JP6535916B2 - Resin composition and coating structure - Google Patents

Description

  The present invention relates to a resin composition and a painted structure.

  The member which formed the metal plating layer on the surface of the base material is used for exterior parts, such as a car and a motorcycle. As surface treatment of a metal plating layer, the process which forms the coating film for the purpose of provision of the characteristic design which harnessed metal luster, and protection of a metal plating layer is performed.

However, there has been a problem that the peeling of the coating film is enlarged due to blemishes (chipping) due to rebounding of pebbles in operation, snow melting agents in cold regions, and the like. From the situation where the expansion of peeling is triggered by a flaw reaching the metal plating layer, a coating film excellent in adhesion and chipping resistance is required.
In order to improve adhesion of such a coating film and chipping resistance, forming a coating film of a primer layer formed on a metal plating layer and a two-layer finish coating of a top coat layer formed on the primer layer Has been proposed.

  For example, Patent Document 1 proposes a method of forming a primer layer with an epoxy resin composition and forming a top coat layer containing a urethane resin on the primer layer (Patent Document 1). According to Patent Document 1, the water resistance and the chipping resistance can be improved.

JP 2011-137145 A

Such a coating film is required to be excellent in chipping resistance, water resistance, adhesion, weather resistance and appearance as well. However, Patent Document 1 does not consider such an effect.
The present invention has been made in view of the above circumstances, and provides a resin composition in which the resulting coated structure is excellent in adhesion, weatherability, water resistance, chipping resistance, and appearance, and adhesion, weatherability. It is an object of the present invention to provide a painted structure having excellent properties, water resistance, chipping resistance and appearance.

［式（ａ１）中、Ｒ^ａ１は水素原子又は炭素数１〜５のアルキル基であり、Ｒ^ａ２は、炭素数１０〜２０の１価の炭化水素基であり、式（ａ２）中、Ｒ^ｂ１は水素原子又は炭素数１〜５のアルキル基であり、−Ｘ^ｂ１ＯＨは、−（ＣＨ_２）_ｍ−Ｏ−（Ｘ^ｂ２Ｏ）_ｎ−Ｈであり、ｍは２〜１０の数であり、ｎは１〜１０の数であり、Ｘ^ｂ２は−Ｃ（＝Ｏ）−Ｘ^ｂ３−であり、Ｘ^ｂ３は炭素数１〜１０の２価の炭化水素基である。］
［２］前記構成単位（ａ２）の割合が、前記アクリル樹脂（Ａ）を構成する全構成単位の総モル数に対し、３０モル％以下である、［１］に記載の樹脂組成物。
［３］さらにポリオール（Ｄ）を含有し、
前記ポリオール（Ｄ）の重量平均分子量が５００〜５００００であり、
前記ポリオール（Ｄ）の水酸基価が２０〜２００ｍｇＫＯＨ／ｇである、［１］又は［２］に記載の樹脂組成物。
［４］金属めっき層と、前記金属めっき層の上に位置し、［１］〜［３］のいずれか一項に記載の樹脂組成物から形成されるプライマー層と、前記プライマー層の上に位置するトップコート層とを含む塗装構造体。
［５］前記トップコート層はポリオール（Ｇ）を含み、
前記ポリオール（Ｇ）は重量平均分子量が７０００〜４００００であり、水酸基価が２５〜８０ｍｇＫＯＨ／ｇである、［４］に記載の塗装構造体。
As a result of intensive studies, the present inventors have found that the following resin composition and coating structure can solve the above problems.
That is, the present invention has the following aspects.
[1] a structural unit (a1) represented by the following formula (a1),
An acrylic resin (A) having a structural unit (a2) represented by the following formula (a2),
The hydroxyl value of the acrylic resin (A) is 30 to 50 mg KOH / g,
The glass transition point of the acrylic resin (A) is -30 ° C. or less,
The proportion of the structural unit (a1) is, relative to the total number of moles of all the structural units that constitute the acrylic resin (A), the Ri der 16 mol% or more,
The proportion of the structural unit (a2) is, relative to the total number of moles of all the structural units that constitute the acrylic resin (A), the Ru der least 12 mol%, the resin composition.

