JP5283329B2 - Anionic electrodeposition paint with excellent scratch resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anionic electrodeposition coating giving both coating film appearance and coating film performance suitable to aluminum materials, and being excellent in scratch resistance in particular. <P>SOLUTION: The anionic electrodeposition coating comprises (A) a vinyl copolymer being prepared by the copolymerization of an &alpha;,&beta;-ethylenically unsaturated carboxylic acid monomer, a hydroxyl-containing &alpha;,&beta;-ethylenically unsaturated monomer and another &alpha;,&beta;-ethylenically unsaturated monomer, and having an acid value of 10-150 KOHmg/g-resin solid content and a hydroxyl value of 20-200 KOHmg/g-resin solid content, (B) an amino resin and (C) dimethylpolysiloxane-based silicone resin particles. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an anionic electrodeposition paint. More specifically, it is characterized in that it can provide a coating film excellent in scratch resistance, and is particularly suitable for the coating of an aluminum material.

  Anodized aluminum materials are lightweight, strong, and have excellent corrosion resistance, so they are widely used in building materials such as window frames, doors, and exteriors of buildings and houses. An anionic electrodeposition coating with a single coat and good finish is generally used for coating an aluminum material. A typical example of such an anionic electrodeposition coating is a melamine curable electrodeposition coating, which is prepared by blending a water-based acrylic resin containing a carboxyl group and a hydroxyl group with a melamine resin crosslinking agent and dispersing it in water. Painting and matte-type painting. One of the problems to be solved is a problem of scratch countermeasures.

For improving the scratch resistance, there is a technique of mixing and using a silicate material having a relatively high hardness from the viewpoint of increasing the hardness of the coating film. In Patent Document 1, a water-dispersible vinyl copolymer is produced in the presence of a tetrafunctional silicate compound to obtain a resin for coating. It is effective for improvement, but it is not effective for deep scratches, for example, the problem of film peeling due to contact between aluminum sashes, or the problem of film peeling due to rail operation, and weather resistance and paint stability are insufficient. It is. Patent Document 2 is a technique for improving the scratch resistance by reacting colloidal silica and a carboxyl group-containing acrylic resin, but as in Patent Document 1, it is less effective against deep scratches. Patent Document 3 is a technique in which polysiloxane dispersed in a molecular state in an ionic resin is used in combination, and weather resistance and acid rain resistance have some performance, but scratch resistance is insufficient.
Apart from these techniques, a technique using resin particles has been devised. In Patent Document 4, it is a method of using fluororesin particles, which is effective not only for improving the scratch resistance of the coating film surface but also for deep scratches to some extent. However, since fluorine is used for the resin particles, the coating film is slippery, and there is a problem in adhesion with the auxiliary material. Patent Document 5 is a method of using hard resin particles, which is effective for improving the scratch resistance of the coating film surface, but has no effect on deep scratches.
Thus, in the prior art, the problem of scratch resistance is not solved, and there is a demand for improved performance.
JP-A-11-315254 JP 11-172165 A JP-A-11-209694 Japanese Patent Laid-Open No. 2001-329209 JP-A-2001-342425

  In the above-mentioned conventional anionic electrodeposition coating, the coating film and the packing material are used when the aluminum sash is packed with a packing material such as corrugated cardboard or when the packed coating is transported. Although the problem that the surface of the coating film is scratched and the surface of the coating film is scratched to lower the commercial value is solved to some extent, it is not an effective means particularly for deep scratches. The present invention has been made to sufficiently solve such problems.

  As a result of intensive studies to solve the above problems, the inventors of the present invention were excellent in scratch resistance by blending silicone resin particles into anionic electrodeposition paint based on a specific vinyl copolymer. The present invention was completed by successfully establishing an anionic electrodeposition paint.

  That is, the present invention provides (A) an α, β-ethylenically unsaturated carboxylic acid monomer, a hydroxyl group-containing α, β-ethylenically unsaturated monomer, and other α, β-ethylenically unsaturated monomers. A vinyl copolymer having an acid value of 10 to 150 KOHmg / g resin solids (hereinafter the same), a hydroxyl value of 20 to 200 KOHmg / g resin solids (the same applies hereinafter), (B) an amino resin, and (C ) An anionic electrodeposition paint comprising silicone resin particles mainly composed of dimethylpolysiloxane.

