JP2627722B2 - Bake-curable coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a baking-curable coating composition which does not contain an organic solvent, has a fast curing reaction and provides a hard coating film having excellent scratch resistance. In particular, it is a coating composition suitable for pre-coated metal (PCM) requiring metal adhesion. Furthermore, the bake-curable paint of the present invention,
Depending on the combination of the components, either a two-pack coating or, in the case of using a blocked polyisocyanate, a one-pack coating can be used.

[0002]

2. Description of the Related Art Conventionally, as a coating material having a high curing speed and a hard coating film, a one-pack type baking coating material such as an acrylic melamine-based coating material, an acrylic urethane-based coating compounded with a blocked isocyanate cross-linking agent, and an acrylic resin have been known. There is a two-pack baking coating in which an isocyanate is blended with a resin immediately before use.

[0003]

However, since these paints have a high resin viscosity and contain an organic solvent, there are many problems in workability such as danger of inhaling steam and fire. In particular, recently, VOC regulations are becoming stricter overseas, and fire regulations are becoming stricter in Japan, and solvent-free bake-curable paints are desired.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a baking-curable coating composition which does not contain an organic solvent, has a high curing rate, and provides a hard coating film having excellent scratch resistance. By using a urethanization reaction and a radical polymerization reaction in combination, the coating composition of the present invention was reached.

That is, the present invention provides a (meth) acrylic monomer (A) having a tertiary amino group and a hydroxyl group, a polyisocyanate compound (B), a polyol (C), a radical polymerization initiator (D), and, if necessary, a pigment. A bake-curable coating composition characterized by comprising:

In the present invention, examples of the (meth) acrylic monomer (A) having a tertiary amino and a hydroxyl group include, for example, an addition reaction product of a compound having a primary or secondary amino group with glycidyl (meth) acrylate. A glycidylamine compound obtained by reacting a compound having a primary or secondary amino group with epichlorohydrin;
Further, (meth) acrylic acid is subjected to an addition reaction, 1
One or more primary amino groups, or two or more
Part (meth) acrylate obtained by adding an alkylene oxide (2 to 4 carbon atoms) to a compound having a primary amino group (addition mole number: usually 1 to 20), one or more primary amino groups in one molecule Or an amino group-containing glycidyl ether compound obtained by reacting an alkylene oxide (C2-4) adduct of a compound having two or more secondary amino groups (number of moles added: usually 1 to 20) with epichlorohydrin. And those obtained by the addition reaction of (meth) acrylic acid. Preferred among these are the addition reactants.

Specific examples of the compounds having a primary or secondary amino group in the above (1) include (1) aromatic amine compounds [aniline, o-, m- or p-toluidine, o-, m- or p- Phenylenediamine, 2, 4
-Or 2,6-tolylenediamine, diaminodiphenylmethane, N-alkyl (alkyl having 1 to 8 carbon atoms) aniline, p-aminopyridine, formalin condensate thereof and the like]; (2) aliphatic amine compound [methylamine ,
Alkylamines (C1-8) such as ethylamine, isopropylamine, n-butylamine, isobutylamine, and cyclohexylamine; dimethylamine, diethylamine, diisopropylamine, di-n-butylamine, diisobutylamine, dialkylamine such as dicyclohexylamine (carbon (Formulas 2 to 16), (poly) alkylene polyamines (having 1 to 8 carbon atoms) such as ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, iminobispropylamine, etc., monoethanolamine, monopropanolamine, diethanolamine, dipropanolamine, etc. And (3) aralkylamines such as benzylamine and xylylenediamine; Mixture of the above, and the like.
Preferred among those exemplified in (1) to (3) are aniline, o-, m- or p-toluidine and monoalkylamine having 1 to 8 carbon atoms.

The tertiary amino group present in (A) of the present invention becomes free by dissociation of the active hydrogen group in each component constituting the coating composition with the polyisocyanate compound (B) or the blocking agent. Polyisocyanate compound (a)
Promotes a urethanation reaction with an isocyanate group.

In the present invention, in addition to (A), 3
A (meth) acrylic monomer (A2) having a secondary amino group and no hydroxyl group and / or a (meth) acrylic monomer (A3) having a hydroxyl group and no amino group may be used in combination.