[In the formula (a1), R ^a1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ^a2 is a monovalent hydrocarbon group having 10 to 20 carbon atoms, and in the formula (a2), R ^b1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, -X ^b1 OH is-(CH ₂ ) _m -O- (X ^b2 O) _n -H, m is a number of 2 to 10 And n is a number of 1 to 10, X ^b2 is -C (= O)-X ^b3- , and X ^b3 is a divalent hydrocarbon group having 1 to 10 carbon atoms. ]
[2] The resin composition according to [1], wherein the proportion of the structural unit (a2) is 30 mol% or less based on the total number of moles of all the structural units constituting the acrylic resin (A).
[3] It further contains a polyol (D),
The weight average molecular weight of the polyol (D) is 500 to 50000,
The resin composition as described in [1] or [2] whose hydroxyl value of the said polyol (D) is 20-200 mgKOH / g.
[4] A metal plating layer, a primer layer located on the metal plating layer and formed from the resin composition according to any one of [1] to [3], and the primer layer A painted structure comprising a located top coat layer.
[5] The top coat layer contains a polyol (G),
The coated structure according to [4], wherein the polyol (G) has a weight average molecular weight of 7,000 to 40,000 and a hydroxyl value of 25 to 80 mg KOH / g.

  ADVANTAGE OF THE INVENTION According to this invention, the coating structure obtained can provide the resin composition which is excellent in adhesiveness, a weather resistance, water resistance, chipping resistance, and an appearance, and adhesiveness, a weather resistance, water resistance, a chipping resistance. It is possible to provide a painted structure excellent in the properties and appearance.

It is sectional drawing of the coating structure of this invention.

«Resin composition»
The resin composition of the present invention is characterized by containing an acrylic resin (A) having a structural unit (a1) represented by the formula (a1) and a structural unit (a2) represented by the formula (a2) I assume.
It is preferable that the resin composition of this invention is for primer layer formation formed in the surface of a metal plating layer.
In the present specification, “constituent unit” means a monomer unit (monomer unit) constituting a polymer compound (resin, polymer, copolymer). Further, “(meth) acrylate” means one or both of an acrylate having a hydrogen atom bonded to the α-position and a methacrylate having a methyl group bonded to the α-position. The term "(meth) acrylic acid" means one or both of acrylic acid having a hydrogen atom bonded to the alpha position and methacrylic acid having a methyl group bonded to the alpha position.

<Constituent unit (a1)>
The structural unit (a1) is a structural unit represented by the following formula (a1).

［式（ａ１）中、Ｒ^ａ１は水素原子又は炭素数１〜５のアルキル基であり、Ｒ^ａ２は、炭素数１０〜２０の１価の炭化水素基である。］

[In formula (a1), R ^a1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ^a2 is a monovalent hydrocarbon group having 10 to 20 carbon atoms. ]

The structural unit (a1) is a structural unit derived from a monomer represented by the following formula (a1 ′).
CH ₂ = C (R ^a1 ) COOR ^a2 (a1 ')
[In formula (A '), R ^a1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ^a2 is a monovalent hydrocarbon group having 10 to 20 carbon atoms. ]

R ^a1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. As a C1-C5 alkyl group, a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group are mentioned. Among them, a hydrogen atom or a methyl group is preferable.
R ^a2 is a C 10-20 monovalent hydrocarbon group. R ^a2 may be linear, branched or cyclic, and is preferably linear or branched. As a monovalent hydrocarbon group, an alkyl group is preferable.
As the structural unit (a1), one type of structural unit may be used alone, or two or more types may be used in combination.

  The proportion of the structural unit (a1) is 16 mol% or more, preferably 16 to 71 mol%, and more preferably 20 to 30 mol% with respect to the total number of moles of all structural units constituting the acrylic resin (A). . By setting the ratio of the structural unit (a1) within the above-mentioned numerical range, it is possible to impart good initial adhesion and water adhesion resistance.

<Constituent unit (a2)>
The structural unit (a2) is a structural unit represented by the following formula (a2).

［式（ａ２）中、Ｒ^ｂ１は水素原子又は炭素数１〜５のアルキル基であり、Ｘ^ｂ１は炭素数３〜５０の２価の連結基である。］

[In Formula (a2), R ^b1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and X ^b1 is a divalent linking group having 3 to 50 carbon atoms. ]

The structural unit (a2) is a structural unit derived from a monomer represented by the following formula (a2 ′).
_{^{CH 2 = C (R b1)}} COOX b1 -OH ··· (a2 ')
[In Formula (a2 ′), R ^b1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and X ^b1 is a divalent linking group having 3 to 50 carbon atoms. ]

