction Mixture of Polyfunctional Isocyanate Compound and Mercaptoalkylsilane To 53 parts by mass of ethyl acetate, 18 parts by mass of N3200XPM (aliphatic polyisocyanate solution (containing 73% by mass of aliphatic polyisocyanate); manufactured by Godo Chemical Co., Ltd.), 30 parts by mass (0.15 mol) of γ-mercaptopropyltrimethoxysilane, and 0.1 parts by mass of tin 2-ethylhexanoate were added, and the mixture was stirred at room temperature for 40 minutes in a moisture-blocked environment, to obtain Reaction Mixture 1.

[0084] Synthesis Example 4 Preparation 2 of Reaction Mixture of Polyfunctional Isocyanate Compound and Mercaptoalkylsilane To 28 parts by mass of toluene, 17 parts by mass (0.10 mol) of tolylene diisocyanate, 39 parts by mass (0.20 mol) of γ-mercaptopropyltrimethoxysilane, and 0.2 parts by mass of tin 2-ethylhexanoate were added, and the mixture was stirred at room temperature for 1 hour in a moisture-blocked environment, to obtain reaction mixture 2.

[0085] Synthesis Example 5 Preparation 1 of Reaction Mixture of Polyfunctional Epoxy Compound and Aminoalkylsilane To 51 parts by mass (0.15 mol) of 2,2-bis(4-glycidyloxyphenyl)propane, 9.0 parts by mass (0.05 mol) of γ-aminopropyltrimethoxysilane and 27 parts by mass (0.20 mol) of methyltrimethoxysilane were added, and the mixture was refluxed in a reflux condenser under moisture-blocking conditions, and stirred at 60° C. for 8 hours to obtain Reaction Mixture 3.

[0086] Synthesis Example 6 Preparation 2 of Reaction Mixture of Polyfunctional Epoxy Compound and Aminoalkylsilane To 34 parts by mass (0.10 mol) of 2,2-bis(4-glycidyloxyphenyl)propane, 12 parts by mass (0.05 mol) of N-[3-(trimethoxysilyl)propyl]butan-1-amine and 7.5 parts by mass (0.06 mol) of methyltrimethoxysilane were added, and the mixture was refluxed in a reflux condenser under moisture protection and stirred at 60° C. for 8 hours to obtain Reaction Mixture 4.

[0087] Example 1 To 27 parts by mass of [acrylic copolymer solution 1] obtained in Synthesis Example 1, 18 parts by mass of [reaction mixture 1] obtained in Synthesis Example 3, 27 parts by mass of toluene, 7.2 parts by mass of γ-mercaptopropyltrimethoxysilane as an adhesion promoter, and 23 parts by mass of Dismodur HL (a solution of a compound (isocyanurate) formed by an addition reaction of triresin isocyanate (TDI) and hexamethylene diisocyanate (HDI); manufactured by Covestro), were added, and the mixture was uniformly mixed at room temperature for 1 hour in a moisture-protected environment, to obtain Composition 1. The obtained composition 1 was applied uniformly with a brush to the main surface of a porous substrate, a wooden board (cypress) (dimensions (length × width × length): 50 mm × 50 mm × 25 mm), and left to stand for 30 minutes under conditions of a temperature of 23°C and a humidity of 50% RH to form a primer layer. After that, a dealcoholization-type (room temperature condensation curing type) two-component silicone sealant (SEALANT-FC-295SG: manufactured by Shin-Etsu Chemical Co., Ltd.) was applied in the form of a bead (diameter 10 mm, length 50 mm) to the surface (on the primer layer) of the wooden board that had been coated with composition 1, to prepare a test piece for evaluating adhesion.

[0088] [Example 2] 18 parts by mass of [Reaction mixture 2] obtained in Synthesis Example 4 and 6.0 parts by mass of toluene were added to 10 parts by mass of [Acrylic copolymer solution 1] obtained in Synthesis Example 1, and the mixture was mixed uniformly at room temperature for 30 minutes in a moisture-protected environment to obtain Composition 2. Using the obtained Composition 2, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0089] [Example 3] 18 parts by mass of [Reaction mixture 3] obtained in Synthesis Example 5 and 18 parts by mass of toluene were added to 15 parts by mass of [Acrylic copolymer solution 1] obtained in Synthesis Example 1, and the mixture was mixed uniformly at room temperature for 30 minutes in a moisture-protected environment to obtain Composition 3. Using the obtained Composition 3, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0090] [Example 4] 18 parts by mass of [Reaction mixture 4] obtained in Synthesis Example 6 and 18 parts by mass of toluene were added to 15 parts by mass of [Acrylic copolymer solution 1] obtained in Synthesis Example 1, and the mixture was mixed uniformly at room temperature for 30 minutes in a moisture-protected environment to obtain Composition 4. Using the obtained Composition 4, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0091] Comparative Example 1 Test pieces for evaluating adhesion were prepared in the same manner as in Example 1, except that no primer composition was used (i.e., the two-component silicone sealant was applied directly to the wood without forming a primer layer).