The (meth) acrylic monomer (A2) is obtained by adding an alkylene oxide (2-4 carbon atoms) to a compound having a primary or secondary amino group (addition mole number: usually 1-20). (Meth) acrylate in which the product is completely esterified. This first grade or 2
Examples of the compound having a secondary amino group include (1) to (3) exemplified in (A).

The (meth) acrylic monomer (A)
Examples of 3) include those obtained by reacting (meth) acrylic acid with a partial (meth) acrylate of a polyhydric alcohol or a glycidyl ether of a polyhydric alcohol. The polyhydric alcohols used in the above include the following (a) to (c). (A): alkylene glycol [ethylene glycol,
Propylene glycol, 1,4-butanediol, 1,
3-butylene glycol, neopentyl glycol,
1,6-hexanediol, etc.], cyclohexanediol, cyclohexanedimethanol, bisphenol A, bisphenol S, and dihydric alcohols such as naphthalene diol. (B): trivalent or higher alcohols such as glycerin, trimethylolpropane, trimethylolethane, hexanetriol, pentaerythritol, diglycerin, α-methylglucoside, sorbitol, xylitol, mannitol, glucose, fructose, and sucrose. (C): an adduct of (a) or (b) with an alkylene oxide (2-4 carbon atoms).

Examples of the polyisocyanate compound (B) in the present invention include aromatic polyisocyanates [diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), polyphenylpolymethylene polyisocyanate (crude MDI), naphthalene diisocyanate (NDI) and the like. ]; Aliphatic polyisocyanates [1,6-hexamethylene diisocyanate (HD
I), lysine diisocyanate (LDI), etc.]; alicyclic polyisocyanate [isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, etc.]; araliphatic polyisocyanate [xylylene diisocyanate ( XDI), tetramethylxylene diisocyanate (TMXDI) and the like]; modified products thereof (such as buret group, isocyanurate group, carbodiimide group, oxazolidine group-containing modified product and trimethylolpropane adduct); and these polyisocyanates and their molecular weights Urethane prepolymers having terminal isocyanate groups consisting of 50 to 5,000 active hydrogen-containing compounds are exemplified. Further, in the present invention, as the polyisocyanate compound (B), a blocked product (B1) of the above-mentioned polyisocyanate compound can also be used. In that case, it acts as a free polyisocyanate dissociated from the blocking agent by heating during baking, and can be used as a one-pack bake-curable coating. Further, the urethane prepolymer having a terminal isocyanate group can be obtained by reacting a polyol or a polyamine having two or more active hydrogens such as a hydroxyl group and an amino group with the above-mentioned polyisocyanate. As this polyol, those mentioned below for the polyol (C) can be used. Aromatic polyisocyanates, modified products thereof, and urethane prepolymers are preferable because they have excellent coating properties as polyurethane and high reactivity as compared with other aliphatic and alicyclic polyisocyanates.
On the other hand, aliphatic and alicyclic polyisocyanates and their modified products, and urethane prepolymers are excellent in light resistance, and thus are particularly suitable for paints for coating members used outdoors. Although the reactivity is lower than that of the aromatic polyisocyanate, a urethanization catalyst for an organometallic compound (such as dibutyltin dilaurate and lead octenoate) and an amine (such as triethylamine and triethylenediamine) may be used in combination. When used as one component of a two-pack coating, it is preferable that the viscosity be low in terms of workability. When a modified product or a prepolymer having three or more isocyanate groups in the molecule is used, the coating film hardness increases.

As the blocking agent for use as the blocked product (B1) in the present invention, oxime compounds (eg, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, cyclohexanone oxime), lactams (eg, ε-caprolactam, γ-butyrolactam) Phenols (phenol, m-cresol, etc.), dialkylphenols (xylenol, di-t-butylphenol, etc.), active methylene compounds (diethyl malonate, acetylacetone, ethyl acetoacetate, etc.), alcohols (methanol, ethanol, etc.), mercaptans (Butyl mercaptan, etc.) and the like, and these can be used in combination. Of these, preferred
Oxime compounds and lactams. In the blocking reaction, the blocking agent is usually added to the isocyanate group in an amount of 0.1 to 0.1%.
3 to 2, preferably 1.05 to 1.5 equivalents are added, and the reaction is usually performed at 50 to 150 ° C. At this time, the above-mentioned urethanization catalyst can be added to accelerate the reaction.