R ^b1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. As a C1-C5 alkyl group, a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group are mentioned. Among them, a hydrogen atom or a methyl group is preferable.
X ^b1 is a C3-C50 divalent linking group. The number of carbon atoms of X ^b1 is preferably 10 to 40, 20 to 35 is more preferable. Examples of the divalent linking group include a divalent hydrocarbon group, a divalent linking group containing a hetero atom, and the like.
The hydrocarbon group as the divalent linking group X ^b1 may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.
As an aliphatic hydrocarbon group, the aliphatic hydrocarbon group etc. which contain a ring in a linear or branched aliphatic hydrocarbon group or a structure are mentioned.
The hetero atom in the divalent linking group containing a hetero atom is an atom other than a carbon atom and a hydrogen atom, and examples thereof include an oxygen atom, a nitrogen atom, a sulfur atom, and a halogen atom.
When X ^b1 is a divalent linking group containing a hetero atom, —X ^b1 OH is — (CH ₂ ) _m —O— (X ^b2 O) _n —H [wherein, X ^b2 has 2 to 10 carbon atoms] And m is a number of 2 to 10, and n is a number of 1 to 10].
X ^b2 is a divalent linking group having 2 to 10 carbon atoms. Examples of the divalent linking group include a divalent hydrocarbon group, a divalent linking group containing a hetero atom, and the like.
The hydrocarbon group as the divalent linking group X ^b2 may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
When X ^b2 is a divalent linking group containing a hetero atom, X ^b2 is —C (= O) —X ^b3 — [wherein, X ^b3 is a divalent hydrocarbon group having 1 to 10 carbon atoms] . ] Is preferable. The number of carbon atoms of X ^b3 is preferably 2 to 8, more preferably 3 to 6, 5 being most preferred. As a bivalent hydrocarbon group, an alkylene group is preferable, For example, ethylene group, a propylene group, a butylene group, pentylene group is mentioned.
m is a number of 2 to 10. m is preferably 2 to 8, more preferably 2.
n is a number of 1 to 10. 2-8 are preferable and, as for n, 3-5 are more preferable.
As the structural unit (a2), one type of structural unit may be used alone, or two or more types may be used in combination.

  12-30 mol% is preferable with respect to the total mole number of all the structural units which comprise an acrylic resin (A), and, as for the ratio of a structural unit (a2), 16-25 mol% is more preferable. By setting the ratio of the structural unit (a2) within the above numerical range, it is possible to impart good adhesion and chipping resistance.

<Other configuration unit>
The acrylic resin (A) contained in the resin composition of the present invention may contain other structural units other than the structural units (a1) and (a2).
As other structural units, (meth) acrylates such as methyl (meth) acrylate and butyl (meth) acrylate; carboxyl group-containing monomers such as (meth) acrylic acid; styrene, α-methylstyrene, vinyl toluene, paramethylstyrene Styrene derivatives such as chlorostyrene; vinyl esters such as vinyl acetate and vinyl propionate; halogenated vinyl monomers such as vinyl chloride and vinylidene chloride; acrylamide, diacetone acrylamide, N-methylol acrylamide, acrylonitrile, methacrylamide, methacryl amide Those derived from nitrogen-containing vinyl monomers such as nitrile are mentioned. The other constituent units may be used alone or in combination of two or more.

The hydroxyl value of the acrylic resin (A) is 30 to 50 mg KOH / g, and 35 to 45 mg KOH / g is more preferable. By setting the hydroxyl value to the lower limit value or more, weather resistance and chipping resistance can be easily improved. By setting the hydroxyl value to the upper limit value or less, adhesion such as initial adhesion and water resistance can be easily improved.
In addition, the hydroxyl value in this specification is the numerical value calculated | required according to JISK1557-1: 2007 "plastics-polyurethane raw material polyol test method-part 1: How to obtain a hydroxyl value."

The glass transition point of the acrylic resin (A) is -30 ° C or less, preferably -35 ° C or less, and more preferably -40 ° C or less.
By setting the glass transition point to the upper limit value or less, adhesion such as initial adhesion and water adhesion can be easily improved, and chipping resistance can be easily improved.
In addition, the glass transition point in this specification can be measured by a differential scanning calorimetry method (DSC method) based on JISK7121.

The acrylic resin (A) can be synthesized by a known polymerization method such as radical polymerization.
Examples of radical polymerization initiators used for the polymerization include cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 1,1-bis (t-butylperoxy) -3,3,5 -Trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, cumene hydroperoxide, 2,5-dimethylhexane-2, 5-Dihydroperoxide, 1,3-bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, diisopropylbenzene peroxide, t-Butylcumyl peroxide, decanoyl peroxide , Lauroyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-t-amyl peroxide, bis (t-butylcyclohexyl) peroxydicarbonate, t-butylperoxybenzoate, 2,5- Peroxide type polymerization initiators such as dimethyl-2,5-di (benzoylperoxy) hexane and t-butylperoxy-2-ethylhexanoate; 2,2'-azobis (isobutyronitrile), 1 1,1-azobis (cyclohexane-1-carbonitrile), azocumene, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 4,4 ′ -Azobis (4-cyanovaleric acid), 2- (t-butylazo) -2-cyanopropane, 2,2'-azobis (2,4,5 Examples include azo polymerization initiators such as 4-trimethylpentane), 2,2'-azobis (2-methylpropane), and dimethyl 2,2'-azobis (2-methylpropionate).

