JP2585991B2 - Paint finishing method - Google Patents

Description

The present invention relates to a novel and useful paint finishing method,
In particular, the present invention relates to a paint finishing method using a combination of different kinds of resin compositions for a base coat paint and a top coat paint.

[Problems to be Solved by Conventional Techniques and Inventions] In recent years, plasticization of outer plates and parts has been rapidly expanding in the automobile industry. When the material is a steel plate, a high-temperature baking one-pack type paint using an aminoplast-based curing agent is usually adopted as a paint resin used. However, when the material itself is made of plastic, some materials have a low heat-resistant temperature, and a high-temperature baking type paint is additionally used for plastic.

In addition, in the method of finishing paint for automotive top coating, the base coat paint is also used in the so-called solid color paint finish method, in which not only the metallic paint finish method in which a paint containing a metallic powder is applied but also a paint in which a color pigment is blended. The effectiveness of a two-coat, one-bake finish method of applying a clear paint (including a colored paint that does not impair the transparency) after painting has been recognized.

That is, the coating film obtained by the two-coat, one-bake finish is excellent in finished appearance and feeling of holding, and the one-coat, one-bake metallic finish method has a remarkable defect in chemical resistance. One bake finish improves that drawback. Conventionally, solid color paints containing a vinyl polymer as a main component, in particular, have a remarkable defect in weather resistance. However, by using this two-coat, one-bake finishing method, a coating film having excellent weather resistance can be obtained. The two-coat, one-bake finish method has various advantages.

In general, the two-coat, one-bake coating finish method is to apply an aminoalkyd resin paint, a thermosetting acrylic resin paint, etc. as a base coat paint, apply the base coat, and leave it for 2 to 5 minutes to remove some solvent. After volatilization, the same kind of top coat paint is applied immediately, and then cured by baking for 20 to 30 minutes in an atmosphere at a temperature of 140 to 150 ° C. in a hot air drying oven. Here, as a source of hot air, heavy oil, propane gas, butane gas, city gas, or electric power is used, and two coats and one bake finish using a conventional thermosetting paint which is heated and cured at 140 to 150 ° C. The method has a disadvantage that the cost is increased due to consumed fuel and electric power.

As described above, in the method of coating finish for automotive top coating, from the viewpoint of energy saving and material replacement, coating workability, various physical properties, finished appearance, excellent weather resistance, etc., two coats using room temperature or low temperature curable resin, At present, there is a demand for rapid development of baking paints.

[Means for Solving the Problems] However, the present inventors have proposed a method for satisfying the aforementioned various requirements.
As a result of intensive studies to obtain a coating for 1-coat and 1-bake coating, it was found that the above-mentioned requirements were satisfied by using a specific composition combination as a combination of a base-coat coating and a top-coat coating. It has been completed.

That is, the present invention applies a paint (base coat) containing a curable resin containing a metallic powder and / or a coloring pigment as a main component, and then applies a clear paint (top coat) containing a curable resin as a main component on the painted surface. Paint)
Thereafter, in the coating finishing method of curing simultaneously, as the base coat paint and the top coat paint, either one of the following paint compositions is used, and the other paint is the following [II] paint composition. A paint finishing method characterized by using a resin composition for paint.

[I] (A): 1 to 100% by weight of a vinyl monomer having a polymerizable unsaturated group and at least one siloxy group in one molecule, and (B): a copolymerizable vinyl other than the above (A) A resin composition comprising a vinyl copolymer (I) comprising 99 to 0% by weight of a monomer, a polyisocyanate having a reactivity with a hydroxyl group formed from the polymer, and a dissociation accelerating catalyst.

[II] A resin composition obtained by blending a polyisocyanate with a vinyl polymer polyol or polyester polyol.

That is, the resin composition [I] is a vinyl polymer (I)
The siloxy groups in the polymer react with water in the air to form hydroxyl groups in the vinyl polymer (I), and the hydroxyl groups react with the polyisocyanate to form a strong coating film. The product [II] forms a strong coating film by a conventional curing reaction between a polyol and a polyisocyanate. When the resin composition [I] is used for a topcoat paint, a coating film having excellent gloss and finished appearance can be obtained. On the other hand, when the resin composition [I] is used as a base coating material, a coating film having excellent glitter and metal orientation can be obtained if the resin composition is a metallic coating material, and if the resin composition [I] is a solid color coating material, the coloring property can be improved. There is an advantage that a coating film excellent in the above is obtained. A paint finishing method using a combination of each paint using the above-described resin composition [I] and a base coat paint or a top coat paint using the resin composition [II] has room-temperature or low-temperature curability, The obtained composite coating film is excellent in various physical properties, finished appearance, gloss and the like.