[0092] Comparative Example 2 Except for not using 27 parts by mass of [acrylic copolymer solution 1], 7.2 parts by mass of γ-mercaptopropyltrimethoxysilane, and 23 parts by mass of Dismodur HL, the procedure of Example 1 was repeated, i.e., 18 parts by mass of [reaction mixture 1] and 27 parts by mass of toluene were added and mixed uniformly at room temperature for 1 hour in a moisture-protected environment to obtain Composition 5. Using the obtained Composition 5, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0093] Comparative Example 3 Composition 6 was obtained in the same manner as in Example 2, except that 10 parts by mass of [Acrylic Copolymer Solution 1] was not added. Using the obtained composition 6, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0094] Comparative Example 4 Composition 7 was obtained in the same manner as in Example 3, except that 15 parts by mass of [Acrylic Copolymer Solution 1] was not added. Using the obtained composition 7, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0095] Comparative Example 5 Composition 8 was obtained in the same manner as in Example 2, except that 10 parts by mass of [Acrylic Polymer Solution 2] obtained in Synthesis Example 2 was added instead of 10 parts by mass of [Acrylic Copolymer Solution 1] in Example 2. Using the obtained composition 8, a test piece for evaluating adhesion was prepared in the same manner as in Example 1.

[0096] [Evaluation of Adhesion] Using the test pieces for evaluating adhesion prepared in Examples 1 to 4 and Comparative Examples 1 to 5, the adhesion to wood (cypress) was evaluated by the following method.

[0097] [Initial Adhesion] The test pieces for adhesiveness evaluation were aged for 7 days under conditions of 23°C and 50% RH, after which the bead-shaped silicone rubber cured product of the silicone sealant was cut with a knife and the cut portion was manually peeled off (the bead-shaped silicone rubber cured product was pinched with fingers and pulled in the direction of peeling from the wood), and the peeling state was observed to evaluate the state of the adhesive interface between the wood (adherend including the primer layer) and the bead-shaped silicone rubber cured product. The evaluation was based on the following criteria: if the area of ​​the primer layer that had cohesively failed on the peeled surface of the bead-shaped silicone rubber cured product (sealant) was 90% or more, it was rated as "Good," if it was 50% or more but less than 90%, it was rated as "Average," and if it was less than 50%, it was rated as "Poor." The initial adhesion test results for each primer composition are shown in Table 1.

[0098] [Water-resistant adhesion] After aging for 7 days under conditions of a temperature of 23°C and a humidity of 50% RH, the specimens were further immersed in warm water at 50°C for 7 days, dried for 1 to 3 hours, and then evaluated in the same manner as in the test for initial adhesion. The test results for water-resistant adhesion when each primer composition was used are shown in Table 1.

[0099]

[0100] From the results in Table 1, Examples 1 to 4 showed not only good initial adhesion but also good adhesion after immersion in water (water-resistant adhesion). On the other hand, although Comparative Examples 1 to 5 showed good initial adhesion, Comparative Example 4 was rated as "△" for water-resistant adhesion, and Comparative Examples 1, 2, 3, and 5 were rated as "×".

[0101] Synthesis Example 7 Synthesis of Epoxy Prepolymer 1 In a 500 ml separable flask equipped with a stirrer, a reflux condenser, and a thermometer, 68.08 g (0.2 mol) of bisphenol A diglycidyl ether, 17.93 g (0.1 mol) of γ-aminopropyltrimethoxysilane, and 29.65 g (0.2 mol) of vinyltrimethoxysilane were placed, heated to 60° C., and stirred for 3 days to obtain a colorless, transparent liquid (epoxy prepolymer 1) composed of a compound represented by the following formula (11).