  The resin composition of the present invention may contain, in addition to the acrylic resin (A), an isocyanate, a polyol, a silane coupling agent, a solvent and the like.

  As the isocyanate, at least one type (B) selected from isocyanates in which the polyester component is introduced in the skeleton, isocyanates in which the polycarbonate component is introduced in the skeleton, and isocyanates in which the polyether component is introduced into the skeleton (B) is mentioned. An isocyanate (B) may be used individually by 1 type, and may use 2 or more types together.

  The isocyanate may be a hard type isocyanate other than the soft type isocyanate (B) (hereinafter referred to as isocyanate (C)). Examples include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), xylene diisocyanate (XDI) and oligomers or polymers thereof. An isocyanate (C) may be used individually by 1 type, and may use 2 or more types together.

  The content of isocyanate is preferably such that the ratio of molar equivalent of isocyanate group (-NCO) to molar equivalent 1 of hydroxyl group contained in the primer layer is 0.5 to 2.0, and 1.0 to 1.6. More preferable. The molar equivalent ratio of isocyanate groups is the ratio of the total molar equivalents of the soft type isocyanate (B) and isocyanate (C). Here, the molar equivalent of the hydroxyl group which a primer layer contains is a molar equivalent of the hydroxyl group which an acrylic resin (A) and a polyol (D) have. When the ratio of the molar equivalent of the isocyanate group to the molar equivalent 1 of the hydroxyl group is at least the lower limit value, chipping resistance and water resistance of the primer layer can be easily improved. It is easy to improve the adhesiveness with a metal plating layer as it is below an upper limit.

  The resin composition of the present invention may contain a polyol (D). The polyol (D) has a role of further improving the chipping resistance. The polyol (D) is preferably at least one selected from polyester polyols, polycarbonate polyols, and polycarbonate polyols modified with polyester. A polyol (D) may be used individually by 1 type, and may use 2 or more types together.

The weight average molecular weight (Mw) of the polyol (D) is preferably 500 to 50,000, more preferably 700 to 30,000, and still more preferably 800 to 10,000. It becomes easy to improve the chipping resistance of a primer layer as Mw of a polyol (D) is more than a lower limit. It becomes easy to mix with the said acrylic resin (A) as Mw of a polyol (D) is below an upper limit, and it can prevent that a primer layer becomes cloudy.
In the present specification, the weight average molecular weight can be measured by gel permeation chromatography (GPC) method (in terms of polystyrene).

  20-200 mgKOH / g is preferable, as for the hydroxyl value of a polyol (D), 40-180 mgKOH / g is more preferable, and 50-120 mgKOH / g is further more preferable. It becomes easy to improve the chipping resistance of a primer layer as the hydroxyl value of a polyol (D) is more than a lower limit. It becomes easy to improve the adhesiveness with a metal plating layer as the hydroxyl value of a polyol (D) is below an upper limit.

The mass ratio (hereinafter also referred to as A / D ratio) represented by the acrylic resin (A) / polyol (D) is not particularly limited as long as the effects of the present invention are exhibited, but it is 60/40 to 100/0. Is preferred.
0-66 mass parts is preferable with respect to 100 mass parts of acrylic resins (A), and, as for content of a polyol (D), 0-40 mass parts is more preferable.

  The resin composition of the present invention may contain a silane coupling agent (E). By including the silane coupling agent (E), good adhesion can be exhibited even on a substrate whose adhesion has been deteriorated by being left under a high temperature and high humidity environment.

  The silane coupling agent (E) preferably contains glycidyl trimethoxysilane. The silane coupling agent (E) includes, as glycidyl trimethoxysilanes, glycidyloxymethyltrimethoxysilane, glycidyloxyethyltrimethoxysilane, glycidyloxypropyltrimethoxysilane, glycidyloxycyclohexyltritrimethoxysilane, and It is preferable to contain at least one selected from sidyloxyphenyltrimethoxysilane. More preferably, as glycidyl trimethoxysilanes, glycidyloxymethyltrimethoxysilane, glycidyloxyethyltrimethoxysilane, glycidyloxypropyltrimethoxysilane, glycidyloxycyclohexyltritrimethoxysilane, glycidyloxyphenyltrimethoxy It contains two or more selected from silanes. A silane coupling agent (E) may be used individually by 1 type, and may use 2 or more types together.

  The amount of the silane coupling agent (E) is preferably 1 to 10 parts by mass, and more preferably 2 to 7 parts by mass with respect to 100 parts by mass of the acrylic resin (A). Moreover, when a resin composition contains a polyol (D), content of a silane coupling agent (E) is 1 with respect to the total mass 100 mass parts of an acrylic resin (A) and a polyol (D). -10 mass parts are preferable, and 2-7 mass parts are more preferable. By being left under the high temperature and high humidity environment as the lower limit value or more, good adhesion can be exhibited even on the metal plating surface whose adhesion is deteriorated. It is easy to improve the weather resistance of a coating film as it is below an upper limit, and the fall of a pot life can be suppressed.

