JP3386910B2 - Pigment dispersion composition for colored electrodeposition coating - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention relates to a pigment dispersion composition for colored electrodeposition coating.

[0002]

2. Description of the Related Art Regarding electrodeposition coating, various proposals have been made for the purpose of improving adhesion to a coated object and coloring. Japanese Patent Laid-Open No. 50-
No. 1137, Japanese Patent Laid-Open No. S60-36796 and Japanese Patent Laid-Open No. S60-60
Japanese Laid-Open Patent Publication No. 4-124298 proposes the above-mentioned method.
It is not yet sufficient as described in Japanese Patent No. 154999.

JP-A-4-154999 discloses that by coating an acrylic polymer or a copolymer on the surface of particles of an organic pigment, the dispersibility in the coating composition is improved and the sharpness and the preservation of the electrodeposition coating film are improved. It is proposed that the colorability, transparency, and weather resistance can be improved, and workability, designability, and coating film performance can be improved.

That is, Japanese Patent Laid-Open No. 4-154999 discloses
By using an organic pigment that has a lighter specific gravity than conventional inorganic pigments, it is possible to improve workability, such as eliminating the need to constantly stir the coloring tank compared to when using inorganic pigments, and to improve the designability of the inorganic pigments. Improvements etc. are written.

[0005]

However, the occurrence of color unevenness during baking and curing is prevented, and the pigment particles are prevented from settling even if the coloring tank is left without stirring for a long time. In order to prevent separation from the coating emulsion particles, it is necessary that both particles have very good compatibility in the dispersion medium and dispersibility of the pigment. Not to mention the sedimentation of the pigment in the coloring dispersion itself, if the dispersibility is poor, the pigment will precipitate in the dispersion during long-term storage, resulting in poor workability.

In this respect, the invention of JP-A-4-154999 is not sufficient, and it is necessary to improve the dispersibility of the pigment and the compatibility with the electrodeposition coating emulsion particles. An object of the present invention is to provide a pigment dispersion composition for colored electrodeposition coating which is excellent in dispersibility of the pigment and compatibility between the pigment particles and the electrodeposition coating emulsion particles in the dispersion medium.

[0007]

In the dry powder state, the particles of the pigment are agglomerated with each other, but it is necessary to make them very fine particles in order to improve the dispersibility. The particle size of the dispersion is about 0.6 μ or less, preferably 0.3
If it is less than μ, there is no aggregation or settling of the pigment even if left for 1 month, and even if it is mixed with the electrodeposition coating emulsion, even if left for 1 month without stirring, significant settling etc. is recognized in the electrodeposition tank. It was found that the long-term dispersion stability was maintained.

A dispersant for dispersing hydrophobic pigment particles in water is very important for obtaining good dispersibility. As a result of repeated studies on this, it was found that a polymer containing styrene is effective for dispersion and atomization of the organic pigment, and has good compatibility with the emulsion particles of electrodeposition coating composition.

This is because the phenyl group introduced into the copolymer by styrene is lipophilic, so that the pigment and emulsion particles and the copolymer do not repel each other and are dispersed.
It seems to improve the compatibility.

Monomers copolymerizable with styrene or a styrene derivative such as α-methylstyrene include α, β-ethylenic monomers such as vinyl chloride, vinyl acetate and acrylic acid, derivatives thereof, and anhydrous mylene. A monomer containing at least one of an acid and its derivative can be used.

Monomers mixed in styrene or a styrene derivative are mixed mainly for the purpose of water-solubilizing the polymer.
In order to introduce a more hydrophilic portion, it is desirable to introduce a carboxylic acid group, a sulfonic acid group or a hydroxyl group into the polymer. When the monomer in the copolymer has many hydroxyl groups, sodium sulfonate groups, etc., it may be water-soluble as it is.

The introduction of the hydroxyl group is carried out by using acrylic acid 2-
It can be obtained by using hydroxyethyl as the above-mentioned monomer or by saponifying a polymer into which vinyl acetate is introduced. The sodium sulfonate group may be polymerized using monomers such as sodium allyl sulfonate, sodium methallyl sulfonate, and sodium styrene sulfonate.

The introduction of the carboxylic acid group can be made water-soluble by polymerizing a monomer having a carboxylic acid group such as acrylic acid and maleic anhydride, and then neutralizing it by adding caustic soda, ammonia and an amine derivative. If the organic solvent used for the above-mentioned polymer synthesis is water-soluble, it is not always necessary to completely remove it. In this way, by dispersing the pigment with the copolymer in which the hydrophilic water-solubilizing group is introduced into the styrene copolymer, the pigment particles after dispersion have the hydrophobic electrodeposition coating emulsion particles and the dispersion medium water. It is possible to prepare a coloring liquid that has an affinity for both and is extremely compatible.