The polyol (C) in the present invention includes low-molecular-weight polyhydric alcohols and high-molecular-weight polyols. As the low molecular weight polyhydric alcohol, the aforementioned (A)
Examples include the polyhydric alcohols (a) to (c) exemplified in the section 3) and mono-, di- or tri-alkanolamines. Various polyester polyols, polyether polyols, and other polymer polyols can be used as the polymer polyol. As the polyester polyol, for example, an acid component such as an aliphatic dicarboxylic acid such as adipic acid and sebacic acid and an aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid; and carbon atoms of 2 to 2 such as ethylene glycol, propylene glycol, and neopentyl glycol. Polycaprolactone polyols; polyester polyols having aliphatic diols, ether glycols such as diethylene glycol and dipropylene glycol, and spiro glycols as diol components. For example, adipate-based polyols such as polyethylene adipate polyol, polyethylene propylene adipate polyol, and polybutylene adipate polyol; terephthalic acid-based polyols (for example, Toyobo Co., Ltd., trade name Byron); Can be Also, as a polyether polyol,
Examples include polyoxyethylene polyol, polyoxypropylene polyol, polyoxytetramethylene polyol, and random and block copolymers thereof. Further, examples of other polymer polyols include, for example, polycarbonate polyols and polybutadiene polyols. These polyols may be used in combination of two or more low molecular weight polyhydric alcohols and high molecular weight polyols. The number of hydroxyl groups in the molecule of the polyol (C) used in the present invention is 2 or more, and in particular, when a compound having 3 or more is used in combination, the coating film hardness increases. Although the molecular weight is not particularly limited, the use of a low-molecular-weight polyol increases the hardness of the coating film. Conversely, the use of a high-molecular-weight polyol provides flexibility.

The radical polymerization initiator (D) of the present invention is not particularly limited, and peroxides which generate radicals by heat, such as peroxides and azo compounds, can be used. Examples of peroxides include diacyl peroxides [dibenzoyl peroxide, lauroyl peroxide, etc.]; dialkyl peroxides [di-tert-butyl peroxide, dicumyl peroxide, etc.]; peroxyesters [tert-butyl] Peroxybenzoate, tert-
Butylperoxy-2-ethylhexanoate and the like];
Ketone peroxides [methyl ethyl ketone peroxide, cyclohexanone peroxide, etc.]; peroxydicarbonates [bis (4-tert-butylcyclohexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, etc.]; peroxyketals [1, 1-bis (tert-butylperoxy) 3,
3,5-trimethylcyclohexane, 2,2-bis (te
rt-butylperoxy) octane and the like. As the azo compound, for example, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis-
(2,4-dimethylvaleronitrile) (AVN) and the like. These may be used in combination of two or more.

Further, a feature of the present invention is that a tertiary amino group in (A) of the present invention promotes decomposition of the polymerization initiator (D), so that a rapid curing reaction proceeds.

The coating composition of the present invention may contain a reaction accelerator (E) to increase the reaction rate of the radical polymerization reaction. Examples of the accelerator include metal salts of organic acids (such as cobalt naphthenate, magnesium naphthenate, and cobalt acetoacetate), tertiary amines (such as dimethylaniline), and quaternary ammonium salts. further,
A co-catalyst, such as β-diketone (acetylacetone, dibenzoylmethane, etc.), which enhances the effects of the radical polymerization initiator and the reaction accelerator, can also be used.

The viscosity of the coating composition of the present invention can be adjusted by using another vinyl monomer (F) in combination.

Other vinyl monomers (F) include (meth) acrylates obtained by completely esterifying the above-mentioned polyhydric alcohols (a) to (c); (meth) acrylates of aliphatic monohydric alcohols; styrene; aromatic vinyl compounds such as α-methylstyrene, o-, m- or p-methylstyrene, and divinylbenzene; vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate; itaconic acid and its esters, (meth) Acrylonitrile and the like.

