JP3192197B2 - UV curable cationic electrodeposition coating composition for plating materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a plating material having water resistance,
The present invention relates to an ultraviolet-curable cationic electrodeposition coating composition that imparts corrosion resistance such as chemical resistance, artificial sweat resistance, and fingerprint resistance and various color variations.

[0002]

2. Description of the Related Art Electrodeposition coating is described in the literature (for example, J. Oil Col,
Chem. Assoc., 63, 482 (1980)), a conductive coating material is dispersed in water, the conductive coating material is immersed in a charged film-forming substance, and a current is applied to cause electrocoagulation, followed by baking. This is a coating method that performs processing.

[0003] The main features of the coating method are that the loss of paint is small, the automatic management of coating is easy and labor costs are reduced, and that various types of objects can be processed simultaneously.
For example, it is possible to form a uniform film on the inner surface and the edge portion of the object to be coated, and it is preferable that the coating has good throwing characteristics. Electrodeposition coating using a water-based paint has also been awarded for environmental pollution and disaster prevention.

[0004] Electrodeposition coating is roughly classified into anion electrodeposition coating and cationic electrodeposition coating. Cathodic electrodeposition coating uses a cathode as the object to be coated, so there is little elution of the underlying metal and chemical conversion film, and the coating resin shows basicity, so that the coating resin itself acts as a corrosion retarder. Because of its high corrosion resistance, it is widely used as a coating method for automobile bodies and industrial materials.

[0005]

However, since the coating film used in the prior art is thermosetting, its curing temperature is as high as 100 ° C. or more, and it cannot be used for heat-sensitive materials such as plastics. There is a problem.

In order to solve this problem, there is a method of curing by ultraviolet irradiation using an ultraviolet-curable paint, which comprises an ultraviolet-curable oligomer, a monomer, a photopolymerization initiator, a sensitizer, and the like. It is called high solid, solventless type. Since the other composition is diluted with a monomer instead of an organic solvent, there is a problem of harmful effects on the human body due to scattering of the monomer during coating. In addition, although a coating film obtained from this type of coating material has high hardness, there is a problem that it is brittle and has poor adhesion to a substrate. In particular, this is a problem on a smooth substrate such as a plating film.

[0007] The object of the present invention is not only general metals,
An electrodeposition coating composition that can be applied to plating products made of plastic or die-cast material, and has excellent adhesion, flexibility, and excellent corrosion resistance, as well as transparency, gloss, and various color variations. To provide.

[0008]

According to the present invention, there is provided a polyfunctional acrylate having three or more acryloyl groups in a molecule.
0 to less than 70 parts by weight, containing a tertiary amino group and a cationic electrodeposition resin having an average molecular weight of 2,000 to 30,000 as 30 to 90 parts by weight as an active ingredient. An ultraviolet curable cationic electrodeposition coating composition for plating materials, characterized by the following:

Further, the present invention provides the above-mentioned cationic electrodeposition resin, wherein the following (a) is contained in an amount of 1 to 20 parts by weight, and the following (b-1), (b-2) or (b-3): It is a copolymer of one or two or more mixtures with less than 99 parts by weight and 80 parts by weight or more, and has an average molecular weight of 3,000 to 3
000, characterized by being a resin having a tertiary amino group in the side chain of the copolymer.

(A) Tertiary amino group-containing vinyl monomer (b-1) α, β-ethylenically unsaturated monocarboxylic acid hydroxy ester (b-2) α, β-ethylenically unsaturated monocarboxylic acid alkyl ester (b -3) α, β-ethylenically unsaturated compound Also, in the present invention, the cationic electrodepositable resin is contained in a polymer.

[0011]

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Wherein R is an average molecular weight of 2,000 to 10, including a tertiary amino group represented by an alkyl group having 4 or less carbon atoms.
000 polyurethane.

In the present invention, the electrodeposition coating composition may contain, if necessary, a paint or a pigment or a mixture thereof.
It is characterized by containing not more than parts by weight.

