JP2682044B2 - Matte electrodeposition coating composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coating composition for electrodeposition coating, and in particular to obtain a matte coating film excellent in adhesiveness and coating film properties by coating anion electrodeposition coating composition. Coating composition.

[Prior Art] Various compositions and coating methods have been conventionally proposed for matte electrodeposition coating. Regarding the resin composition, for example, JP-A-56-106977 proposes a method of adding an organic sulfonic acid or a sulfuric ester to an amino resin curable anionic electrodeposition coating composition. In addition, the inventors of the present invention, in Japanese Patent Application No. Sho 61-187836 (Japanese Patent Laid-Open No. 63-43975), describe a basic nitrogen-containing acrylic monomer, an ethylenically unsaturated organic carboxylic acid, a hydroxyl group-containing acrylic monomer. A matte electrodeposition composition comprising an acrylic copolymer as an essential component, an amino resin, and an organic sulfonic acid compound is proposed.

[Problems to be Solved by the Invention] However, in the former method, the organic sulfonic acid compound is used as a curing accelerator for the amino resin itself and the amino resin and a compound having an OH group (acrylic copolymer in this method). Since it works, there is a tendency for curing to proceed excessively under normal baking conditions (160 to 200 ° C, 20 to 1 hour). By the way, when a normal plate on a metal plate, or an aluminum base material that has undergone alumite treatment, is scraped off with a sharp knife, the coating film is scraped continuously or in a state close to continuous, but in this method, The coating film in which the addition amount of the organic sulfone compound was increased to obtain a low gloss is not scraped continuously in such a test, but scatters as a powder. Further, depending on the type and amount of the organic sulfonic acid added, the adhesion to the base material is poor, and the phenomenon occurs that the base material and the coating film are separated by the cellophane tape. These properties are due to, for example, when the electrode sash coated with aluminum and other members are used by cutting or punching, if the coating is not flexible, the coating partially peels off at the cut end, It is not preferable because the material may be exposed.

An object of the present invention is to provide a coating composition capable of obtaining a matte electrodeposition coating film having improved adhesiveness and coating film physical properties, particularly flexibility of the coating film.

[Means for Solving Problems] The purpose of the present invention is as follows. (A) A. Ethylenically unsaturated carboxylic acid 3 to 20% by weight B. Hydroxyl group-containing acrylic monomer 1 to 30% by weight CA and B Acrylic copolymer obtained by copolymerizing 96 to 50% by weight of other monomer copolymerizable with or amine or its neutralized product 80 to 30 parts by weight (B) Amino resin 20 to 70 parts by weight Part (c) Hydroxyl group-containing organic compound having a number average molecular weight of 300 to 5000
3 to 20 parts by weight (d) A coating composition for a matte electrodeposition coating comprising 0.1 to 3 parts by weight of an organic sulfonic acid or a neutralized product thereof.

 Hereinafter, the present invention will be described in detail.

As the (A) ethylenically unsaturated carboxylic acid, one or more kinds of acrylic acid, methacrylic acid, crotonic acid, vinylacetic acid, itaconic acid, maleic acid and the like are preferably used. When these are copolymerized with an acrylic copolymer, at least a part thereof is neutralized with an amine and / or another alkaline substance, thereby imparting water solubility or water dispersibility to the copolymer. In addition to making it possible to use as anion electrodeposition paint,
It serves as an accelerator for the curing reaction between the amino resin (b) itself and the amino resin and the hydroxyl group of the acrylic copolymer.

The amount of ethylenically unsaturated carboxylic acid used is 3 to 20% by weight, preferably 4 to 15% by weight, based on the total monomers. When the amount used is less than 3% by weight, the water-solubilizing ability or water-dispersing ability of the acrylic copolymer is insufficient. On the other hand, if it exceeds 20% by weight, after electrodeposition coating, the coating film may be redissolved or the coating film may be roughened, and the coating film appearance may be deteriorated.

As the acrylic monomer having an OH group (B), one or more of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and the like are preferably used. By introducing a hydroxyl group into the acrylic copolymer, the acrylic copolymer and the amino resin undergo a crosslinking reaction by heating, and the chemical resistance, stain resistance and hardness of the coating film can be improved. The hydroxyl group-containing acrylic monomer is used in an amount of 1 to 30% by weight based on all monomers. It is more preferably 5 to 20% by weight. If the amount of this monomer is less than 1% by weight, the crosslinking with the amino resin is not sufficient, and the physical properties of the coating film such as chemical resistance, stain resistance and hardness are not sufficient. Corrosion resistance is deteriorated, the smoothness of the coating film is lost, and the appearance is deteriorated, reducing the commercial value.