In the coating composition of the present invention, the amount of the polyisocyanate compound (B) used [blocked product (B1)
Free dissociated polyisocyanate if used)
Is a hydroxyl group-containing compound in the coating composition (A),
(A3), the molar ratio of the isocyanate group of (B) to the hydroxyl group of (C) (NCO group / OH group) is usually 0.7 to 0.7.
1.2, preferably in the range of 0.9 to 1.1.

The amount of the polyol (C) used differs between the low-molecular-weight polyhydric alcohol and the high-molecular-weight polyol.
It is usually 10 to 200 parts by weight, preferably 20 to 100 parts by weight, based on 00 parts by weight.

The amount of the radical polymerization initiator (D) used is
Usually 0.1 parts by weight based on a total of 100 parts by weight of (A) to (C).
10 to 10 parts by weight, preferably 0.2 to 5 parts by weight.

The amount of the reaction accelerator (E) used depends on the type of the catalyst used, but the total amount of (A) to (C) is 100%.
It is usually 0 to 5 parts by weight based on parts by weight.

The amount of the other vinyl monomer (F) to be used depends on the viscosity and the coatability of the liquid mixture, but (A) to (C)
Is usually 0 to 300 parts by weight with respect to 100 parts by weight in total.

The coating composition of the present invention may be applied as a two-part coating which is divided into two stable components during storage, or may be applied to a one-part coating by using a blocked polyisocyanate. May be.

As the former two-pack type paint, the components (A) to (D) that react with each other are divided into a mixture of the first and second liquids, and the mixture is applied to an actual adherend. Before use, the two solutions are mixed and used. As a method of dividing the mixture into two components, for example, the first component is a mixture of a (meth) acrylic monomer (A), a polyol (C) and, if necessary, a reaction accelerator (E), and the second component is a polyisocyanate. A method of preparing a mixture of the compound (B) and the radical polymerization initiator (D) may be mentioned, but the method is not limited. The pigment may be blended in either the first liquid or the second liquid, but is usually blended in the same liquid as the polyol. (A), (A3) and (C) having a hydroxyl group and (B) having an isocyanate group should not be combined in advance as the same compounding liquid. The radical polymerization initiator (D) is a vinyl monomer (meth) acrylic monomer (A), (A2),
It is preferable not to combine (A3) and the reaction accelerator (E) in advance as the same blended liquid.

[0027] The latter one-pack type paint can be used from the beginning (A) by using a blocked polyisocyanate.
All of (B1), (C) and (D) may be blended.

As the pigment, inorganic pigments (titanium oxide, iron oxide, graphite, cadmium oxide,
And organic pigments (eg, azo, azo lake, phthalocyanine, quinacridone, and isoindolinone organic pigments). The pigment is usually 0 to 200 with respect to the total amount of the coating composition.
% By weight.

In addition to the above, the coating composition of the present invention usually comprises
Various known paint resins, additives, and solvents to be added to the paint can be blended. Acrylic as paint resin,
Examples include urethane, melamine, silicone, ester, and epoxy paint resins. Examples of the various additives include a surfactant, a pigment dispersant, a plasticizer, a thixotropy-imparting agent, a leveling agent, a matting agent, an ultraviolet absorber, and an antioxidant.

The coating composition of the present invention can be obtained by appropriately selecting (A) to (D) and the above-mentioned additives according to the purpose and mixing them. As a mixing apparatus for such mixing, a ball mill, a kneader, a sand grinder, a roll mill, a flat stone mill and the like can be mentioned.

The coating method of the coating composition of the present invention is optional, and includes, for example, coating (eg, blade coater, air knife coater, roll coater, curtain coater, bar coater, gravure coater), spray coating, dip coating, It can be applied by brush coating or the like. After being applied to the substrate, it is baked and cured usually at 90 ° C. or higher, preferably 100 to 170 ° C. in a drier or the like.