[0102] The weight-average molecular weight of the obtained epoxy prepolymer was confirmed to be 2808 by GPC measurement. In this example, the weight-average molecular weight is a value analyzed by GPC (gel permeation chromatography) using polystyrene as a standard substance under the following conditions. [Measurement conditions] Developing solvent: tetrahydrofuran (THF) Flow rate: 0.35 ml / min Column: Multipore HZ-H x 4 (manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 10 μL (THF solution with a concentration of 0.2% by mass)

[0103] Synthesis Example 8: Synthesis of epoxy prepolymer 2 A 500 ml separable flask equipped with a stirrer, reflux condenser, and thermometer was charged with 43.26 g (0.2 mol) of neopentyl glycol diglycidyl ether, 17.93 g (0.1 mol) of γ-aminopropyltrimethoxysilane, and 29.65 g (0.2 mol) of vinyltrimethoxysilane, and the mixture was heated to 60° C. and stirred for 3 days to obtain a colorless, transparent liquid (epoxy prepolymer 2) composed of a compound represented by the following formula (12). The weight-average molecular weight of the obtained epoxy prepolymer was confirmed to be 2020 by GPC measurement.

[0104] Synthesis Example 9: Preparation of epoxy prepolymer 3 A 500 ml separable flask equipped with a stirrer, a reflux condenser, and a thermometer was charged with 34.84 g (0.2 mol) of ethylene glycol diglycidyl ether, 17.93 g (0.1 mol) of γ-aminopropyltrimethoxysilane, and 29.65 g (0.2 mol) of vinyltrimethoxysilane, and the mixture was heated to 60° C. and stirred for 3 days to obtain a colorless, transparent liquid (epoxy prepolymer 3) composed of a compound represented by the following formula (13): The weight-average molecular weight of the obtained epoxy prepolymer was confirmed to be 2,090 by GPC measurement.

[0105] Example 5 Forty parts by mass of the acrylic copolymer solution 1 obtained in Synthesis Example 1, 30 parts by mass of the epoxy prepolymer 1 obtained in Synthesis Example 7, and 30 parts by mass of toluene were uniformly mixed at room temperature for 1 hour under moisture-shielded conditions to obtain Composition 9. The resulting composition 9 was uniformly applied with a brush to the main surface of a porous substrate, a plank of wood (cypress) (main surface dimensions: 120 mm × 120 mm), and left to stand for 30 minutes under conditions of a temperature of 23 ° C. and a humidity of 50% RH to form a primer layer. After that, a dealcohol-curing (room temperature condensation-curing) two-component silicone sealant (SEALANT-FC-295SG: manufactured by Shin-Etsu Chemical Co., Ltd.) was applied in the form of a bead (diameter 10 mm, length 50 mm) to the surface (on the primer layer) of the wood to which Composition 9 had been applied, and a test piece for evaluating adhesion was prepared.

[0106] Example 6 A test piece for evaluating adhesiveness was prepared in the same manner as in Example 5, except that epoxy prepolymer 2 was used instead of epoxy prepolymer 1.

[0107] Example 7 A test piece for evaluating adhesiveness was prepared in the same manner as in Example 5, except that Epoxy Prepolymer 3 was used instead of Epoxy Prepolymer 1.

[0108] Comparative Example 6 Test pieces for evaluating adhesion were prepared in the same manner as in Example 5, except that no primer composition was used (i.e., the two-component silicone sealant was applied directly to the wood without forming a primer layer).

[0109] [Evaluation of Adhesion] Using the test pieces for adhesiveness evaluation prepared in Examples 5 to 7 and Comparative Example 6, the adhesiveness to wood (cypress) was evaluated by the following method.

[0110] [Initial Adhesion] The test pieces for evaluating adhesion were aged for 7 days under conditions of 23°C and 50% RH, after which the bead-shaped silicone rubber cured product of the silicone sealant was cut with a knife and the cut portion was manually peeled off (the bead-shaped silicone rubber cured product was pinched with fingers and pulled in the direction of peeling from the wood), and the peeling state was observed to evaluate the state of the adhesive interface between the wood (adherend including the primer layer) and the bead-shaped silicone rubber cured product. The evaluation was based on the following criteria: "Good" indicates that the percentage of the area of ​​cohesive failure on the peeled surface of the bead-shaped silicone rubber cured product (sealant) was 80% or more; "Average" indicates that the percentage was 50% or more but less than 80%; and "Poor" indicates that the percentage was less than 50%. The initial adhesion test results for each primer composition are shown in Table 2.

