JPH05263026A - Ultraviolet-curable cationic electrodeposition coating composition suitable for plated material - Google Patents

Abstract

PURPOSE:To obtain an electrodeposition coating composition which is applicable to not only ordinary metals but also plated plastic or die-cast-metal articles, is rich in adhesion and flexibility, and imparts excellent anticorrosion by incorporating a polyfunctional acrylate and a specific resin capable of undergoing cationic electrodeposition as the active ingredients CONSTITUTION:This composition contains, as the active ingredients, 10-70, excluding 70, pts.wt. polyfunctional acrylate having three or more acryloyl groups per molecule and 30-90, excluding 90, pts.wt. resin which is capable of being cationically electrodeposited and has an average mol.wt. of 2,000-30,000. The resin is a copolymer of 1-20, excluding 20, pts.wt. vinyl monomer having a tertiary amino group and 80-99, excluding 99, pts.wt. at least one member selected from among hydroxyesters of alpha,beta-unsaturated ethylenic monocarboxylic acids, alkyl esters of alpha,beta-unsaturated ethylenic monocarboxylic acids, and alpha,beta-unsaturated ethylenic compounds.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a plating material having water resistance,
The present invention relates to a UV-curable cationic electrodeposition coating composition which imparts corrosion resistance such as chemical resistance, artificial sweat resistance and fingerprint resistance, and various color variations.

[0002]

2. Description of the Related Art Electro-deposition coating is described in the literature (for example, J. Oil Col,
Chem. Assoc., 63, 482 (1980)), a conductive coating material is immersed in a film-forming substance which is dispersed in water and imparts an electric charge, and is electrically energized to cause electric coagulation, followed by baking. It is a coating method for processing.

The main characteristics of the coating method are that there is little loss of paint, that automatic control of coating is easy and labor costs are reduced, and that various types of objects can be treated simultaneously.
It is possible to form a film evenly on the inner surface and the edge of the article to be coated, and to have a good coating property of the coating material. Also, from the viewpoint of environmental pollution and disaster prevention, electro-deposition coating using water-based paint has been awarded.

Electrodeposition coating is roughly classified into anion electrodeposition coating and cation electrodeposition coating. Cathodic electrodeposition coating uses the 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. It is widely used as a coating method for automobile bodies and industrial materials because of its high corrosion resistance.

[0005]

However, since the coating film used in the above-mentioned prior art is thermosetting, the curing temperature is as high as 100 ° C. or higher, and it cannot be used for a material such as a plastic which is weak against heat. There is a problem.

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

The object of the present invention is not only for general metals,
An electrodeposition coating composition that can be applied to plated products made from plastics and die-casting materials and has excellent adhesion, flexibility, and excellent corrosion resistance, transparency, gloss and various color variations. Is to provide.

[0008]

The present invention provides a polyfunctional acrylate having 3 or more acryloyl groups in a molecule.
A plating material containing 0 part by weight or more and less than 70 parts by weight and 30 parts by weight or more and less than 90 parts by weight of a resin having an average molecular weight of 2,000 to 30,000 having cationic electrodeposition as an active ingredient. A UV-curable cationic electrodeposition coating composition suitable for.

In the present invention, the resin having the cationic electrodeposition property has the following (a) in an amount of 1 part by weight or more and less than 20 parts by weight and the following (b-1), (b-2) or (b-3). ) 1
Copolymer of less than 99 parts by weight and 80 parts by weight or more of one kind or a mixture of two or more kinds, and having an average molecular weight of 3,000.
It is 0 to 30,000, and is 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 In the present invention, the resin having the cationic electrodeposition property is contained in the polymer.

[0011]

[Chemical 2]

However, R is an average molecular weight of 2,000 to 10, containing 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 a coating material or a pigment or a mixture thereof, if necessary.
It is characterized by containing less than or equal to parts by weight.

[0014]

According to the present invention, 10 to 70% by weight of an acrylate having 3 or more acryloyl groups which cause a radical polymerization reaction by ultraviolet rays and a resin 90 having a cationic electrodeposition property.
˜30% by weight as the active ingredient. When a resin having a cationic electrodeposition property is electrodeposited on an object to be coated, the acrylate co-promotes 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 coating films, the use of ultraviolet rays enables the curing treatment without raising the temperature of the object to be coated, so it can be applied to plastic plated products made of ABS resin or the like, and die casting can be used as a material. There is no risk of swelling or the like due to the high temperature baking treatment even for the plated products. Further curing time
The work efficiency can be improved because it can be made much shorter than that of general electrodeposition coating which requires high temperature baking treatment.
When the polyfunctional acrylate having 3 or more acryloyl groups is 10% by weight or less, radical polymerization is insufficient to cure, and when the resin having cationic electrodeposition is 30% by weight or less, electrodeposition becomes insufficient. ..

Examples of the polyfunctional acrylate having three or more acryloyl groups include trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol pentaacrylate. Preferably, it has a good compatibility with a resin having a cationic electrodeposition property and is capable of obtaining a better coating film performance.
Polyester acrylate, urethane acrylate, epoxy acrylate, etc., which are modified to be polyfunctional or higher functional, are preferable.