As the monomer (B) copolymerizable with A and B of C, any monomer copolymerizable with A and B by a conventional method can be used. For example, acrylic acid or methacrylic acid and acrylic acid ester formed by monohydric alcohol, or methacrylic acid ester, styrene, vinyltoluene,
vinyl compounds such as α-methylstyrene and vinyl acetate,
One or more of acrylonitrile, acrylamide, methacrylamide, etc. are used.

Further, it is considered that when a basic nitrogen-containing acrylic monomer is copolymerized as the copolymerizable monomer, it has an effect of capturing the added organic sulfonic acid, and a matte coating having a low gloss value. In order to obtain The basic nitrogen-containing acrylic monomer is preferably copolymerized at 0.05 to 10% by weight, particularly 0.1 to 3% by weight.

Examples of the basic nitrogen-containing acrylic monomer include aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, di-n-propyl (or isopropyl) aminoethyl (meth) acrylate, and di-n-.
Acrylic ester derivative or methacrylic ester derivative such as butyl (or isobutyl or t-butyl) aminoethyl (meth) acrylate, aminoethyl (meth) acrylamide, N-dimethylaminoethyl (meth) acrylamide, N-diethylaminoethyl ( (Meth) acrylamide, N-di-n-propyl (or isopropyl) aminoethyl (meth) acrylamide,
An acrylamide derivative represented by N-di-n-butyl (or isobutyl, or t-butyl) aminoethyl (meth) acrylamide, or a methacrylamide derivative is preferably used.

The molecular weight of the acrylic copolymer (a) is selected in a wide range according to the requirement of matting properties, but the larger the molecular weight, the greater the matting effect. The weight average molecular weight is preferably 10,000 to 100,000.

It is possible to obtain an acrylic copolymer suitable for the present invention by polymerizing the monomers A to C by a known method. For example, the monomers A to C are alcohol-based such as n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, ethyl cellosolve, propyl cellosolve, butyl cellosolve, ethyl diglycol and butyl diglycol. It is possible to preferably perform copolymerization by using a polymerization initiator such as azobisisobutyronitrile or benzoyl peroxide in one or more solvents. Further, the acrylic copolymer is prepared by using one or more alkaline substances such as amine compounds, ammonia, alkali metal hydroxides and alkaline earth metal hydroxides.
It is preferable that the carboxylic acid possessed by this copolymer is partially or completely neutralized and then water-soluble or water-dispersed. The neutralization method may be carried out at the monomer stage before the polymerization, but it is more preferable to neutralize after the polymerization because the influence of the alkaline substance on the polymerizability of the monomer is small. In addition, after mixing this copolymer with the amino resin (b), the hydroxyl group-containing organic compound (c), the organic sulfonic acid (d) or its neutralized product in an unneutralized state, The addition does not hinder the effects of the present invention.

The amino resin (b) is, for example, a melamine resin, a benzoguanamine resin, an acetoguanamine resin, a urea resin or the like which has been used as a conventionally known curing agent, an acrylic copolymer resin (a) and / or a hydroxyl group (c). Any one can be used as long as it reacts with the hydroxyl group of the contained organic compound. Melamine resins and benzoguanamine resins are preferably used, but those modified as a curing agent for paints are generally preferable. For example, most or most of the nitrogen atoms of melamine and benzoguanamine are methylol group, methoxymethyl group, ethoxymethyl group, n-propylmethyl group, isopropylmethyl group, n-butoxymethyl group, isobutoxymethyl group, t-butoxymethyl group. , Butoxyethoxymethyl group, carboxylalkoxymethyl group and the like are preferably used.

The ratio of the acrylic copolymer (a) to the amino resin (b) is 8: 2 to 3: 7, preferably 8: 2 to 4: 6 in terms of solid content. (B) When the amino resin content is less than 2, gloss is exhibited and a preferable matte coating film cannot be obtained, sufficient curing cannot be obtained, and chemical resistance and the like decrease. (B) When the amount of amino resin exceeds 7, even if the hydroxyl group-containing organic compound (c) is added, problems occur in adhesiveness and flexibility of the coating film.