The weight average molecular weight of the copolymer used for dispersing the organic pigment is preferably 5,000 to 500,000. The molecular weight can be controlled by the amount of the polymerization initiator, the polymerization temperature and the like.

When the molecular weight of the copolymer is less than 5,000, a large amount of water-insoluble matter remains and the dispersion stability of the pigment is poor. On the other hand, when it exceeds 500,000, there are problems that the viscosity of the dispersion is excessively increased and that the dispersion of the pigment does not become fine particles.

On the other hand, when the weight average molecular weight of the copolymer is in the range of 5,000 to 500,000, the viscosity is low and the particle size is 0.3 μm or less with the addition amount of 10 wt% to 100 wt% of the pigment. A dispersion having good properties was obtained.

Organic pigments having excellent light resistance that can be used include phthalocyanine pigments, dioxazine pigments,
Fused polycyclic pigments such as indanthrene-based pigments, isoindolinone-based pigments, diketopyrrolopyrrole-based pigments, quinacridone-based pigments, perylene-based pigments, and anthraquinone-based pigments are preferably used, but versatile and versatile colors are available. You can use azo pigments you have without exception.

A white organic pigment (trade name "Shigenox" manufactured by Hakkor Chemical Co., Ltd.) was also examined, but it can be suitably used similarly to a colored organic pigment.

As a method for dispersing the pigment, a conventionally used ball mill, sand mill, roll mill or the like is preferably used. During the dispersion, for adjusting the volatilization rate of the coloring bath or the solvent of the coloring matter, alcohols such as methanol and ethanol, glycols such as ethylene glycol and propylene glycol and esters thereof, and water-soluble organic solvents such as alkanolamine are preferable. Used for. Various surfactants may be used for adjusting the coloring bath of the dispersion or the surface tension of the colored product.

The electrodeposition paint to be mixed with the pigment dispersion of the present invention may be an anionic paint, typically an acrylic resin.
Examples include melamine emulsion paints and fluorine-melamine emulsion paints.

The resin content in the electrodeposition paint is 5-40w
t% is preferable, and in the case of coloring, it is preferable to add the present dispersion so that the pigment concentration is 0.5 to 20 wt%, but the amount of the pigment electrodeposited on the coating film changes depending on the addition amount. It is possible to adjust the color.

[0022]

The present invention is a colored electrodeposition coating in which an organic pigment is dispersed in water or water containing a water-soluble organic solvent with a copolymer of two or more monomers containing styrene or its derivative or a modified product thereof. Since it is a pigment dispersion composition for use in the present invention, it works effectively for dispersion and atomization of the organic pigment, and the compatibility with the emulsion particles for electrodeposition coating composition is improved.

When α, β-ethylenic monomer and / or its derivative or maleic anhydride and / or its derivative are used as a monomer mixed with styrene or its derivative, the copolymer is water-soluble. And dispersion stability is improved.

If the weight average molecular weight of the copolymer is adjusted to be in the range of 5,000 to 500,000, 10 wt% to 1% of the pigment is used.
With the addition amount of 00 wt%, a dispersion having a low viscosity and having a fine particle size of 0.3 μm or less and good stability can be obtained.

[0025]

EXAMPLES Various pigment dispersion resins (copolymers) were synthesized under the conditions shown in Table 1, and pigment dispersion compositions were prepared under the compounding conditions shown in Table 2. Was actually electrodeposited to evaluate the state of the electrodeposition tank and the color unevenness after baking.

(Synthesis of Resin for Pigment Dispersion) The composition of the monomer and the polymerization initiator shown in Table 1 is 80 to 80 with butyl cellosolve, diosaquine, and tetrahydrofuran (THF) as a solvent.
The reaction was carried out at 150 ° C. by a normal solution polymerization method (dropping method), and the reprecipitated product in hexane was filtered and dried to obtain a resin (copolymer) solid.

The solid matter was neutralized and dissolved in water with a predetermined water-solubilizing agent to prepare 6 types of resin aqueous solutions having a resin content of 30%.

[0028]

[Table 1]

(Preparation of Pigment Dispersion) Pigment dispersions were prepared at the compounding ratios shown in Table 2 below.

[0030]

[Table 2]

In Table 2, 1) Dainippon Ink, phthalocyanine pigment 2) Ciba Geigy, diketopyrrolopyrrole pigment 3) Ciba Geigy, isoindolinone pigment 4) Hacole Chemical, white organic pigment 5) The pigment concentration was diluted to 10% and measured after sharpless treatment. 6) The sample was sealed in a closed test tube, left for 1 month, and then the thickness of the precipitate was evaluated. Ο: Not confirmed, Δ: less than 5 mm, ×: 5 mm or more

The pigment dispersion was prepared by a bead mill, and the compounding at that time and its characteristics are also shown in Table 2.