Examples of the resin having cationic electrodeposition property include 1 to 20 parts by weight of the following (a) and one or a mixture of two or more of (b-1), (b-2) or (b-3). 80 ~
It is a copolymer with 99 parts by weight and its average molecule is 3,0.
It is from 00 to 30,000, and 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 hydroxy ester, for example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate,
Hydroxylbutyl (meth) acrylate etc. (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,
Boronyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. (b-3) α, β-ethylenically unsaturated compounds such as styrene, methylstyrene, Vinylcarbazole, etc. (a) A vinyl monomer containing a tertiary amino group is an essential component for imparting cationic electrodeposition, and this monomer imparts adhesion between the coating film and the undercoat coating film, The polymerization ratio is 1 to 20 parts by weight, preferably 3 to 1
0 parts by weight. If the polymerization ratio is too low, water will not disperse and the electrodeposition will be low, resulting in abnormal electrodeposition, and a uniform coating film cannot be formed. If the amount is too large, the conductivity of the coating material will rise, which also causes abnormal electrodeposition.

The α, β-ethylenically unsaturated monocarboxylic acid hydroxy ester (b-1) copolymerized with the tertiary amino group-containing vinyl monomer is used as an auxiliary component for water dispersion and adhesion to the underlying plating film. It is used for the purpose of giving. The compounding amount can be selected in a wide range, but preferably 5 to
20 parts by weight. If it is too large, the water absorption of the coating film increases, which is not preferable.

The α, β-ethylenically unsaturated monocarboxylic acid alkyl ester (b-2) is used for the purpose of imparting flexibility and flowability to the coating film, and the compounding amount thereof may be in a wide range if necessary. You can select with.

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

As the copolymerization method, a known radical polymerization method is applied. That is, it can be obtained by solution polymerization using a suitable 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,
It provides the water dispersibility necessary for electrodeposition. Examples of the acid required for neutralization include organic acids such as acetic acid, formic acid, propionic acid and lactic acid or inorganic acids such as sulfuric acid and phosphoric acid.

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

The resin having cationic electrodeposition is

[0026]

[Chemical 3]

However, 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 0 polyurethane. Generally, polyurethane is synthesized by the reaction of a divalent alcohol (diol) and a divalent isocyanate (diisocyanate), but in order to introduce the tertiary amino group, a tertiary amino group is partially added to the divalent alcohol. Incorporation of a diol is an essential condition.

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

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

The above-mentioned diols and diisocyanates 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,
It provides the water dispersibility necessary for electrodeposition. As the acid required for neutralization, acetic acid, formic acid, propionic acid, organic acids such as lactic acid,
Alternatively, an inorganic acid such as sulfuric acid or phosphoric acid can be used.

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

Each composition described above can be prepared into an electrodeposition coating composition by the following method (1) or (2).

(1) Polyfunctional acrylate neutralized vinyl monomer containing tertiary amino group and α, β-ethylenically unsaturated monocarboxylic acid hydroxy ester or α, β-ethylenically unsaturated monocarboxylic acid Of the alkyl ester or the α, β-ethylenically unsaturated compound is mixed with one or more copolymers and diluted with ion-exchanged water to obtain a resin content of 8 to 15%.

(2) The polyfunctional acrylate is mixed with the neutralized polyurethane containing the 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 ultraviolet-curable cationic electrodeposition coating composition prepared in (1) or (2) in order to impart a photopolymerization initiator or color variation. Examples of the photopolymerization initiator used include 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 2-dimethylaminobenzoate, 2,2-diethoxyacetophenone, benzyldimethylketal, benzophenone and benzoisoethyl. Ether, 2-hydroxy-2-methyl-propiophenone and the like. A mordant dye is desirable as the dye used. Examples of the pigment include organic pigments such as azo pigments, phthalocyanine pigments, metal complex salt pigments, quinacridone 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 dyes or pigments may be selected according to the shade of the desired color, but it should not exceed 20% by weight of the total UV-curable cationic electrodeposition coating. Above this, the aforementioned features of the invention are lost.

[0038]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

Example 1 (1-A) 200 g of hexamethylene diisocyanate trimer (isocyanurate) and 135 g of xylene were charged in a four-necked flask equipped with a stirrer, a condenser, a thermometer and a dropping funnel in each port. , Acrylic acid-2 with stirring
A mixture of 0.46 g of dibutyltin dilaurate having a catalytic action in 116 g of hydroxyethyl and 0.1 g of methoquinone as a polymerization agent was added dropwise at a constant rate through a dropping funnel for 10 minutes, while maintaining the temperature below 40 ° C. 90
The stirring was continued for a 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) (a) 40 g of dimethylaminoethyl methacrylate and (b-1) 100% of 2-hydroxyethyl methacrylate
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 initiated. As the agent, a mixed solution obtained by adding 10 g of 2,2-azobisisobutylnitrile (1-A)
In the same manner as above, a four-necked flask equipped with a stirrer at each port was charged, the temperature was raised while stirring, and after the flux was started, the same amount of the mixed solution of the same composition was dropped uniformly from the dropping funnel in 90 minutes. Further, the mixture was kept at 85 ° C. for 4 hours to continue stirring to obtain a resin solution having a cationic electrodeposition property which was a copolymer of these. It was confirmed by GPC that the average molecular weight of this copolymer was 26,000.