(C) a hydroxyl group-containing organic compound having a molecular weight of 300 to 5000 is, for example, a natural oil or fat having a hydroxyl group represented by castor oil, ethylene glycol, glycerol,
One or more compounds having two or more hydroxyl groups such as trimethylolpropane and pentaerythritol, and
Dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, lactic acid, γ-oxybutyric acid, oxycarboxylic acids such as δ-oxysuccinic acid, γ-butyrolactone, ε-caprolactone, etc. OH group-containing polyesters obtained by the reaction of one or more of the above lactones, one or more polyether compounds of the above and, for example, ethylene glycol, propylene glycol, tetramethylene glycol, and OH at the end Polycarbonate having two or more groups is preferably used.

The compound has one or more hydroxyl groups, preferably two or more hydroxyl groups, which react with the amino resin to be fixed in the coating film. In the case of a compound having no hydroxyl group, it tends to bleed out from the coating film over time, causing stickiness, and the softening effect also decreases.

The number average molecular weight of the compound is 300 to 5000, preferably 500 to 3000. When the number average molecular weight is less than 300, a part of the number average molecular weight evaporates when the coating film is dried and the addition effect is lost, and even if it remains, the adhesiveness and the flexibility imparting effect of the coating film are not sufficient. When the number average molecular weight exceeds 5,000, it is separated from the electrodeposition coating liquid and cannot enter the electrodeposition coating film. That is, this compound does not dissolve in water because it does not have a water-solubilizing ability, but it is apparently dissolved or dispersed by being wrapped in an acrylic copolymer, but when the molecular weight becomes 5000 or more, the acrylic copolymer The wrapping effect of the
Separate from the electrodeposition solution.

Since the compound has a low molecular weight in the coating film, it exerts the effect of one kind of plasticizer and imparts flexibility to the coating film in the coating film composed of the acrylic copolymer and the amino resin. Therefore, it is possible to prevent the powder from becoming powdery when the coating film is scraped off from the substrate with a knife. Further, the adhesiveness with the coating film is also improved. In addition, addition of the compound does not increase the gloss of the coating film, and the polyester compound tends to lower the gloss, which is effective in reducing the addition amount of the sulfonic acid compound (d). . Furthermore, the addition of the compound gives a desirable matte coating appearance with less skin roughness, less uneven gloss, and depth. 3 to 20 parts by weight of the compound,
Preferably 5 to 15 parts by weight are used.

The organic sulfonic acid of (d) or a neutralized product thereof can be any organic compound having a sulfonic acid group, but is preferably a compound represented by the general formula (R = C _{1 to} C ₁₈ alkyl group) (R ₁ and R ₂ = C _{1 to} C ₁₈ alkyl group) (R = C _{1 to} C ₁₂ alkyl group) (R ₁ , R ₂ = C ₁ -C ₁₂ alkyl group) and (R ₁ , R ₂ = C ₁ -C ₁₂ alkyl group) and the like are applicable. For example, p-toluenesulfonic acid, n-dodecylbenzenesulfonic acid, n-dibutylbenzenesulfonic acid, isopropylnaphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid and the like are used.

The amount of one or more of these used is 0.1 to 3% by weight, preferably 0.2 to 2% by weight, based on the total (solid content weight) of the acrylic resin (I) and the melamine resin. If it is less than 0.1%, gloss is produced and the matte effect is not sufficient, and if it exceeds 3%, the appearance of the coating film deteriorates (rough skin phenomenon), and even if the compound of (C) is added, a sufficient coating film cannot be obtained. The flexibility and adhesiveness cannot be obtained. These organic sulfonic acids can be added directly, but are preferably used in the form of an aqueous solution after being dissolved in water and at least partially neutralized with an amine such as triethylamine. The timing of adding and using these is not limited, and the acrylic copolymer (I) may be directly added to the acrylic copolymer (I) or after mixing the acrylic copolymer (I) with an amino resin, or the acrylic copolymer (I). After mixing the amino resin hydroxyl group-containing compound with
Alternatively, it can be added to the above mixture after being diluted with deionized water to a solid content concentration of 5 to 15%.

It is particularly preferable that the coating composition of the present invention is electrodeposited on an alumite-treated aluminum-based substrate without adding a pigment. It does not matter if a pigment and a solvent according to a conventional method and / or other additives which do not impair the effects of the present invention are blended and used.

Further, as the article to be coated, in addition to the aluminum-based material, any conductive material such as a chemical-treated iron-based material, stainless steel material, iron-zinc-based material, or plastic-plated material can be used.

EXAMPLES Next, the present invention will be described based on examples.