  In the present invention, it is particularly effective for preventing deep scratches as well as shallow scratches on the coating surface, and other properties (solvent resistance, chemical resistance, weather resistance, mechanical properties, paint workability, paint stability, etc.) Is the same as conventional paint.

  Next, the electrodeposition paint and the electrodeposition coating method of the present invention will be described in detail.

[(A) Vinyl copolymer]
The α, β-ethylenically unsaturated carboxylic acid monomer in the vinyl copolymer (A) used in the present invention imparts water dispersibility and electrophoretic properties to the vinyl copolymer. Examples include acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid and the like. These 1 type (s) or 2 or more types can be mixed and used.

  The amount of the α, β-ethylenically unsaturated carboxylic acid monomer used is such that the acid value of the vinyl copolymer is preferably 10 to 150, more preferably 20 to 100. If the acid value of the vinyl copolymer is less than 10, sufficient water dispersion stability is difficult to obtain, and if it exceeds 150, the electrophoretic properties and coating film deposition properties deteriorate, and the water resistance and alkali resistance of the coating materials decrease. .

  The hydroxyl group-containing α, β-ethylenically unsaturated monomer reacts with the melamine resin to impart curability when the coating film is baked. Examples include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, and the like. A lactone modified substance is mentioned, It can use 1 type or in mixture of 2 or more types.

  Such a hydroxyl group-containing α, β-ethylenically unsaturated monomer is used in such a range that the hydroxyl value of the vinyl copolymer is preferably 20 to 200, more preferably 40 to 160. When the hydroxyl value is less than 20, sufficient curability is not ensured, and when it exceeds 200, the coating film becomes brittle, water resistance is lowered, and it is difficult to obtain sufficient performance.

  For other α, β-ethylenically unsaturated monomers, alkyl esters of acrylic acid or methacrylic acid, or other vinyl monomers and amide monomers can be used. Specific examples of the compound include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl. Acrylic acid such as methacrylate, t-butyl acrylate, t-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate or the like Methacrylic acid Alkyl monomers, styrene, α-methylstyrene, vinyl toluene, vinyl acetate, acrylonitrile, methacrylonitrile, and other vinyl monomers, acrylamide, methacrylamide, methylol acrylamide, methylol methacrylamide, methoxymethyl acrylamide, n-butoxymethyl acrylamide, Examples thereof include amide monomers such as diacetone acrylamide and diacetone methacrylamide. These may be used alone or in combination of two or more.

  Further, by using an α, β-ethylenically unsaturated monomer having a crosslinkable functional group, it is possible to stably generate an insoluble microgel in the vinyl copolymer and to impart matte performance. Examples include acetoacetoxyethyl acrylate, acetoacetoxyethyl methacrylate, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, β- Examples include methyl-substituted glycidyl acrylate and β-methyl-substituted glycidyl methacrylate. After water-dispersion by a method described later, a microgel is formed in the dispersed particles to reduce gloss. In particular, acetoacetoxyethyl acrylate and acetoacetoxyethyl methacrylate are preferable because the formation of microgel is promoted by using formaldehyde in combination.

  The preferred weight average molecular weight of the vinyl copolymer (as measured by gel permeation chromatography (GPC) in terms of polystyrene) is 10,000 to 100,000, more preferably 20,000 to 70,000. (Hereinafter, all descriptions of the molecular weight of the copolymer and the like represent the molecular weight in terms of polystyrene by GPC). When the weight average molecular weight is 10,000 or less, the coating film durability is not sufficiently obtained. When the weight average molecular weight is 100,000 or more, the water dispersibility is lowered and the handling property of the coating becomes poor.

  The vinyl copolymer as described above is obtained by polymerizing each of the above monomers by a known method such as solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Polymerization is preferred, and the reaction temperature is usually 40 to 170 ° C.

  Reaction solvents include n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol, propyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono It is preferable to use a hydrophilic solvent such as butyl ether. Moreover, as a polymerization initiator, well-known things, such as an organic peroxide, an azo compound, ammonium persulfate, potassium persulfate, can be used.

  In order to disperse the obtained vinyl copolymer in water, at least a part of the carboxyl groups in the vinyl copolymer is neutralized with a basic substance such as an organic amine or an inorganic base. Examples of such basic substances include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, tributylamine and other alkylamines, diethanolamine, diisopropanol Alkanol amines such as amine, triethanolamine, dimethylethanolamine, diethylethanolamine, alkylenediamines such as ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, ammonia, ethyleneimine, pyrrolidine, piperidine, piperazine, morpholine, sodium hydroxide, A potassium hydroxide etc. are mentioned. The neutralization rate with such a basic substance is suitably 30 to 120%, but particularly 50 to 100% is preferable because water dispersibility is good and gloss unevenness does not occur.