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

Example 2 2.7 g of lactic acid was added to 127 g of the copolymer solution obtained in (2-C) (1-B) to neutralize it, and OPF- which is a commercially available trifunctional or higher functional acrylate was stirred. Resin T-1 (trade name, manufactured by Okamura Oil Co., Ltd.) (30 g) and 2-hydroxy-2-methylpropiophenone (1 g) as a photopolymerization initiator were added, and ion-exchanged water was added with stirring to make the total amount. To 1 liter to obtain the 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 provided with a stirrer or the like at each port similarly to (1-A). A four-necked flask was charged, and from a dropping funnel with stirring, PLACCEL 205 (trade name, contained in commercially available (c-2)
220.7 g (manufactured by Daicel Chemical Industries, Ltd.) and (c-
1-) N-methyldiethanolamine 24.4
A solution of g and 75 g in xylene was added dropwise over 30 minutes. The temperature was kept at 40 ° C. or lower and stirring was continued for further 120 minutes to obtain a polyurethane solution having a tertiary amino group. In addition, it was confirmed from the infrared absorption spectrum that the absorption at 2270 cm ^-1 disappeared, indicating that the isocyanate group had completely reacted.

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

A test piece (5 mm × 5 mm) made of nickel-plated ABS resin was coated with the UV-curable cationic electrodeposition coating composition obtained in Examples 1 to 3 by a conventional method. Electroplated with 80
After drying at ℃ for 10 minutes, UV ray at a distance of 20 cm for 2 minutes with a UV dryer (80W high pressure mercury lamp) manufactured by Igraphic Co.
Irradiated for minutes. The result of the evaluation test of the completed coating film is shown in Table 1 together with the result of the comparative example.

[0046]

[Table 1]

The test method is as follows.

Appearance By visual inspection. Only the comparative example had some irregularities.

Adhesiveness Cross-cut test JIS K 5651 Hardness Mitsubishi Pencil Uni 1kg load 180 ° bending test Bending the test piece 180 ° and sticking cellophane tape on the crease, peeling test, ○
No mark peeling, × mark complete peeling, △ mark partial peeling CASS72hrs JIS K 8617 or less ○ mark
Normal thing Acetone Rubs A cloth dipped in acetone is loaded with a load of 1 kg, reciprocated on the test piece, and the number of reciprocations until the base material is exposed. Visually determine 5% NaOH 48hrs 5% NaOH aqueous solution at 25 ° C
After visually dipping for 48 hours, the appearance is visually judged. 5% sulfuric acid 48 hrs 5% sulfuric acid aqueous solution is soaked for 48 hours at 25 ° C. After visually observing the appearance, Comparative Example The urethane acrylate solution obtained in (1-A) of Example 1 was exposed to light. 1 g of 2-hydroxy-2-methylpropiophenone as a polymerization initiator was added with stirring, and xylene was further added to adjust the total amount to 1 l to obtain an ultraviolet curable coating composition. A coating film was formed by immersing this in the same test piece used in the example twice for 5 seconds, and drying and irradiation were performed under the same conditions as in Examples 1 to 3. The same evaluation test as in the example was performed on this.

[0050]

As described above, according to the present invention, it is cured by irradiation with ultraviolet rays at room temperature, has good adhesion to a material, is rich in flexibility, and has excellent anticorrosion and transparency.
It is possible to obtain a coating film suitable for plated products made of plastic or die-cast, which has a good appearance.

Claims (4)

[Claims] 1. A polyfunctional acrylate having 3 or more acryloyl groups in the molecule, in an amount of 10 parts by weight or more and less than 70 parts by weight, and having an average molecular weight of 2,000 to 30, which has a cationic electrodeposition property.
000 resin is contained as an active ingredient in an amount of 30 parts by weight or more and less than 90 parts by weight, which is a UV-curable cationic electrodeposition coating composition suitable for a plating material. 2. The resin having a cationic electrodeposition property has the following (a) in an amount of 1 part by weight or more and less than 20 parts by weight and a (b-
1), (b-2) or (b-3), which is a copolymer of one or a mixture of two or more kinds with less than 99 parts by weight and 80 parts by weight or more, and has an average molecular weight of 3,000 to 30, 00
0, which is a resin having a tertiary amino group in the side chain of the copolymer thereof, wherein the ultraviolet curable cationic electrodeposition coating composition suitable for a plating material according to claim 1. (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 compounds 3. The resin having a cationic electrodeposition property in a polymer: However, R is a polyurethane having an average molecular weight of 2,000 to 10,000 containing a tertiary amino group represented by an alkyl group having 4 or less carbon atoms, and an ultraviolet-curable cation suitable for a plating material according to claim 1. Electrodeposition coating composition. 4. The ultraviolet curable cationic electrode suitable for a plating material according to claim 1, wherein the electrodeposition coating composition contains 20 parts by weight or less of a coating material or a pigment or a mixture thereof, if necessary. Coating composition.