The resin composition of the present invention may contain a solvent (F).
As the solvent (F), ester solvents such as ethyl acetate, propyl acetate, butyl acetate, methoxybutyl acetate, amyl acetate, methyl cellosolve acetate, cellosolve acetate, diethylene glycol monomethyl ether acetate, carbitol acetate; dioxane, ethylene glycol diethyl ether And ether solvents such as ethylene glycol dibutyl ether; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone. These solvents (F) may be used alone or in combination of two or more.

  Furthermore, a dye for adjusting the light transmittance and the color tone, a plasticizer, a reinforcing agent, a photosensitizer, a light stabilizer, a chain transfer agent, and an ultraviolet ray absorption as needed within the range not impairing the effects of the present invention. Additives such as agents, antioxidants, viscosity modifiers, tackifiers, foam stabilizers, antifoam agents, mildew proofing agents, preservatives and the like can be blended. These additives may be used alone or in combination of two or more, as long as the effects of the present invention are not impaired.

«Method for producing resin composition»
The resin composition of the present invention can be prepared by mixing the respective components by a known method.

«Painting structure»
As shown in FIG. 1, the coated structure 10 of the present invention comprises a metal plating layer 1, a primer layer 2 located on the metal plating layer 1 and formed of the resin composition, and the primer layer 2. And a top coat layer 3 located on the upper side.

<Metal plating layer>
The metal plating layer 1 is formed on a base material. The substrate is made of, for example, plastic, fiber reinforced plastic or metal. Plastics are, for example, polyacetal (POM), polyamide (PA), polycarbonate (PC), polyphenylene ether (PPE), polybutylene terephthalate (PBT), acrylonitrile butadiene styrene copolymer (ABS), polymethyl methacrylate (PMMA) , Polypropylene (PP). Fiber reinforced plastics are, for example, carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP). The metal is, for example, steel or aluminum. Among them, ABS resin is preferable.
The thickness of the substrate is, for example, 2 to 10 mm. In the present specification, the thickness is measured by a thickness gauge.
The metal plating layer 1 is, for example, chromium plating, zinc plating, cadmium plating, tin plating, nickel plating, gold plating, silver plating, copper plating, platinum plating or alloy plating of these. Among them, chromium plating is preferable. The thickness of the metal plating layer is, for example, 2 to 100 μm.

<Primer layer>
The primer layer 2 is formed of the resin composition.
The thickness of the primer layer 2 is preferably 3 to 30 μm, more preferably 5 to 20 μm, and still more preferably 7 to 15 μm. When the thickness of the primer layer 2 is equal to or more than the lower limit value, adhesion becomes easy to improve, and chipping resistance becomes easy to improve. It becomes easy to suppress a hardness fall as the thickness of primer layer 2 is below an upper limit.

<Top coat layer>
The top coat layer 3 is formed of a resin composition for top coat containing a polyol (G) and an isocyanate (H).

The polyol (G) contains an acrylic polyol.
The acrylic polyol can be synthesized, for example, by copolymerizing an acrylic monomer and a hydroxyl group-containing (meth) acrylic monomer.
As a hydroxyl-containing (meth) acrylic monomer, a hydroxyalkyl (meth) acrylate etc. are mentioned, for example. As said hydroxyalkyl (meth) acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, 1, 4- cyclohexanediol monoacrylate etc. are mentioned, for example.
The alkyl group of the hydroxyalkyl (meth) acrylate may be linear, branched or cyclic, preferably has 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms.
These hydroxyl group-containing (meth) acrylic monomers may be used alone or in combination of two or more.

Examples of the acrylic monomer include (meth) acrylic acid and (meth) acrylic acid alkyl ester. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acrylic acid- n-butyl, isobutyl (meth) acrylate and the like can be mentioned.
These acrylic monomers may be used alone or in combination of two or more.
Polyol (G) may contain polycarbonate diol in addition to acrylic polyol.
A polyol (G) may be used individually by 1 type, and may use 2 or more types together.

  1,000-100,000 are preferable, as for the weight average molecular weight (Mw) of a polyol (G), 5,000-50,000 are more preferable, and 7,000-40,000 are more preferable. When the Mw of the polyol (G) is at least the lower limit value, it is easy to prevent the occurrence of appearance defects such as repelling defects. It becomes easy to prevent that leveling property falls that Mw of a polyol (G) is below an upper limit.