[(B) amino resin]
Examples of the (B) amino resin used in the present invention include conventionally known melamine resins, benzoguanamine resins, urea resins, and the like. Among them, preferred is alkoxylation of at least a part of methylol group with a lower alcohol. In the alkyl etherified methylol melamine resin, as the lower alcohol, one or more of methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like can be used. Moreover, even if it is 1 type of melamine resin and 2 or more types of melamine resins are combined, there is no problem.

  Examples of alkyl etherized methylol melamine resins include Cymel 266, 232, 235, 238, 236, 285-100 manufactured by Nippon Cytec Industries, Ltd., Mycoat 506, 508, and Nikalac MX- manufactured by Sanwa Chemical Co., Ltd. 40, MX-45 and the like, but are not limited thereto.

  A preferable range of the amount of the (B) amino resin used in the present invention is 30 to 100 parts by weight with respect to 100 parts by weight of the (A) vinyl copolymer in terms of solid content ratio. If it is less than this range, the mechanical properties, solvent resistance, chemical resistance, etc. will be reduced due to insufficient crosslinking of the coating film, and conversely if it is more, the affinity with the vinyl copolymer will be insufficient, Problems such as poor stability of the aqueous dispersion, unevenness of the dispersed particle diameter, poor washability after electrodeposition, water repellency, uneven gloss of the coating film, and opacification occur.

[(C) Silicone resin particles mainly containing dimethylpolysiloxane]
The (C) dimethylpolysiloxane-based silicone resin particles used in the present invention have a basic structure of a polysiloxane skeleton in which silicon atoms and oxygen atoms are bonded, and if necessary, trifunctional or tetrafunctional silicon-containing Particles having a structure crosslinked or not crosslinked with a compound such as methyltrimethoxysilane or methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, etc., and by combining them, the scratch resistance of the coating film Is greatly improved.
In particular, it is extremely effective in preventing deep scratches such as peeling of the coating film due to contact between the above-described aluminum sashes or peeling of the coating film due to rail operation. As the test method, evaluation was performed by a scratch damage test described later.

Silicone resin particles containing dimethylpolysiloxane as a main component contribute to the elasticity of the coating film, and it is considered that the scratch resistance is improved by the elasticity of the coating film. The average particle diameter is preferably 0.1 μm or more and 30 μm or less, more preferably 0.1 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm from the viewpoint of the smoothness of the coating film. It is as follows. The average particle diameter is a value measured by laser light diffraction.
While ordinary resin particles have a carbon / carbon bond as the basic skeleton, the silicone resin particles of the present invention have a structure in which silicon / oxygen bonds are the basic skeleton and two silicon atom methyl groups are bonded. It is presumed to be caused by For this reason, when the silicone resin particle of this invention is used together, the elasticity modulus of the coating film obtained will be improved significantly and the effect of this invention will be acquired.
The internal structure of the silicone resin particle of the present invention includes a uniform structure or a structure having a so-called core-shell structure in which the structure is different between the outside and the inside of the particle. More preferred is a case having a core-shell structure. For example, if the hydrophilicity of the shell part is increased with respect to the core part, compatibility with the paint can be improved, and scratch resistance can be further improved. .

  Examples of the silicone resin particles mainly composed of dimethylpolysiloxane of the present invention include KMP-597 (average particle size 5 μm), KMP-600 (average particle size 5 μm), KMP-605 (average) manufactured by Shin-Etsu Chemical Co., Ltd. Particle size 2μm), Trefill E-600 (average particle size 2μm), Trefill E-606 (average particle size 2μm), 33Additive (average particle size 2μm) manufactured by Toray Dow Chemical Co., Ltd. Is not to be done.