[0014]

According to the present invention, there are provided 10 to 70% by weight of an acrylate having three or more acryloyl groups which cause a radical polymerization reaction by ultraviolet rays, and 90 to 30% by weight of a cationic electrodeposition resin containing a tertiary amino group. Active ingredients. When a resin having a cationic electrodeposition property is electrodeposited on an object to be coated, the acrylate co-progresses to form a coating film, and the acrylate is radically polymerized and cured by ultraviolet rays. At this time, since there are three or more acryloyl groups in one molecule,
The coating film formed by the polymerization reaction has a three-dimensional network structure, and a coating film having practical strength can be obtained in a short time. As a method for curing these coatings, the use of ultraviolet rays can be cured without raising the temperature of the object to be coated, so that it can be applied to plastic plating products made of ABS resin or the like. There is no possibility that blistering or the like will occur due to the high-temperature baking treatment even for the plated product that has been made. Further, the curing time can be much shorter than that of a general electrodeposition paint requiring high temperature baking treatment, so that the working efficiency can be improved. If the amount of the polyfunctional acrylate having three or more acryloyl groups is less than 10% by weight, it will be insufficient to cure by radical polymerization. In addition, since the cationic electrodeposition resin contains a tertiary amino group, the adhesion to the metal as the plating material increases. When the amount of the cationic electrodeposition resin is less than 30% by weight, the electrodeposition becomes insufficient.

Examples of the polyfunctional acrylate having three or more acryloyl groups include trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol pentaacrylate. Preferably, a resin having good compatibility with the resin having cationic electrodeposition property and capable of obtaining more excellent coating film performance.
Polyester acrylates, urethane acrylates, epoxy acrylates, etc., modified to have more than one functionality are preferred.

The resin having cationic electrodeposition properties is a mixture of 1 to 20 parts by weight of the following (a) and one or more of (b-1), (b-2) or (b-3) 80 ~
A copolymer with 99 parts by weight, the average molecular weight of which is 3,0
It is essential to have a tertiary amino group in the side chain of the copolymer.

(A) Tertiary amino group-containing vinyl monomers such as dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, vinylpyridine, etc. (b-1) α , Β-ethylenically unsaturated monocarboxylic acid hydroxyesters such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate,
(B-2) α, β-ethylenically unsaturated monocarboxylic acid alkyl ester such as methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate,
(B-3) α, β-ethylenically unsaturated compounds such as styrene, methylstyrene, and the like. (B-3) Boronyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, phenoxyethyl (meth) acrylate A tertiary amino group-containing vinyl monomer such as vinylcarbazole (a) is an essential component for imparting cationic electrodeposition property, and this monomer imparts adhesion between the coating film and the underlying plating film. The polymerization ratio is 1 to 20 parts by weight, preferably 3 to 1 part.
0 parts by weight. If the polymerization ratio is too small, it does not disperse in water, has low electrodeposition properties, shows abnormal electrodeposition, and cannot form a uniform coating film. If the amount is too large, the conductivity of the paint increases, which also causes abnormal electrodeposition.

The α, β-ethylenically unsaturated monocarboxylic acid hydroxyester (b-1) copolymerized with the tertiary amino group-containing vinyl monomer has an auxiliary component for dispersing in water and adhesion to the underlying plating film. Used for the purpose of giving The compounding amount can be selected in a wide range, but is preferably 5 to 5.
20 parts by weight. If the amount is too large, the water absorption of the coating film is undesirably increased.

The α, β-ethylenically unsaturated monocarboxylic acid alkyl ester (b-2) is used for the purpose of imparting flexibility and flowability of the coating film, and the compounding amount may be wide as required. Can be selected with.

The α, β-ethylenically unsaturated compound (b-3) is used, if necessary, as an aid for improving physical properties such as water resistance and chemical resistance of the coating film and as a regulator of Tg of the coating film. If the amount is too large, 30 to increase the brittleness of the coating film.
Parts by weight are the limit.

As the copolymerization method, a known radical polymerization method is applied. That is, it can be obtained by solution polymerization using an appropriate solvent such as methanol, ethanol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, butyl cellosolve acetate, toluene, xylene and the like.

Examples of the polymerization initiator include 2,2-azobisisobutylnitrile and 2,2-azobis (2,4
-Dimethylvaleronitrile), benzoyl peroxide and the like.