  The hydroxyl value of the polyol (G) is preferably 10 to 150 mg KOH / g, more preferably 20 to 100 mg KOH / g, and still more preferably 25 to 80 mg KOH / g. When the hydroxyl value of the polyol (G) is at least the lower limit value, it is easy to improve the chipping resistance of the top coat layer. When the hydroxyl value of the polyol (G) is less than or equal to the upper limit value, the drying property can be easily improved.

  The content of the isocyanate (H) is preferably such that the ratio of the molar equivalent of isocyanate group (-NCO) to the molar equivalent 1 of the hydroxyl group contained in the topcoat layer is 0.8 to 2.0. More preferably, it is 1.1-1.6. Here, the molar equivalent of the hydroxyl group which a topcoat layer contains is a total molar equivalent of the hydroxyl group which a polyol (G) has. When the ratio of the molar equivalent of the isocyanate group to the molar equivalent 1 of the hydroxyl group is at least the lower limit value, the scratch resistance and chemical resistance of the top coat layer can be easily improved. Below the upper limit value, it is possible to prevent the curing shrinkage from becoming large and to improve the adhesion.

  10-50 micrometers is preferable and, as for the thickness of the topcoat layer 3, 15-30 micrometers is more preferable. When the thickness of the top coat layer 3 is not less than the lower limit value, the chipping resistance can be easily improved. If the thickness of the top coat layer is less than or equal to the upper limit value, curing shrinkage is prevented from becoming large, and adhesion to the metal plating layer is easily improved.

  The total thickness of the primer layer 2 and the top coat layer 3 is preferably 15 to 80 μm, more preferably 20 to 50 μm, and still more preferably 25 to 40 μm. If the total thickness is equal to or more than the lower limit value, it is easy to prevent various performances from being reduced. Adhesiveness is easy to be improved as total thickness is below an upper limit.

  Furthermore, a dye for adjusting the light transmittance and the color tone, a plasticizer, a reinforcing agent, a photosensitizer, a light stabilizer, a chain transfer agent, and an ultraviolet ray absorption as needed within the range not impairing the effects of the present invention. Additives such as agents, antioxidants, viscosity modifiers, tackifiers, foam stabilizers, antifoam agents, mildew proofing agents, preservatives and the like can be blended. These additives may be used alone or in combination of two or more, as long as the effects of the present invention are not impaired.

«Method of manufacturing coated structure»
The method for forming the metal plating layer 1 on the surface of the substrate is not particularly limited, and examples thereof include hot-dip plating and electroplating.
The primer layer 2 can apply | coat the resin composition of this invention to the surface of a metal plating layer, and can dry and form it.
The topcoat layer 3 can be formed by applying the resin composition for topcoat to the surface of the primer layer and drying it.
A color pigment may be further blended in one or both of the resin composition and the resin composition for top coat for the purpose of giving a characteristic design.
After the resin composition of the present invention is applied, the resin composition for top coat is applied and dried, whereby the primer layer 2 and the top coat layer 3 can be simultaneously formed.

  The coating method of the resin composition and the resin composition for top coats is not particularly limited, and the coating can be performed by a known method. Known coating methods are, for example, brush coating, roller coating, spraying with a spray gun, roll coater, and immersion. A coating of a desired thickness may be formed by one coating, or a coating of a desired thickness may be formed by multiple coating.

  The method for drying the resin composition and the resin composition for top coat after coating is not particularly limited, and may be natural drying or forced drying. Specifically, it may be dried for about 30 to 90 minutes in an atmosphere of 60 to 80 ° C.

EXAMPLES The present invention will be described in more detail using the following examples, but the present invention is not limited to these examples.
The amounts (parts by mass) of each monomer and each reagent are shown in Tables 1 and 2. The numerical value in the parenthesis represents the ratio (mol%) of each constitutional unit to the total number of moles of all constitutional units constituting the obtained acrylic resin (A). In addition, the ratio of each structural unit is calculated from the preparation amount.
The raw materials of the used coating film are as follows.

