JP2001311047A - Electroconductive coating composition and method for electrostatic coating of plastic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive coating composition capable of imparting electrostatic coating suitability to plastic materials, with the surface layer hue uneffected in forming a multilayer coat and having no problem of water resistance of the coating film thereof, and to provide a method for electrostatic coating on plastic materials. SOLUTION: This electroconductive composition is characterized by containing a sulfonium salt compound of formula (1) as an electroconductivity- imparting agent, and the other objective method for electrostatic coating for plastic materials comprises using the compound. [wherein R1 is an (ester- or ester linkage-containing) 8-20C alkyl group; R2 and R3 are each a 1-3C hydroxyalkyl group; X- is an anion resulted from removing a hydrogen atom from an acid compound].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive coating composition for electrostatically coating a plastic member and an electrostatic coating method using the same.

[0002]

2. Description of the Related Art In recent years, automotive parts such as bumpers, fascias, fenders, hoods, trunks,
Many plastic members are used for home electric appliances, precision equipment, office equipment, and the like. As the material of these plastic members, for example, reinforced polyurethane resin, reinforced polypropylene resin, polyethylene resin, F
Examples include RP, ABS resin, vinyl chloride resin, nylon, phenol resin, polystyrene resin, polyacetal resin, and polycarbonate resin. These plastic members are usually coated with a paint for improving aesthetics and durability. As a coating means, electrostatic coating with excellent coating efficiency has come to be frequently used from the viewpoint of resource saving and pollution prevention. However, since plastic members are inferior in electrostatic coating, a method of applying a conductive primer in advance prior to overcoating has been attempted.

For example, JP-A-6-165966 discloses that a conductive primer using a conductive substance such as carbon black or silver is coated and the surface resistance of the coating film is 1 × 10 5
A method for reducing the voltage to ⁸ Ω or less is disclosed. According to this method, although conductivity can be imparted to the plastic member, since the primer is colored, the selection of the hue of the paint that can be overcoated thereon is limited. Further, when a conductivity-imparting agent which does not affect the hue such as a quaternary ammonium salt is added to the coating, there is a problem in the water resistance of a coating film obtained therefrom.
In view of the above, there has been a demand for the development of a conductive primer that does not affect the hue and that enables multi-layer electrostatic coating on plastic members.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plastic member with electrostatic coating suitability,
A conductive coating composition having no influence on the hue of an upper layer when forming a multilayer coating film and having no problem in water resistance of a coating film obtained therefrom, and an electrostatic coating method for a plastic member using the same. It is.

[0005]

Means for Solving the Problems The conductive coating composition for electrostatic coating of the present invention is characterized by containing a sulfonium salt compound represented by the following formula (1) as a conductivity-imparting agent. .

[0006]

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Wherein R ¹ is an alkyl group having 8 to 20 carbon atoms which may contain an ether bond or an ester bond, and R ² and R ³ are hydroxyalkyl having 1 to 3 carbon atoms. The group and X ⁻ represent an anion obtained by removing a hydrogen atom from an acid compound.) The sulfonium salt compound may include a sulfide having two hydroxyalkyl groups having 1 to 3 carbon atoms, an ether bond or an ester bond. It may be obtained by reacting an epoxy compound having an alkyl group having 8 to 20 carbon atoms, an acid compound, and water. Here, the acid compound may be selected from formic acid, acetic acid, propionic acid, sulfonic acid, methanesulfonic acid, ethanesulfonic acid, sulfuric acid, methylsulfuric acid, or phosphoric acid. In addition, the above-mentioned conductivity-imparting agent can be contained in the coating solid content by 1 to 15% by mass. The conductive coating composition for electrostatic coating of the present invention may further contain an epoxy compound, and the acid compound at this time may be a carboxylic acid. On the other hand, the method of electrostatically coating a plastic member according to the present invention involves spraying the conductive coating composition onto the plastic member, forming a coating film, and then electrostatically coating another paint. Another paint may be the conductive paint composition described above.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive coating composition of the present invention contains a sulfonium salt compound represented by the following formula (1) as a conductivity imparting agent.