[0032]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Parts and% are parts by weight and% by weight, respectively.
Represents The abbreviations of the main raw materials used are as follows. Raw material used NP: Light ester NP (manufactured by Kyoeisha Yushi, neopentyl dimethacrylate) PBZ: Perbutyl Z (manufactured by Nippon Yushi: t-butyl peroxybenzoate)

Production Example 1 Glycidyl methacrylate 284 was placed in a glass reactor equipped with a dropping funnel, a thermometer, a reflux condenser, and a stirring rod.
Of n-butylamine 73 at 30 ° C. or lower while stirring.
Part from the dropping funnel over 2 hours.
After aging at 0 ° C. for 3 hours and at 80 ° C. for 3 hours, a transparent liquid reaction product was obtained. In 30 parts of this, 1,4-butanediol 1
To a mixture of 0 part and 20 parts of NP, 20 parts of titanium oxide was added and kneaded with a ball mill to prepare a first liquid X1.

Production Example 2 In the same reactor as in Production Example 1, 284 parts of glycidyl methacrylate were charged, and the temperature was raised to 90 ° C. with stirring. To this, 93 parts of aniline was added dropwise from a dropping funnel over 2 hours, and after completion of the addition, the mixture was aged at 120 ° C. for 6 hours to obtain a yellow transparent liquid reaction product. To 30 parts of the mixture, 20 parts of titanium oxide was added to a mixture of 10 parts of 1,4-butanediol and 20 parts of NP, and the mixture was kneaded with a ball mill to prepare a first liquid X2.

Production Example 3 In a glass reactor equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 250 parts of a polyester diol having a molecular weight of 500 obtained from adipic acid and 1,4-butanediol and isophorone diisocyanate 223 were placed. Parts, 0.1 part of dibutyltin dilaurate, and stirring under a nitrogen stream.
The mixture was heated to 100 ° C. and reacted for 5 hours to obtain an NCO group-terminated urethane prepolymer (NCO% 8.8%). A second liquid Y1 was prepared by further adding 5 parts of PBZ to 100 parts of the urethane prepolymer.

Production Example 4 87 parts of methyl ethyl ketone oxime was further added to 473 parts of the intermediate NCO-terminated urethane prepolymer in the reactor prepared in Production Example 3, and reacted at 60 to 80 ° C. for 3 hours. The external absorption spectrum confirmed that the isocyanate group had disappeared. A second liquid Y2 was prepared by further adding 5 parts of PBZ to 100 parts of the blocked urethane prepolymer.

Comparative Production Example 1 A first liquid X3 was prepared in the same manner as in Production Example 2, except that a methacrylic acid adduct of diethylene glycol diglycidyl ether was used instead of the reaction product of aniline and glycidyl methacrylate.

Examples 1 to 3 and Comparative Examples The first liquids X1 to X3 of Production Examples 1 and 2 and Comparative Production Examples and the second liquids Y1 and Y2 of Production Examples 3 and 4 were mixed at the mixing ratio shown in Table 1. Then, it was applied on a mild steel plate to a thickness of 30 μm using an applicator and baked at 120 ° C. for 20 minutes. Table 1 shows the evaluation results of the coating film hardness (pencil hardness).

[0038]

[Table 1]

Film hardness (pencil hardness: using Mitsubishi pencil)

[0040]

Since the baking-curable coating composition of the present invention does not contain an organic solvent, there are no problems such as the inhalation of solvent vapor by the human body, the danger of fire, and environmental pollution. In addition, the curing reaction is fast, and a hard coating film having excellent scratch resistance can be obtained. Furthermore, since the metal adhesion is good, it is useful as a paint for PCM.

Claims (3)

(57) [Claims] 1. (Meth) having a tertiary amino group and a hydroxyl group
Acrylic monomer (A), polyisocyanate compound (B), polyol (C), radical polymerization initiator (D)
A bake-curable coating composition comprising a pigment, if necessary. 2. The (meth) acrylic monomer (A)
Is an addition reaction product of glycidyl (meth) acrylate and a compound having a primary or secondary amino group.
The baking-curable coating composition according to the above. 3. The method according to claim 1, wherein the polyisocyanate compound (B) is
Aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, araliphatic polyisocyanate, modified products thereof (carbodiimide group, buret group, allophanate group, urea group, isocyanurate group, oxazoline group-containing modified product, Trimethylolpropane adducts) and their molecular weights of 50 to 5,000
The baking-curable coating composition according to claim 1 or 2, which is a blocked product of at least one polyisocyanate selected from the group consisting of an active hydrogen-containing compound and a urethane prepolymer having a terminal NCO group.