Here, the vinyl-based monomer (A) constituting the vinyl-based polymer (I) includes a polymerizable unsaturated group and a siloxy group bonded to at least one or more carbon atoms represented by the following formula in one molecule. Is a vinyl monomer.

These vinyl monomers (A) include, for example, trialkylchlorosilane or triphenylchlorosilane, triallylchlorosilane, dialkylchlorosilane, etc. in the presence of a hydrochloric acid scavenger such as triethylamine or pyridine as described below. The product obtained by reacting with the hydroxyl group-containing vinyl monomer (b) is referred to, and typical examples thereof include trimethylsiloxyethyl (meth) acrylate, trimethylsiloxypropyl (meth) acrylate, and trimethylsiloxybutyl (meth). ) Acrylate, triethylsiloxyethyl (meth)
Examples include acrylate, tributylsiloxypropyl (meth) acrylate, and triphenylsiloxyalkyl (meth) acrylate. These can be used alone or as a mixture of two or more.

Further, as the hydroxyl group-containing vinyl monomer (b), β-hydroxyethyl (meth) acrylate, β-hydroxyethyl
Hydroxypropyl (meth) acrylate or β-
Hydroxyalkyl (meth) acrylates such as hydroxybutyl (meth) acrylate or N-methylolated (meth) acrylamide; β-hydroxyethyl (meth) acrylate to which ε-caprolactone is added [for example, Praclcel FM, FA series ( Daicel Chemical Industries, Ltd.) and TONE ^™ M-100 (manufactured by Union Carbide)]; Blenmer PP-1000 represented by the common name polypropylene glycol monomethacrylate and Blenmer PE series represented by the common name polyethylene glycol monomethacrylate (both Kyo Nippon Oil & Fats Co., Ltd.
Unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid or itaconic acid, and "Kajura E" (manufactured by Shinil Chemical Co., Ltd.), glycidyl ester of branched resin acid), octylic acid And adducts with monoepoxy compounds represented by monoglycidyl esters of monovalent carboxylic acids such as glycidyl ester or glycidyl coconut oil, or monoglycidyl ethers such as butyl glycidyl ether. is there. The amount of the vinyl monomer (A) used is preferably 1 to 100% by weight, and more preferably 5 to 90% by weight.
It is. If the amount is less than 1% by weight, the effect of the monomer cannot be expected.

Representative examples of the vinyl monomer (B) include an alkyl (meth) acrylate having an alkyl group having 1 to 22 carbon atoms in a side chain, styrene, vinyl toluene, t-butylstyrene, α-methylstyrene, and glycidyl. (meth) acrylate, 2-ethoxyethyl (meth) acrylate, (meth) acrylonitrile, cyclohexyl (meth) acrylate, diesters of maleic acid or fumaric acid with C ₁ -C ₁₈ comprising monohydric alcohols, N, N-dialkyl Examples include aminoalkyl (meth) acrylates or phosphoric acid group-containing (meth) acrylates, and vinyl-containing vinyl monomers such as vinyl acetate, hexafluoropropylene, and tetrafluoroethylene.

These vinyl monomers (B) can be used alone or as a mixture of two or more, depending on the desired coating film performance.

The vinyl polymer (I) constituting the composition of the present invention can be obtained by a known and common method using the above-mentioned monomers, for example, by a solution polymerization method using a radical generator. Can be.

As the radical generator, any one can be used as long as it is generally used for the polymerization of vinyl monomers.Among them, typical examples include azobisisobutyronitrile and di-tert-butyl. Examples of the solvent include aromatic hydrocarbons such as toluene and xylene; acetic acid esters such as ethyl acetate, butyl acetate and cellosolve acetate; and solvents such as methyl ethyl ketone and methyl isobutyl ketone. There are solvents such as ketones.

If necessary, mercaptans, α-methylstyrene and “dipentene T” (products of Nippon Terpene Chemical Co., Ltd.)
It is also possible to use a commonly used chain transfer agent such as, for example.

The vinyl polymer (I) thus obtained preferably has a number average molecular weight (n) of 500 to 50,000.

When n of the copolymer (I) is less than 500, the physical properties of the coating film cannot be sufficient, and the trialkylsiloxy group of the copolymer (I) is intended to exhibit the physical properties of the coating film. If the hydroxyl value (hereinafter, referred to as “OH value”) generated after liberation of the etc. is increased, the coating film becomes brittle, which is not preferable. Conversely, when it exceeds 50,000, the appearance of the coating film, It is not preferable because defects tend to appear in gloss, feeling of holding, painting workability, and the like.