[0009]

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Wherein R ¹ is an alkyl group having 8 to 20 carbon atoms which may contain an ether bond or an ester bond, and R ² and R ³ are hydroxyalkyl having 1 to 3 carbon atoms. group, X ^-. specific examples of) R ¹ which represents an anion formed by removing a hydrogen atom from an acid compound, octyl group, 2-ethylhexyl group, decyl group, dodecyl group, stearyl group, dodecane group, such as nonylphenyl ether group Can be mentioned. In this specification, an alkylaryl group such as a nonylphenyl ether group is included in the alkyl group. Intended number of carbon atoms of R ¹ is other than 8 to 20, application of electrostatic coatability becomes insufficient. R ² and R ³ may be the same or different. Specific examples of the hydroxyalkyl group having 1 to 3 carbon atoms include a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1,2-dihydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, 3-hydroxypropyl group, 1,2-dihydroxypropyl group, 1,3
-Dihydroxypropyl group, 2,3-dihydroxypropyl group, (2-hydroxymethyl) ethyl group, di (2-
(Hydroxymethyl) methyl group.

On the other hand, the acid compound is not particularly limited, but is preferably formic acid, acetic acid, propionic acid, sulfonic acid, methanesulfonic acid, ethanesulfonic acid, sulfuric acid, methylsulfuric acid or phosphoric acid. Specific examples of the sulfonium salt compound include those having the following structures.

[0012]

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[0013]

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[0014]

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The sulfonium salt compound as the above-mentioned conductivity-imparting agent includes a sulfide having two hydroxyalkyl groups having 1 to 3 carbon atoms and an alkyl group having 8 to 20 carbon atoms which may contain an ether bond or an ester bond. It can be obtained by reacting an epoxy compound, an acid compound, and water.

This reaction can be carried out by a method well known to those skilled in the art, for example, by mixing the above-mentioned compounds at the same equivalent ratio. At this time, it is preferable to heat at less than 100 ° C. to promote the reaction. In addition, a hydrophilic solvent such as methoxypropanol may be added for uniform mixing. Since the reaction does not always proceed completely, it is preferable to end the reaction after a predetermined time, for example, 3 to 12 hours, and to evaporate unreacted raw materials which evaporate under reduced pressure. Thus, the sulfonium salt compound can be obtained. The sulfonium salt compound thus obtained is
Unreacted raw materials that are difficult to volatilize may be included as impurities.

Specific examples of the sulfide having two hydroxyalkyl groups having 1 to 3 carbon atoms include thiodimethanol, thiodiethanol, thiodipropanol, 1-
(2-hydroxyethylthio) -2-propanol, 1
-(2-hydroxyethylthio) -2,3-propanediol and the like. As the epoxy compound having an alkyl group, alkyl ether group or alkyl ester group having 8 to 20 carbon atoms, AOE-X68
(Alkane mixture having 16 to 18 carbon atoms having an epoxy group at the end, manufactured by Daicel Chemical Industries, Ltd.)
0 (tertiary fatty acid monoglycidyl ester, manufactured by Shell). Examples of the acid compound include those described above. The conductive coating composition of the present invention preferably contains the above sulfonium salt compound in a coating solid content at a concentration of 1 to 15% by mass. When the content of the sulfonium salt compound is less than 1%, the effect of improving conductivity is not recognized. On the other hand, if it exceeds 15%, the conductivity is excessively improved, and the electrostatic coating may not be performed.

The conductive coating composition of the present invention can further contain an epoxy compound. By containing an epoxy compound, the thermal decomposability of the sulfonium salt compound can be increased. Here, the epoxy compound is not particularly limited, and may be monofunctional or a resin having two or more epoxy groups. Examples thereof include monoepoxides such as phenyl glycidyl ether and butyl glycidyl ether, diepoxides such as ethylene glycol diglycidyl ether and diethylene glycol diglycidyl ether, and epoxy resins of epibis type or novolak type. Also, alicyclic ones can be used.

The above-mentioned epoxy compound can be added as a third component. For example, when an epoxy group is contained in a coating composition as a component such as an acid / epoxy cured system, this is used as it is. be able to. The amount of the epoxy compound is preferably such that the amount of the epoxy group is 1 equivalent or more based on 1 equivalent of the sulfonium group of the above sulfonium salt compound. If it is less than 1 equivalent, the desired effect may not be obtained. The amount is more preferably 1 to 4 equivalents, but is not limited to the case where the coating composition contains an epoxy group as a component. When the conductive coating composition of the present invention further contains an epoxy compound, the acid compound is preferably a carboxylic acid in consideration of reactivity with an epoxy group. Specific examples of preferred ones include formic acid, acetic acid, propionic acid and the like.