The preferred range of the amount of the silicone resin particles mainly composed of (C) dimethylpolysiloxane of the present invention is 100 parts by weight of a mixture of (A) vinyl copolymer and (B) amino resin in solid content ratio. The amount is 0.1 to 5 parts by weight. When the amount is less than this range, the scratch resistance is not sufficient. On the other hand, when the amount is too large, the coating becomes unstable and aggregates and precipitates are generated. The more preferable range of (C) component is 0.3-3 weight part.
In addition, additives used in ordinary electrodeposition paints such as curing catalysts, antifoaming agents, leveling agents, and surfactants are also used without any problem as necessary for the preparation of electrodeposition paints. be able to. Furthermore, the technique of the present invention can also be applied to a colored electrodeposition paint using pigments in combination, and a matte electrodeposition paint using a microgel or the like as described above.

[Preparation of electrodeposition paint]
The electrodeposition coating material of the present invention was prepared by stirring and mixing the above-mentioned (A) vinyl copolymer, (B) amino resin, and (C) silicone resin particles mainly composed of dimethylpolysiloxane at 40 to 100 ° C. Thereafter, a general method is to add a curing catalyst and stir and mix deionized water containing a basic substance for neutralization at a temperature of 20 to 80 ° C. to obtain an emulsified dispersion. Further, it is heated as necessary, or diluted with deionized water or deionized water partially containing a hydrophilic solvent, and used for electrodeposition coating.

[Electrodeposition coating method]
The electrodeposition paint obtained by the present invention is diluted with deionized water or deionized water partially containing a hydrophilic solvent, if necessary, and used for matte or glossy type electrodeposition coating. In the case of performing electrodeposition coating, the solid content concentration of the coating bath is suitably 4 to 20% by weight. If it is lower than 4% by weight, it takes a long time to obtain the required coating thickness. If it exceeds 20% by weight, the bath liquid becomes unstable and the amount of paint taken out of the coating system is also a problem. It becomes.

  As for the coating method, electrodeposition is performed using the object to be coated as an anode. The coating voltage is 30 to 350 V, preferably 50 to 300 V, and the energization time is 0.5 to 7 minutes, preferably 1 to 5 minutes. is there. The higher the voltage, the shorter the energization time, and conversely, the lower the voltage, the longer the energization time. The painting voltage may be either a method of applying a set voltage simultaneously with energization or a method of gradually increasing to a set voltage. The electrodeposition-coated object is washed with water if necessary, and then heated at 150 to 200 ° C. for 15 to 60 minutes to obtain a final coating film. The coating thickness is preferably 5 to 30 μm.

  The material of the object to be coated to which the electrodeposition coating method of the present invention is applied is not particularly limited as long as it has conductivity, but is suitable for a material using aluminum or an aluminum alloy. Moreover, the obtained coating film is excellent in appearance such as smoothness and uniformity, and also in performance such as mechanical properties, solvent resistance, chemical resistance, and weather resistance.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In addition, the compounding quantity in a table | surface represents a weight part unless there is special description.

[Production of vinyl copolymer]
Production Examples 1 to 4 (Production of resin liquids A1 to A4)
A reactor having a stirring device, a thermometer, a monomer dropping device, and a reflux cooling device is prepared. In accordance with the formulation shown in Table 1, (1) and (2) were charged into a reactor, raised to reflux temperature with stirring, and (3) to (12) were mixed uniformly in advance and then added dropwise over 3 hours. . The temperature was maintained at 90 ° C. (1.5) is added 1.5 hours after the completion of the dropping, and the reaction is further continued at 90 ° C. for 1.5 hours to obtain transparent and viscous resin liquids A1 to A4 having a resin solid content of 65%. Obtained. Their acid values, hydroxyl values, and weight average molecular weights are also shown in Table 1.

[Production of dispersion resin liquid and electrodeposition paint]
A reactor having a stirrer, a thermometer, and a reflux cooling device was prepared, and (1) to (9) were charged according to the formulations shown in Tables 2 to 3, and stirred and mixed at 60 ° C. for 1 hour. (10) was added thereto, and then (11) was gradually added to obtain a dispersed resin liquid. Regarding dispersion resin liquids B1 and B7, (12) was further added, and the mixture was kept at 50 ° C. for 4 hours to carry out a microgelation reaction. The dispersion resin liquids B2, B5, and B8 remain as they are, and microgels are already generated. The dispersion resin liquids B3 and B9 were incubated at 75 ° C. for 10 hours to carry out a microgelation reaction. Finally, (13) was added to each of B1 to B10 to prepare a dispersion resin liquid having a solid content of 30%.

Cymel 238, Cymel 236, and Cymel 235 in the table are melamine resins manufactured by Nippon Cytec Industries, Ltd.
KMP-597 and KMP-600 are silicone resin particles manufactured by Shin-Etsu Chemical Co., Ltd., and both have an average particle size of 10 μm or less.