The resulting copolymer neutralizes its basicity,
Provides water dispersibility required for electrodeposition. Examples of the acid required for neutralization include organic acids such as acetic acid, formic acid, propionic acid, and lactic acid, and inorganic acids such as sulfuric acid and phosphoric acid.

As a resin having cationic electrodeposition properties, a copolymer of the above (a) with one or a mixture of two or more of (b-1), (b-2) and (b-3) is used. When used, the tertiary amino groups and hydroxyl groups added to the side chains impart adhesion to the underlying plating film. The flexibility and hardness of the coating film can be adjusted as necessary by selecting an appropriate component from those contained in (b-2) and (b-3) as the copolymer component.

The resin having cationic electrodeposition properties is as follows:

[0026]

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Wherein R is a molecular weight of 2,000 to 10,000 including a tertiary amino group represented by an alkyl group having 4 or less carbon atoms.
It may be zero polyurethane. Generally, polyurethane is synthesized by a reaction between a dihydric alcohol (diol) and a divalent isocyanate (diisocyanate). In order to introduce the tertiary amino group, a tertiary amino acid is added to a part of the dihydric alcohol. It is an essential condition to incorporate a diol.

The tertiary aminodiol of (c-1) is, for example, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N-
Butyldiethanolamine and the like. Other diols of (c-2) are, for example, ethylene glycol, 1,
3-propanediol, 1,4-butanediol, 1,
5-pentanediol, 1,6-hexanediol, p
-Xylene glycol, polycarbonate diol, caprolactone diols and the like. The molar ratio of the tertiary aminodiol and the other diol used in the above is preferably 1: 3. If the tertiary aminodiol component is less than this, electrodeposition coating becomes impossible, and if it is too large, the appearance of the coating film becomes abnormal.

The diisocyanate (c-3), which is another component of the polyurethane synthesis, is, for example, 4,
4-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, meta-xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4-methylenebis (cyclohexyl isocyanate), trimethylhexamethylene diisocyanate, 1,3- (isocyanatomethyl) cyclohexane, etc. There is.

The above-mentioned diols and diisocyanate are subjected to addition polymerization by a conventional method in a solvent having no active hydrogen, such as benzene, toluene, xylene, acetone, methyl ethyl ketone, methyl acetate, and ethyl acetate.

The resulting polymer neutralizes its basicity,
Provides water dispersibility required for electrodeposition. Acids required for neutralization include organic acids such as acetic acid, formic acid, propionic acid and lactic acid,
Alternatively, inorganic acids such as sulfuric acid and phosphoric acid can be used.

When the polyurethane having a tertiary amino group is used as the resin having a cationic electrodeposition property, a coating film excellent in adhesiveness, water resistance and particularly flexibility can be obtained.

Each of the compositions described above is prepared into an electrodeposition paint by the following method (1) or (2).

(1) A polyfunctional acrylate is prepared by neutralizing a tertiary amino group-containing vinyl monomer with a hydroxy ester of an α, β-ethylenically unsaturated monocarboxylic acid or an α, β-ethylenically unsaturated monocarboxylic acid. Is mixed with one or more copolymers of the alkyl esters of α, β-ethylenically unsaturated compounds, and diluted with ion-exchanged water to a resin content of 8 to 15%.

(2) A polyfunctional acrylate is mixed with the neutralized polyurethane containing a tertiary amino group, and diluted with ion-exchanged water to a resin content of 8 to 15%.

If necessary, a dye or pigment may be added to the UV-curable cationic electrodeposition paint prepared in (1) or (2) to provide a photopolymerization initiator or a color variation. Examples of the photopolymerization initiator used include, for example, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 2-dimethylaminobenzoate, 2,2-diethoxyacetophenone, benzyldimethylketal, benzophenone, and benzoisoethyl. Ether and 2-hydroxy-2-methyl-propiophenone. As the dye to be used, a mordant dye is desirable. Examples of the pigment include organic pigments such as azo-based, phthalocyanine-based, metal complex-based, and quinacridone-based pigments, and inorganic pigments such as titanium dioxide, metal oxides such as iron oxide, and barium sulfate. There are other known carbon blacks.

The mixing ratio of the dye or pigment may be selected according to the desired shade of color, but should not exceed 20% by weight of the whole UV-curable cationic electrodeposition paint. Beyond this, the aforementioned features of the invention are lost.