«Materials used»
MMA: methyl methacrylate, acrylic ester M, manufactured by Mitsubishi Rayon.
SMA: Stearyl methacrylate, Acryester S, manufactured by Mitsubishi Rayon.
-LMA: lauryl methacrylate, acrylic ester L, manufactured by Mitsubishi Rayon.
N-BMA: n-butyl methacrylate, acrylate B, manufactured by Mitsubishi Rayon.
-BA: butyl acrylate, manufactured by Toagosei.
· FM5: Plaxel FM5, unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone, in formula (a2), R ^b1 = methyl group, -X ^b1 OH =-(CH ₂ ) ₂ O [C (= O) (CH ₂ ) ) ₅ O] H, manufactured by Daicel Corporation.
-FM3: Plaxel FM3, unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone, in formula (a2), R ^b1 = methyl group, -X ^b1 OH =-(CH ₂ ) ₂ O [C (= O) (CH ₂ ) ) ₅ O] H, manufactured by Daicel Corporation.
HEA: 2-hydroxyethyl acrylate, light ester HOA (N), manufactured by Kyoeisha Chemical Co., Ltd.
HH: methacryloyloxyethyl hexahydrophthalic acid, light ester HO-HH (N), manufactured by Kyoeisha Chemical.
I-BAC: isobutyl acetate, manufactured by Wako Pure Chemical Industries.
ABN-E: azobisisobutyronitrile, reaction initiator, manufactured by Wako Pure Chemical Industries.
EAC: ethyl acetate, manufactured by Wako Pure Chemical Industries.
Acrylic polyol: manufactured by Taisei Fine Chemical Co., Ltd., acrylic polyol # 6000 series, product number: 6BF-203, Mw: 26,000, hydroxyl value: 30 mg KOH / g).
-Tinuvin 384-2: trade name, UV absorber, manufactured by BASF Japan Ltd.
-Tinuvin 292: trade name, UV absorber, manufactured by BASF Japan Ltd.
Isocyanate: A polymer of HDI, trade name "Sumidur N-3200", manufactured by Sumitomo Bayer Urethane Co., Ltd.
-Polycarbonate diol: Hydroxyl value: 140 mg KOH / g, trade name "Duranol T5650J", manufactured by Asahi Kasei Chemicals.

(Examples 1-8, comparative examples 1-8)
200 g of isobutyl acetate was charged into a four-necked flask of 1 L vessel equipped with a stirrer, a cooler, a nitrogen sealing machine, a thermometer, and a monomer dropping device, and was heated until the internal temperature became 90.degree. Then, a mixed solution of monomers, solvents, and a reaction initiator shown in the table is added dropwise thereto over 1 hour, and an additional reaction initiator is added 1 hour after the end of the dropwise addition, and the reaction is then maintained at 90 ° C. for 4 hours It finished and obtained acrylic resin (A).
The glass transition point and the hydroxyl value of the obtained acrylic resin (A) were determined by the following method.
What mixed the obtained acrylic resin (A) and ethyl acetate by mass ratio of 80/20 was made into the resin composition (for primer layer formation).
Separately from this, acrylic polyols (glass transition temperature: 24 ° C., hydroxyl value: 30 mg KOH / g, Mw: 26,000, nonvolatile content: 50%), ethyl acetate, tinuvin 384-2 (trade name), tinuvin 292 ( What mixed the brand name) and the mass ratio of 80 / 18.5 / 1.0 / 0.5 was made into the resin composition for top coats.
What prepared trivalent chromium plating on the ABS base material was prepared. After plating treatment, left at room temperature, 60% RH for 1 hour (plating material X), after plating treatment, left at room temperature, 60% RH for 2 weeks (plating material Y), after plating treatment, 50 ° C. , And those left for two weeks at 95% RH (plating material Z) were prepared respectively.
An isocyanate was added to the resin composition (for primer layer formation) and the resin composition for top coats so that NCO / OH (molar ratio) = 1.1, respectively, and diluted with an optional organic solvent. The resin composition and the resin composition for top coat are applied in the order of 20 μm by spray coating on the above-mentioned plated materials X to Z in a thickness of 20 μm, and forcibly dried at 80 ° C. for 60 minutes. , A coated article comprising a painted structure comprising a top coat layer was formed. The following tests were performed using the obtained coated article. The results of the test are shown in Tables 1 and 2. In the evaluation results of the table, the left shows using plating material X, the center shows using plating material Y, and the right shows using plating material Z. In the table, "-" means that the evaluation is not performed.

(Example 9)
A mixture of the obtained acrylic resin (A) and polycarbonate diol in a mass ratio of 90:10 and a mixture of ethyl acetate in a mass ratio of 80/20 and a resin composition (for forming a primer layer) A painted product was formed in the same manner as above except for the above.

<Glass transition point>
The glass transition point was determined by differential scanning calorimetry (DSC method) based on JIS K7121.

<Hydroxyl number>
The hydroxyl value was determined in accordance with JIS K 1557-1: 2007 “Plastics—Polyurethane raw material polyol test method—Part 1: Determination of hydroxyl value”.

<Adhesiveness>
The adhesion of the coated film after the coated product was left at room temperature for 96 hours was evaluated based on the following evaluation criteria.
○: Peeling of the coating film is not confirmed.
X: Peeling of the coating film is confirmed.

<Weatherability and chipping resistance>
The coated product was left to stand at room temperature for 96 hours, and then irradiated with 500 MJ / cm ² of ultraviolet light using an XENON tester to evaluate the appearance and chipping resistance of the coated structure. The chipping resistance was evaluated in the same manner as <chipping resistance> described later except that the chipping resistance was measured after irradiation with ultraviolet light.
○: There is no abnormality in the appearance, and the chipping resistance does not decrease after irradiation with ultraviolet light.
Fair: There is no abnormality in the appearance, but the chipping resistance is reduced after irradiation with ultraviolet light.
X: The appearance is abnormal, and the chipping resistance is reduced after the ultraviolet irradiation.