(Electrodeposition test) An aluminum plate treated to have an anodized film having a thickness of 9 μm was used as an anode, and a carbon rod was arranged as a cathode in an electrodeposition tank. Was filled with both solutions to be 1%.
After energizing with a DC voltage of 120 V for 5 minutes, the aluminum plate was baked at 180 ° C. for 30 minutes to complete the coating.

The state at this time is shown in Table 3.

[0035]

[Table 3]

As is clear from Tables 2 and 3, the pigment dispersion composition of the present invention can be used for a long period of time by mixing it with an electrodeposition paint without causing the pigment to settle even when left standing for a long time. Even if the electrodeposition liquid is not uniform. Further, it was confirmed that even after baking, the compatibility between the emulsion particles and the pigment in the electrodeposition coating was improved, so that the color unevenness of the coating film did not occur. Further, the weight average molecular weight of the copolymer is 5
When it exceeds 0,000, the initial particle diameter of the pigment particles exceeds 0.6 μ as seen in Dispersion 5, but when the weight average molecular weight of the copolymer is 500,000 or less, the pigment particles are It can be seen that the initial particle diameter of is less than 0.6 μm and the long-term dispersion stability is maintained. It was also found that particularly when the initial particle size of the pigment particles is 0.3 μm or less, a dispersion in which the pigment is atomized and has good long-term dispersion stability can be obtained.

[0037]

Industrial Applicability The present invention provides a coloring charge obtained by dispersing an organic pigment in water or water containing a water-soluble organic solvent with a copolymer of two or more kinds of monomers containing styrene or a derivative thereof or a modified product thereof. Since it is a pigment dispersion composition for electrodeposition coating, the dispersibility of the pigment and the compatibility of the pigment particles in the dispersion medium and the electrodeposition coating emulsion particles are excellent, preventing the occurrence of color unevenness during baking and curing. In addition, the pigment particles are prevented from settling out even if the coloring tank is left without stirring for a long period of time, and the pigment particles and the electrodeposition coating emulsion particles are not separated.

Continuation of the front page (56) Reference JP-A-6-93215 (JP, A) JP-A-3-103479 (JP, A) JP-A-58-40362 (JP, A) JP-A-56-47412 (JP , A) JP 60-81263 (JP, A) JP 59-33368 (JP, A) JP 48-51930 (JP, A) JP 48-26825 (JP, A) JP 47-6279 (JP, B1) JP-B-45-24222 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 5/44 C09D 17/00 C09B 67/20

Claims (4)

(57) [Claims] 1. An organic pigment and a dispersion medium containing the organic pigment in a dispersion composition and in an electrodeposition bath.
Electrodeposition coating containing a dispersant to be dispersed in water and water or water containing a water-soluble organic solvent
An organic pigment dispersion composition for wearing, wherein the dispersant comprises styrene or a derivative thereof as a lipophilic monomer unit, and one or more monomers (polyoxyalkylene glycol or a polyoxyalkylene glycol thereof) capable of being polymerized therewith. Any of a carboxylic acid group, a sulfonic acid group, and a hydroxyl group copolymerized with a monoether derivative-modified vinyl monomer and a vinyl monomer having a C ₈ or more alkyl group)
Is a copolymer having a weight average molecular weight of at least 5,000 or more and not more than 500,000 or a modified product thereof, wherein the organic pigment is added to the water of the pigment dispersion composition or the water containing a water-soluble organic solvent by the dispersant It is dispersed, and the copolymer or the modified product thereof is added to the organic pigment.
10 to 100% by weight of the organic pigment particles
A pigment dispersion composition for colored electrodeposition coating, which is finely divided into particles having a diameter of 0.3 μm or less . 2. The monomer is vinyl chloride, vinyl acetate,
Acrylic acid, their derivatives, maleic anhydride, its
2. At least one of any of the derivatives.
2. The pigment dispersion composition for colored electrodeposition coating of. 3. The monomer is 2-hydroxy acrylate.
The pigment dispersion for colored electrodeposition coating according to claim 1, which contains ethyl.
Composition. 4. An electrodeposition paint is added to water as a dispersion medium in an electrodeposition bath.
In addition, the particle size was reduced to 0.6 μm or less.
A machine pigment is dispersed by the dispersant according to claim 1.
In this electrodeposition bath, place an aluminum plate on the anode.
Colored electrodeposition coating method characterized by being energized for electrodeposition coating
Law.