[0038]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 (1-A) A four-necked flask equipped with a stirrer, a cooler, a thermometer and a dropping funnel in each mouth was charged with 200 g of trimer (isocyanurate) of hexamethylene diisocyanate and 135 g of xylene. Acrylic acid-2 with stirring
A mixed solution obtained by adding 0.46 g of dibutyltin dilaurate having a catalytic action to 116 g of hydroxyethyl and 0.1 g of methquinone as a polymerization agent was dropped at a constant speed from a dropping funnel for 10 minutes, and further kept at 40 ° C. or lower. 90
Stirring was continued for an additional minute to obtain the desired acrylate solution.
The complete reaction of the isocyanate group was confirmed by the disappearance of the absorption at 2270 cm ^{-1 in} the infrared absorption spectrum.

(1-B) 40 g of (a) dimethylaminoethyl methacrylate and (b-1) 2-hydroxyethyl methacrylate 100
g and (b-2) 90 g of 2-ethylhexyl acrylate, 50 g of n-butyl methacrylate and 145 g of methyl methacrylate, and 75 g of (b-3) styrene were added to 300 g of isopropyl alcohol as a solvent, and polymerization was further started. A mixed solution to which 10 g of 2,2-azobisisobutylnitrile was added as an agent was prepared as (1-A)
In the same manner as above, the mixture was charged into a four-necked flask equipped with a stirrer and the like, heated while stirring, and the same amount of the mixed solution having the same composition was further dropped uniformly from the dropping funnel for 90 minutes after the start of the flux, Stirring was further continued at 85 ° C. for 4 hours to obtain a resin solution of these copolymers having cationic electrodeposition properties. GPC confirmed that the average molecular weight of this copolymer was 26,000.

(1-C) 1.9 g of lactic acid was added to 91 g of the copolymer solution obtained in (1-B) for neutralization, and while stirring, 71.4 g of the acrylate solution obtained in (1-A) was added. After adding 1 g of 2-hydroxy-2-methylpropiophenone as a photopolymerization initiator, ion-exchanged water is added with stirring to make the total amount 1 liter, and the ultraviolet curable cationic electrodeposition coating composition of the present invention is obtained. Obtained.

Example 2 2.7 g of lactic acid was added to 127 g of the copolymer solution obtained in (2-C) and (1-B) for neutralization, and while stirring, OPF-, a commercially available trifunctional or more functional acrylate, was added. After adding 30 g of Resin T-1 (trade name, manufactured by Okamura Oil Co., Ltd.) and 1 g of 2-hydroxy-2-methylpropiophenone as a photopolymerization initiator, ion-exchanged water was added with stirring, and the total amount was increased. Was adjusted to 1 liter to obtain an ultraviolet-curable cationic electrodeposition coating composition of the present invention.

Example 3 (3-B) A solution prepared by dissolving 106.7 g of isophorone diisocyanate contained in (c-3) in 75.8 g of xylene was equipped with a stirrer and the like at each port as in (1-A). Into a four-necked flask, and from the dropping funnel with stirring, PLACCEL205 (trade name, contained in commercially available (c-2)).
220.7 g of Daicel Chemical Industries, Ltd.) and (c-
N-methyldiethanolamine 24.4 contained in 1)
g in 75 g of xylene was added dropwise over 30 minutes. The temperature was kept at 40 ° C. or lower, and stirring was further continued for 120 minutes to obtain a polyurethane solution having a tertiary amino group. The complete reaction of the isocyanate group was confirmed by the disappearance of the absorption at 2270 cm ^-1 from the infrared absorption spectrum.

(3-C) 71.4 g of the tertiary amino group-containing polyurethane solution obtained in (3-B) was neutralized by adding 2.2 g of lactic acid, and the resultant mixture was stirred and stirred to obtain a commercially available acrylate, OP.
After adding 150 g of F-Resin T-1 and 1 g of 2-hydroxy-2-methylpropiophenone as a photopolymerization initiator, the ion-exchanged water was added with stirring to make the total amount 1 liter. An electrodeposition coating composition was obtained.