Next, typical examples of polyisocyanates reactive with hydroxyl groups generated from the vinyl polymer (I) include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate or xylylene diisocyanate; tetramethylene diisocyanate; Aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexane diisocyanate; isophorone diisocyanate, methylcyclohexane-2,4- (or 2,6-) diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate) or 1,3-di (isocyanate Alicyclic diisocyanates such as methyl) -cyclohexane, and each of these diisocyanates, ethylene glycol, propylene glycol, neope Polyhydric alcohols such as tyl glycol or trimethylolpropane; extremely low molecular weight polyester resins having functional groups that react with isocyanate groups (including oil-modified types); or adducts with water and the like; Or a polymer (including oligomers) of the above-mentioned diisocyanates. Among these polyisocyanates, it is preferable to use a polyisocyanate prepolymer which is a reaction product of an aliphatic diisocyanate and a polyhydric alcohol in terms of weather resistance and low toxicity. The mixing ratio of these polyisocyanates to the above-mentioned vinyl polymer (I) is such that the range of OH group / NCO group = 1 / 0.5 to 1/3 (equivalent ratio) in terms of coating film performance. Is preferred.

When the vinyl polymer (I) of the present invention is exposed to the atmosphere, it is hydrolyzed by the reaction with moisture in the air to generate a hydroxyl group which can react with the polyisocyanate.

A catalyst must be used to promote this hydrolysis. Examples of the catalyst include phosphoric acid, phosphoric ester, phosphite, p-toluenesulfonic acid and amines thereof,
Acidic catalysts such as benzoic acid, trichloroacetic acid, trifluoroacetic acid, naphthalene disulfonic acid and amine salts thereof, ethylenediamine, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, butylamine, dibutylamine, t-butylamine, hexyl Amines such as amines and triethylamine; alkali catalysts such as potassium hydroxide, lithium hydroxide and sodium hydroxide; metal salts of carboxylic acids such as alkyl titanates, octylates, dibutyltin dilaurate, and lead octylate; monobutyl Compounds that generate fluorine ions, such as sulfide-type organic tin compounds such as tin sulfide and dioctyltin mercaptite, mercaptide-type organic tin compounds, and tetraethylammonium fluoride and cesium fluoride are effective. The amount of these curing catalysts to be added is 0.001 to 10% by weight, preferably 0.005 to 8% by weight, based on the vinyl polymer (I).

Further, since the composition of the present invention does not generate a hydroxyl group that can react with the curing agent unless exposed to the atmosphere, the composition of the present invention can be obtained as a one-pack type, highly stable coating composition.
However, in order to ensure long-term storage stability, it is sufficient to capture a small amount of water that enters for some reason. In other words, the addition of a water binder reactive with moisture ensures long-term stability. In addition, the water binder may be mixed in advance and used at the time of producing the vinyl copolymer (I). Examples of the water binding agent having reactivity with water include trimethyl orthoformate,
Trialkyl orthoformates such as triethyl orthoformate and tributyl orthoformate; trimethyl orthoacetate;
Trialkyl orthoacetates such as triethyl orthoacetate and tributyl orthoacetate; trialkyl orthoborates such as tributyl orthoborate and triethyl orthoborate; tetramethylsilicate, tetraethylsilicate, tetrabutylsilicate, tetra (2-methoxyethyl) silicate or Tetra (2-chloroethyl)
Tetra (substituted) alkyl silicates such as silicate alone; the same substance of the above tetra (substituted) alkyl silicates such as tetraphenyl silicate and tetrabenzyl silicate (hereinafter abbreviated as the same effective single substance); or dimer or trimer of tetraethyl silicate , Tetramer,
Hexamer, "Ethylsilicate 40" (product of Colcoat Co., Ltd., tetraethylsilicate tetramer, pentamer, mixture of hexamer), etc., each of the above tetra (substituted) alkyl silicates alone and condensation of the same effective silicates Phenyl isocyanate, p-chlorophenyl isocyanate, benzenesulfonyl isocyanate, p
-Toluenesulfonyl isocyanate, isocyanate ethyl methacrylate (Dow Chemical's NC
Compounds having an isocyanate group, such as an O group-containing monomer).

The amount to be used is 0.1% based on the vinyl copolymer (I).
1-30% by weight, preferably 0.5-20% by weight is good.