<Water resistance>
The coated article was left to stand at room temperature for 96 hours, and then immersed in warm water at 40 ° C. and 60 ° C. for 300 hours to evaluate the adhesion and appearance of the coated structure.
○: The coating did not peel off at either 40 ° C. or 60 ° C.
B: The coating film is not peeled off at either 40 ° C. or 60 ° C., but appearance abnormalities such as blisters and discoloration are observed.
X: Peeling of the coating film is observed at either 40 ° C. or 60 ° C.

<Chipping resistance>
After leaving the coated product to stand at room temperature for 96 hours, 100 g of crushed stone No. 7 was made to collide at a collision angle of 90 ° at a pressure of 4 kg / cm ² using a flying stone tester at -20 ° C, and the number of scratches reaching the metal plating layer surface The chipping resistance was evaluated based on the following evaluation criteria.
A: The number of scratches reaching the surface of the metal plating layer is 10 or less (practical level).
B: The number of scratches reaching the surface of the metal plating layer is in the range of 11 to 50 (lower limit of practical use).
C: The number of scratches reaching the surface of the metal plating layer is 51 or more (not suitable for practical use).

<Appearance>
After the coated product was left to stand at room temperature for 96 hours, the appearance of the coated structure was visually evaluated.
○: A coating film having a sense of transparency is formed, and the metallic gloss of the metal plating layer is not inhibited.
X: The haze is confirmed in the coating film, and the metallic gloss of the metal plating layer is inhibited.

In Examples 1 to 9 to which the present invention was applied, a coated structure excellent in adhesion, weather resistance, water resistance, chipping resistance and appearance was obtained.
On the other hand, in Comparative Examples 1 and 2 having a glass transition temperature of -30 ° C. or higher, adhesion, weather resistance, water resistance and chipping resistance were inferior.
In Comparative Examples 3 and 4 having a hydroxyl value of less than 30 mg KOH / g, adhesion, weather resistance, water resistance and chipping resistance were inferior.
Comparative Example 5 using HEA instead of the structural unit (a2) was inferior in adhesion, weather resistance, water resistance and chipping resistance.
In Comparative Example 6 having a hydroxyl value of more than 50 mg KOH / g, adhesion and water resistance were poor.
Comparative Examples 7 and 8 in which the proportion of the structural unit (a1) was less than 16 mol% were inferior in adhesion and water resistance.
From the above, it was found that according to the resin composition to which the present invention is applied, the resulting coated structure is excellent in adhesion, weather resistance, water resistance, chipping resistance and appearance.

1 metal plating layer 2 primer layer 3 top coat layer 10 painted structure

Claims (5)

The structural unit (a1) represented by the following formula (a1),
An acrylic resin (A) having a structural unit (a2) represented by the following formula (a2),
The hydroxyl value of the acrylic resin (A) is 30 to 50 mg KOH / g,
The glass transition point of the acrylic resin (A) is -30 ° C. or less,
The proportion of the structural unit (a1) is, relative to the total number of moles of all the structural units that constitute the acrylic resin (A), the Ri der 16 mol% or more,
The proportion of the structural unit (a2) is, relative to the total number of moles of all the structural units that constitute the acrylic resin (A), the Ru der least 12 mol%, the resin composition.

[In the formula (a1), R ^a1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ^a2 is a monovalent hydrocarbon group having 10 to 20 carbon atoms, and in the formula (a2), R ^b1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, -X ^b1 OH is-(CH ₂ ) _m -O- (X ^b2 O) _n -H, m is a number of 2 to 10 And n is a number of 1 to 10, X ^b2 is -C (= O)-X ^b3- , and X ^b3 is a divalent hydrocarbon group having 1 to 10 carbon atoms. ] The resin composition of Claim 1 whose ratio of the said structural unit (a2) is 30 mol% or less with respect to the total mole number of all the structural units which comprise the said acrylic resin (A). Furthermore, it contains a polyol (D),
The weight average molecular weight of the polyol (D) is 500 to 50000,
The resin composition of Claim 1 or 2 whose hydroxyl value of the said polyol (D) is 20-200 mgKOH / g.   A metal plating layer, a primer layer located on the metal plating layer and formed from the resin composition according to any one of claims 1 to 3, and a top coat layer located on the primer layer And painted structures. The top coat layer contains a polyol (G),
The coating structure according to claim 4, wherein the polyol (G) has a weight average molecular weight of 7,000 to 40,000 and a hydroxyl value of 25 to 80 mg KOH / g.

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