Examples 1 to 5 The monomers shown in A, B and C of Table 1 and azobisisobutyronitrile were dropped into each solvent of A, B and C of Table 1 at 80 to 92 ° C. over 4 hours. To do. Further, after 1 hour at 80 to 90 ° C., azobisisobutyronitrile was added 5 times at intervals of 30 minutes each in the amounts shown in A, B and C of Table 1,
Polymerization is carried out by keeping the temperature at 80 to 90 ° C for 1 hour. Then, the amounts of isopropyl alcohol, triethylamine and deionized water shown in Table 1 were added and stirred for about 30 minutes to obtain a water-dispersible or water-soluble acrylic copolymer. The viscosity (Gardner bubble viscometer, 25 ° C.) and solid content were as shown in Table 1.

The above acrylic copolymer (calculated as 45% solids)
Castor oil or "Plaxel" 308 (manufactured by Daicel Chemical Industries, Ltd., polyester polyol, molecular weight about 850, O
H value 198.8KOHmg / g), "Nikarac" MX-40 (solid content 100g)
(Calculated as) (Melamine resin manufactured by Sanwa Chemical Co., Ltd.) is mixed, and deionized water is added and dissolved. Furthermore, a triethylamine neutralized product of dinonylnaphthalenedisulfonic acid is added to make a matte anti-wear coating. Table 2 shows these mixed formulations. The coating material thus obtained was transferred to a stainless beaker, and subjected to alumite treatment and AC coloring treatment by a conventional method in a 12 cm × 5 cm × 1 mm aluminum base material (aluminum base material A-1100, alumite film thickness 9 μm, (Dense bronze color) was dipped, the anode terminal was connected to this, and the cathode terminal was connected to a stainless beaker, and electrodeposition coating was performed. After washing with water, baking was performed at 180 ° C. for 30 minutes, and then evaluation was performed. Table 2 shows the electrodeposition conditions, the film thickness and the evaluation results. As a result, it was found that both the paint containing castor oil and "Plaxel" 308 gave a good matte coating surface, and the coating film had excellent flexibility and adhesiveness. In addition, it was found that the gloss of "Plaxel" 308 in the additive-based paint was lower than that of the additive-free paint shown in Comparative Example (described later).

Comparative Examples 1 to 3 The acrylic resin copolymerizations of A, B and C in Table 1 were used to prepare the bath paints in Table 3 (that is, Comparative Examples 1 to 3) were the coating compositions of Examples 1 to 5. From castor oil and "plaxel". ).

The manufacturing method, the electrodeposition method, and the baking conditions were the same as in the example. Table 3 shows the results. As a result, Examples 1 to 5
It turns out that it is less flexible than that.

EFFECT OF THE INVENTION The matte electrodeposition coating composition of the present invention comprises (a),
Since it contains (b) and (d), a matte coating film can be obtained all at once by the usual electrodeposition coating method without increasing the number of processes for matting. No gloss unevenness and less rough skin. A uniform matte coating is obtained.

Depending on the amount of organic sulfonic acid, a coating film having a desired gloss can be obtained in a wide range. Therefore, in addition to the effect that the control of gloss is easy, that is, the bath management is easy, the coating composition for matte electrodeposition coating of the present invention further contains (c), so that the adhesiveness of the coating film is improved. Since it is good and has flexibility, the coating film on that part does not chip off or peel off during cutting and drilling. Also, by adding a compound having a hydroxyl group, which is difficult to peel off due to impact, a deep and elegant matte surface can be obtained.

In particular, in the case of a polyester-based hydroxyl group-containing compound, the gloss tends to be lower than in the case where it is not added, so that the addition amount of the sulfonic acid compound can be small. Therefore, an excellent effect such as the reduction of adverse effects (for example, deterioration of flexibility) caused by the sulfonic acid compound is produced.

Claims (1)

(57) [Claims] 1. A) Ethylenically unsaturated carboxylic acid 3 to 20% by weight B. Hydroxyl group-containing acrylic monomer 1 to 30% by weight Other monomers copolymerizable with CA and B 96 to 96% Acrylic copolymer obtained by copolymerizing 50% by weight or amine or its neutralized product 80 to 30 parts by weight (b) Amino resin 20 to 70 parts by weight (c) Hydroxyl group with number average molecular weight of 300 to 5000 Organic compound 3 to 20 parts by weight (d) Matte electrodeposition coating composition comprising 0.1 to 3 parts by weight of organic sulfonic acid or its neutralized product.