[0111] [Water-resistant adhesion] After aging for 7 days under conditions of a temperature of 23°C and a humidity of 50% RH, the specimens were further immersed in water at 50°C for 7 days, thoroughly dried, and then evaluated in the same manner as in the test for initial adhesion. The test results for water-resistant adhesion when each primer composition was used are shown in Table 2.

[0112]

[0113] From the results in Table 2, Examples 5 to 7 showed good adhesion not only in the initial stage but also after immersion in water (water-resistant adhesion).

Claims

1. A primer composition for porous substrates, comprising: (A) a (meth)acrylic copolymer having an alkoxysilyl group; (B) an adhesion improver consisting of a reaction mixture of the following components (B1) and / or (B2); (B1) a reaction mixture of a polyfunctional isocyanate compound and a mercaptoalkylsilane compound; (B2) a reaction mixture of a polyfunctional epoxy compound and an aminoalkylsilane compound; and (C) an organic solvent.

2. The primer composition according to claim 1, wherein the component (B1) is a reaction mixture with a hydrolyzable organosilane compound having no amino group or mercapto group and / or a partial hydrolysis condensate thereof.

3. The primer composition according to claim 1, wherein the component (B2) is a reaction mixture of a hydrolyzable organosilane compound having no amino group or no mercapto group and / or a partial hydrolysis condensate thereof.

4. The primer composition according to claim 1, wherein the component (B2) comprises an epoxy prepolymer represented by the following average composition formula (1): (In formula (1), X is independently a divalent hydrocarbon group having 1 to 31 carbon atoms which may contain an oxygen atom, a nitrogen atom, or a sulfur atom; R １ are independently an alkylene group having 3 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and R ２ and R ３ are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, l is independently 1 or 2, m is independently a number from 0 to 3, and n is a number from 0 to 50.

5. The primer composition according to claim 1, wherein the component (B2) comprises a reaction product of a polyfunctional epoxy compound represented by the following general formula (2), an aminoalkylsilane compound represented by the general formula (3), and a hydrolyzable organosilane compound having no amino group or mercapto group represented by the general formula (4): (In formula (2), X represents a divalent hydrocarbon group having 1 to 31 carbon atoms and optionally containing an oxygen atom, a nitrogen atom, or a sulfur atom, and having at least one of an alkylene group which may have a branched structure, a monocyclic structure, and a polycyclic structure.) (In formula (3), R １ is an alkylene group having 3 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and R ２ and R ３ are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, and m is a number from 0 to 3. (In formula (4), R ２ and R ３ are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, and l' is 2 or 3.

6. The primer composition according to claim 5, wherein the aminoalkylsilane compound is γ-aminopropyltrimethoxysilane or γ-aminopropyltriethoxysilane.

7. The primer composition according to claim 1, further comprising (D) a hydrolyzable organosilane compound and / or a partial hydrolysis condensate thereof.

8. The primer composition according to claim 1, wherein the (meth)acrylic copolymer of component (A) is a copolymer of a (meth)acrylic acid ester monomer having an alkoxysilyl group and a (meth)acrylic acid ester monomer not having an alkoxysilyl group.

9. The primer composition according to claim 8, wherein the content of the (meth)acrylic acid ester monomer having an alkoxysilyl group in the total monomer components of component (A) is 1 to 30 mass %.

10. A primer composition according to claim 1, wherein the component (C) is any one or a mixture of two or more selected from aromatic hydrocarbon solvents, alcohol solvents, ketone solvents, ether solvents, ester solvents and paraffin solvents.

11. The primer composition according to claim 1, wherein component (C) has a flash point of -40°C or higher, a boiling point of 41°C or higher, and an ignition point of 101°C or higher.

12. The primer composition according to claim 1, which is used to bond a cured product of a room temperature condensation curing type silicone rubber composition or an addition curing type silicone rubber composition to a porous substrate.

13. The primer composition according to claim 1, which is used to improve water-resistant adhesion.

14. The primer composition of claim 1, wherein the porous substrate is made of wood.

15. A method for adhering a silicone resin to a porous substrate, comprising the steps of: applying a primer composition according to any one of claims 1 to 14 to the surface of the porous substrate to form a primer layer; and then applying and curing a room-temperature condensation-curing silicone rubber composition or an addition-curing silicone rubber composition to the surface of the primer layer to form a silicone resin layer made of a cured silicone rubber.

16. The bonding method according to claim 15, which improves the water-resistant adhesion between a silicone resin and a porous substrate.

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