A UV-curable cationic electrodeposition coating composition obtained in each of Examples 1 to 3 was applied to a test piece (5 mm × 5 mm) obtained by applying nickel plating to an ABS resin to a film thickness of 10 μm by a conventionally used method. Electrodeposited with 80
After drying at 10 ° C. for 10 minutes, UV light was applied for 20 cm at a distance of 20 cm using a UV dryer (80 W high-pressure mercury lamp) manufactured by Eye Graphic Co., Ltd.
Irradiated for minutes. Thus, the results of the evaluation test of the completed coating film are shown in Table 1 together with the results of the comparative examples.

[0046]

[Table 1]

The test method is as follows.

Appearance Visual observation. In the comparative example only, some irregularities were observed.

Adhesion Cross-cut test JIS K5651 Hardness Mitsubishi Pencil Uni 1kg load 180 ° bending test A test piece was bent 180 °, a cellophane tape was adhered to the fold, and a peel test was performed.
No mark peeling, × mark complete peeling, △ mark partial peeling CASS72hrs JIS K 8617 or less ○ mark
Normal Acetone Rubs A load of 1 kg is applied to a cloth soaked with acetone, and reciprocated on a test piece, the number of reciprocations until the substrate is exposed. Boiling resistance 5 hrs. Is visually determined 5% NaOH 48 hrs 5% NaOH aqueous solution at 25 ° C.
The appearance was visually determined after immersion in a 5% sulfuric acid aqueous solution at 25 ° C. for 48 hours. The urethane acrylate solution obtained in (1-A) of Example 1 was immersed in the urethane acrylate solution. 1 g of 2-hydroxy-2-methylpropiophenone as a polymerization initiator was added with stirring, and further xylene was added to make a total volume of 1 l to obtain an ultraviolet-curable coating composition. This was dipped twice in the same test piece as used in the examples for 5 seconds to form a coating film, and dried and irradiated under the same conditions as in Examples 1 to 3. This was subjected to the same evaluation test as in the example.

[0050]

As described above, according to the present invention, a tertiary amino group-containing cationic electrodeposition resin is used to form an electrodeposition coating on a substrate to be adhered in a film form so that an acryloyl group can be added to a tertiary amino group.
By irradiating the acrylate having at least one acrylate with ultraviolet rays, the coating film on the object to be coated is polymerized and cured as a three-dimensional network structure. This makes it possible to obtain a coating film that has good adhesion to the plating material, is highly flexible, has excellent anticorrosion properties and transparency, and has a good appearance and is suitable for plating products made of plastic or die cast.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-282468 (JP, A) JP-A-4-153276 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 5/44

Claims (4)

(57) [Claims] 1. A polyfunctional acrylate having three or more acryloyl groups in a molecule, in an amount of 10 to 70 parts by weight, a tertiary amino group, and an average molecular weight of 2,000 to 30,
An ultraviolet curable cationic electrodeposition coating composition for a plating material, comprising as an active ingredient at least 30 parts by weight and less than 90 parts by weight of a cationic electrodeposition resin of 000. 2. The method according to claim 1, wherein the cationic electrodepositable resin comprises:
Is not less than 1 part by weight and less than 20 parts by weight, the following (b-1),
A copolymer of at least 80 parts by weight of less than 99 parts by weight of one or more kinds of (b-2) or (b-3), and having an average molecular weight of 3,000 to 30,000; 2. The ultraviolet curable cationic electrodeposition coating composition for a plating material according to claim 1, which is a resin having a tertiary amino group in a side chain of the copolymer. (A) Tertiary amino group-containing vinyl monomer (b-1) α, β-ethylenically unsaturated monocarboxylic acid hydroxy ester (b-2) α, β-ethylenically unsaturated monocarboxylic acid alkyl ester (b-3) α, β-ethylenically unsaturated compound 3. The method according to claim 1, wherein the cationic electrodepositable resin is contained in a polymer. 2. The ultraviolet curable cationic electrode for a plating material according to claim 1, wherein R is a polyurethane having a tertiary amino group represented by an alkyl group having 4 or less carbon atoms and an average molecular weight of 2,000 to 10,000. Coating composition. 4. The ultraviolet curable cationic electrodeposition for a plating material according to claim 1, wherein said electrodeposition coating composition contains, as necessary, a coating or a pigment or a mixture thereof in an amount of 20 parts by weight or less. Paint composition.