Next, the resin composition [II] which is an essential component of the present invention will be described. The vinyl polymer polyol is obtained by the above-mentioned ordinary polymerization method using the above-mentioned hydroxyl group-containing vinyl monomer (b) as essential and, if necessary, the above-mentioned vinyl monomer (B). On the other hand, polyester polyols are isophthalic acid as an acid component, phthalic anhydride,
Polybasic acids such as succinic anhydride, adipic acid and trimellitic anhydride, benzoic acid, monobasic acids such as para-t-butylbenzoic acid, neopentyl alcohol as an alcohol component,
Trimethylolethane, trimethylolpropane, 1,6
-It is appropriately synthesized using hexanediol, 1,5-pentanediol, pentaerythritol, glycerin, ethylene glycol and the like. The polyester polyol may be oil-modified, and usually has an oil length of 30% or less, and is a non-drying oil in terms of compatibility with the resin and weather resistance, especially coconut oil and its fatty acids, and synthetic fatty acids such as octylic acid. Alternatively, it can be obtained by using a monoglycidyl ester of a synthetic fatty acid such as Cardura E in combination.

Next, the above-mentioned polyisocyanates as curing agents may be used in the same ratio.

The resin composition of the present invention thus obtained is used as a paint for a top coat and a paint for a base coat in a two-coat, one-bake finishing method.

When used as a topcoat paint, it can be used as a clear paint as it is, but if necessary, a colored pigment or dye can also be used.

On the other hand, when used as a base coat paint, the composition of the present invention includes a commonly known metallic powder such as aluminum powder, copper powder, and mica powder, an inorganic pigment such as titanium oxide and calcium carbonate, and phthalocyanine blue, toluidine red, and benzidine yellow. An organic pigment such as the above may be blended, and a metallic paint or a solid color paint may be prepared by a known and commonly used coating method.

In addition, various conventional additives such as a leveling agent, an ultraviolet absorber, and a pigment dispersant may be used in the top coat paint and the base coat paint as needed.

Air spray coating or electrostatic spray coating is suitable for coating the top coat paint and the base coat paint using the composition of the present invention, and the dry film thickness of the top coat paint is 10 to 100 μm, preferably 10 to 100 μm. The coating may be carried out in the range of 60 μm and the dry film thickness of the base coat paint is in the range of 5 to 50 μm, preferably 8 to 20 μm.

Approximately 20 coating intervals between base coat and top coat
C. for 1 to 45 minutes, preferably 2 to 20 minutes. It is also possible to forcibly dry the base coat to shorten the coating time. After the coating film of the base coat is brought to a touch-dry or semi-cured dry state under the above-mentioned drying conditions, the top coat may be applied. After applying the top coat, it may be cured at a predetermined temperature and time. 60 ~
Forcibly drying at a temperature of 100 ° C for about 10 to 60 minutes is preferable in terms of curability and productivity, but the drying and curing conditions are appropriately changed according to the type and properties of the base coat paint and the top coat paint and the material. I can never do it.

As described above, the two-coat, one-bake finishing method using the composition of the present invention forms a composite cured coating film having excellent coating performance at room temperature or low-temperature heating drying below the heat resistance temperature of ordinary plastic materials. Thus, a coating film having physical properties comparable to those of conventional thermosetting acrylic resin paints and aminoalkyd resin paints can be obtained.

[Examples] Next, the present invention will be described in detail with reference to Production Examples and Examples. Hereinafter, all parts are by weight unless otherwise specified.

Production Example-1 [Preparation example of vinyl polymer (I)] 300 parts of trimethylsiloxyethyl methacrylate,
200 parts of styrene, 400 parts of n-butyl methacrylate and acrylic ester SL (C ₁₂ -C ₁₃ manufactured by Mitsubishi Rayon Co., Ltd.)
Of a monomer mixture consisting of 100 parts of a methacrylate having an alkyl group of the formula: 200 parts of toluene, 500 parts of toluene, 200 parts of isobutyl acetate, and azobisisobutyronitrile (AIB
N) 5 parts and tert-butyl perbenzoate (t-BP
B) Charge 10 parts into a four-necked flask equipped with a stirrer, an inert gas inlet, a thermometer and a cooler, hold at 90 ° C. for 1 hour, and then heat up to 115 ° C. over 30 minutes And at the same temperature, 300 parts of isobutyl acetate of 800 parts of the remaining monomer mixture,
A mixture consisting of 10 parts of t-BPB and 5 parts of AIBN was added dropwise over 3 hours, and the mixture was kept at the same temperature for 10 hours to obtain a nonvolatile matter (hereinafter abbreviated as NV) 49.8% and a viscosity (Gardner at 25 ° C). A resin solution having YZ, a number average molecular weight (hereinafter abbreviated as n) of 13000 and an OH value of 42 was obtained.

 Hereinafter, this resin solution is abbreviated as [I-1].