[Manufacture of electrodeposition paint]
After adding deionized water to the above dispersion resin liquids B1 to B10 to adjust the solid content to 10%, triethylamine was added to adjust the pH to 8.0 to obtain the respective electrodeposition paints C1 to C10. .

[Electrodeposition coating and coating film performance evaluation]
(Examples 1-6, Comparative Examples 1-4)
The electrodeposition paints obtained above (Examples 1-6 use electrodeposition paints C1-C6, Comparative Examples 1-4 use electrodeposition paints C7-C10) are placed in a vinyl chloride tank, and the cathode is a SUS304 steel plate. Then, the 6063S aluminum alloy plate was alumite-treated (alumite film thickness = 9 μm), further colored electrolytically to black, and then electrodeposited with an aluminum material washed with hot water by a conventional method as an anode (coating material). . The specific conditions for the electrodeposition coating were as follows: the bath temperature was 22 ° C., the distance between the electrodes was 12 cm, and the electrode ratio (+/−) 2/1. After completion, it was washed and subsequently baked at 185 ° C. for 30 minutes. The obtained coating film was evaluated for performance and the results are shown in Tables 4-5.

The evaluation method is as follows.
(1) Gloss value: 60 ° specular reflectance is measured with a gloss meter.
(2) Pencil hardness: Based on JIS K-5600, torn determination.
(3) Adhesiveness: After making 100 grids with a cutter knife on the coating film and attaching cellophane adhesive tape (CT-12S manufactured by Nichiban Co., Ltd.) on it, quickly peel off the cellophane adhesive tape. Observe the state of adhesion. The resulting numbers mean the following:
100/100: No peeling of coating film.
0/100: All peeled off.
(4) Alkali resistance: The coated surface state was observed after immersion in a 1% aqueous sodium hydroxide solution at 20 ° C. for 48 hours.
(5) Acid resistance: The state of the coated surface was observed after immersion in a 5% sulfuric acid aqueous solution at 20 ° C. for 48 hours.
(6) Scratch resistance: A load of 200 g / cm ² was applied to corrugated paper, and after 50 reciprocating frictions with a 5 cm stroke, the degree of scratches on the painted surface was visually evaluated.
○ = Scratches are not visible.
Δ = Scratches are visible but not so white as to be planar.
× = The scar appears as a white surface.
(7) Scratch scratch test: Evaluation was performed using Tribogear TYPE 18 manufactured by Shinto Kagaku Co., Ltd. The measuring method is as follows. Measurement mode is constant load (1kg), indenter is ball indenter 5φmm, stroke distance is 40mm, stroke speed is 10mm / sec. The number of strokes when the indenter reached the aluminum plate was determined.

  By applying the anionic electrodeposition coating material of the present invention, it is possible to provide a coating film that is excellent in coating film appearance and coating film performance and is particularly effective in preventing not only shallow scratches on the coating film surface but also deep scratches. became. Moreover, as a to-be-coated object, it is especially suitable for the coating of an aluminum raw material.

Claims (4)

  (A) Acids obtained by copolymerizing α, β-ethylenically unsaturated carboxylic acid monomers, hydroxyl group-containing α, β-ethylenically unsaturated monomers, and other α, β-ethylenically unsaturated monomers 10 to 150 KOH mg / g resin solid content, hydroxyl value 20 to 200 KOH mg / g resin solid content vinyl copolymer, (B) amino resin and (C) silicone resin particles mainly composed of dimethylpolysiloxane, C) The amount of the silicone resin particles containing dimethylpolysiloxane as a main component is 0.1 to 5 parts by weight with respect to 100 parts by weight as a total of (A) vinyl copolymer and (B) amino resin. Anionic electrodeposition paint.   The anionic electrodeposition paint according to claim 1, wherein the average particle diameter of the silicone resin particles (C) containing dimethylpolysiloxane as a main component is 0.1 µm or more and 30 µm or less.   The anionic electrodeposition paint according to claim 1 or 2, wherein the silicone resin particles (C) having dimethylpolysiloxane as a main component have an average particle size of 0.1 µm or more and 20 µm or less.   The anionic electrodeposition paint according to claim 1, wherein the silicone resin particles (C) having dimethylpolysiloxane as a main component have an average particle size of 0.1 μm or more and 10 μm or less.