Production Example-2 [Id.] Triphenylsiloxyethyl methacrylate 250
Parts, methyl methacrylate 250 parts, styrene 150 parts, n
A resin was obtained in the same manner as in Production Example 1, except that 220 parts of -butyl methacrylate and 130 parts of n-butyl acrylate were used instead.

A resin solution having an NV of 49.1%, a viscosity of X, n of 1300 and an OH value of 18 was obtained.

 Hereinafter, this resin solution is abbreviated as [I-2].

Production Example-3 [Same as above] Resin was produced in the same manner as in Production Example-1 except that 135 parts of trimethylsiloxyethyl acrylate, 510 parts of methyl methacrylate, 350 parts of n-butyl methacrylate, and 5 parts of n-butyl acrylate were used instead. I got

It was a resin solution having an NV of 50.8%, a viscosity of Z, n of 15,000 and an OH value of 19.

 Hereinafter, this resin solution is abbreviated as [I-3].

Production Example-4 [Preparation Example of Vinyl Polymer Polyol] 310 parts of methyl methacrylate, 100 parts of ethyl methacrylate, 150 parts of ethyl acrylate, 216 parts of isobutyl methacrylate, 114 parts of β-hydroxyethyl methacrylate, 100 parts of styrene, A resin was obtained in the same manner as in Production Example 1, except that 10 parts of methacrylic acid was used instead.

The resin solution had an NV of 50.0%, a viscosity of Z, n of 15,000 and an OH value of 25.

 Hereinafter, this resin solution is abbreviated as [II-1].

Production Example-5 [Preparation Example of Polyester Polyol] In a reaction vessel equipped with a stirrer, a thermometer, and a water separator, 200 parts of isophthalic acid, 200 parts of phthalic acid, 237 parts of adipic acid, 365.3 parts of neopentyl glycol, and trimethylolpropane 1
24 parts were added, and the temperature was raised to 180 ° C. while heating and stirring. 180 ℃
To 230 ° C., the temperature was raised at a substantially constant rate in 5 hours, and then kept at 230 ° C. Further, 720 parts of xylol was gradually added to switch to the azeotropic condensation method. Reaction temperature 230
The acid value of the resin was monitored while keeping the temperature at ° C, and the reaction was terminated when the acid value reached 4.0. The resulting polyester polyol was oil-free with an OH value of 54, NV of about 60%, and n3000.

 Hereinafter, this resin solution is abbreviated as [II-2].

Examples 1 to 5 After separately preparing a top coat paint and a base coat paint by the usual coating method at the compounding ratio (parts by weight) shown in Table 1, xylene / toluene / ethyl acetate =
Diluted to a spray viscosity with a mixed solvent of 30/50/20 (weight ratio), and dried coatings of base coat paint and top coat paint on zinc phosphated steel sheet were 15μm and 20μ respectively.
m, and the coating interval between the two paints was set to 2 minutes by air spraying, and the coating was heated at 60 ° C. for 30 minutes to obtain a cured coating film. Table 1 shows the results of evaluation of the physical properties of each of the coating films thus obtained. The physical properties were evaluated after being left at room temperature for 3 days after forced drying.

Evaluation method ◎… Excellent [Effects of the Invention] As described above, the composition used in the method of the present invention has two coats which are excellent in coating workability and low-temperature curability as compared with conventional amino alkyd resin paints and thermosetting acrylic resin paints. This is a 1-baked paint, and the resulting coating film has extremely practical physical properties.

Continuation of the front page (56) References JP-A-58-76469 (JP, A) JP-A-62-253670 (JP, A) JP-A-58-225155 (JP, A) JP-A-53-61694 (JP) JP-A-60-92365 (JP, A) JP-A-55-129462 (JP, A) JP-B-6-78499 (JP, B2)

Claims (1)

(57) [Claims] 1. A paint (base coat) mainly composed of a curable resin containing a metallic powder and / or a color pigment is applied, and then a clear paint (top coat mainly composed of a curable resin) is applied to the painted surface. ), And then simultaneously cured, as the base coat paint and the top coat paint,
A paint finishing method, wherein a paint resin composition of the following [I] is used for one of the paints, and a paint resin composition of the following [II] is used for the other paint. [I] (A): 1 to 100% by weight of a vinyl monomer having a polymerizable unsaturated group and at least one siloxy group in one molecule, and (B): a copolymerizable vinyl other than the above (A) A resin composition comprising a vinyl copolymer (I) comprising 99 to 0% by weight of a monomer, a polyisocyanate having a reactivity with a hydroxyl group formed from the polymer, and a dissociation accelerating catalyst. [II] A resin composition obtained by blending a polyisocyanate with a vinyl polymer polyol or polyester polyol.