The form of the conductive coating composition of the present invention is not limited as long as it can be sprayed, and may be any of an organic solvent solution type, a non-aqueous dispersion type, an aqueous solution type and an aqueous dispersion type. As the vehicle component contained therein, those having good adhesiveness with a plastic member as an object to be coated are preferable,
Specifically, for example, an epoxy resin, a chlorinated rubber, an acrylic resin, an alkyd resin, a polyurethane resin, an epoxy / phenol resin, a silicone resin, a urethane-modified acrylic resin, an epoxy ester resin, etc. As described above, when the vehicle component has an epoxy group, the thermal decomposability of the sulfonium salt compound can be increased. Further, known curing agents such as melamine and isocyanate can also be included. When the composition contains a curing agent or a vehicle having a curable reactive group, it can be cured by heating or actinic rays. Further, an organic solvent, a coating surface adjusting agent, an additive for a coating such as an anti-drip agent and a surfactant, and a pigment such as a coloring pigment, an extender pigment and a metallic pigment can be added to the above-mentioned coating material, if necessary.

The above-mentioned conductive coating composition can be obtained by mixing the respective components, but can be obtained by adding the above-mentioned sulfonium salt compound and, if necessary, an epoxy compound to those already existing as a coating. Can also. At this time, if necessary, it may be diluted with an organic solvent. The electrostatic coating method for a plastic member of the present invention is characterized in that the above-mentioned conductive coating composition is spray-coated on the plastic member, and another coating is electrostatically coated after a coating film is formed. is there.

The plastic member applicable in the electrostatic coating method of the present invention is not particularly limited. For example, the present invention can be applied to plastic members used for car bumpers, fascias, fenders, hoods and trunks, and plastic members used for home appliances, precision instruments, office supplies, and the like. As the material, for example, polyurethane resin, polypropylene resin,
There are polyethylene resins, polystyrene resins, ABS resins, vinyl chloride resins, nylons, phenolic resins, polystyrene resins, polyacetal resins, polycarbonate resins, etc., alone or in combination, or modified resins, and further reinforced such resins. Can be In addition, the plastic member may have a primer layer obtained by applying a primer paint to be used on the surface.

The method of spray-coating the conductive coating composition is not particularly limited, but it is preferable to mainly use air spray or airless spray. The coating film thickness at this time is preferably in the range of 10 to 50 μm in dry film thickness. If the coating thickness is less than 10 μm, the conductivity required for electrostatic coating cannot be obtained, while if it exceeds 50 μm, the appearance may be adversely affected. In addition, this coating film is used for the next coating without drying.

The coating thus formed has a higher conductivity than the surface of the base material plastic or the plastic on which the primer layer is formed. Can be electropainted. The other paint is not particularly limited. The components contained in this paint may each include those described above for the conductive paint composition. The paint preferably has curability, but since the object to be coated is made of plastic, it is preferable to select a paint that does not cause problems such as deformation due to heating. In addition, when an electrostatic coating is further performed after forming a coating film using this coating material, the coating material may be the above-described conductive coating composition containing the above-described conductivity imparting agent. However, the paint applied first and the paint applied electrostatically are different types. The paint applied earlier serves as a primer,
It is necessary that the paint to be electrostatically coated contains a component that functions as a top coat or an intermediate coat.

Embodiments of the method for electrostatically coating a plastic member of the present invention include the following two embodiments. The first is to form a coating film by spray-coating the above-mentioned conductive coating composition directly on a plastic member as a primer, and then apply another conductive coating composition electrostatically thereon to form a base coating film. Then, a clear coating film is formed thereon using a clear coating material, and these are simultaneously heated to obtain a composite coating film. Secondly, the above conductive coating composition is spray-coated as a base coating on a plastic member having a primer layer formed of a normal primer on the surface to form a coating film, and a clear coating is formed thereon using a clear coating. A composite coating film is obtained by forming films and heating them.

[0026]

EXAMPLES The present invention will be described in detail below, but the present invention is not limited to the following examples. All parts represent parts by mass.

[0027]Synthesis of sulfonium salt compound (1)  AOE-X68 (having an epoxy group at the end)
C16-18 alkane mixture, Daicel Chemistry
1 mol of SHP-100 (1- (2-Hydro)
(Xylethylthio) -2-propanol, Sanyo Chemical Industries, Ltd.
1 mol, 10 mol of deionized water and 1 mol of acetic acid
And stirred at 90 ° C. for 6 hours.
On-water and acetic acid are removed, and a sulfonium represented by the following formula (A)
Thus, a solution containing the potassium salt compound (1) was obtained. Sulfo of this solution
The concentration of the sodium salt compound was 1.0 mmol / g.

[0028]

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[0029]Synthesis of sulfonium salt compound (2)  The acetic acid used for the synthesis of the sulfonium salt compound (1) is meta-
Sulfonium salt compound except that it was changed to sulfonic acid
Performed in the same manner as in the synthesis of (1), and represented by the following formula (B)
A solution containing the sulfonium salt compound (2) was obtained. This solution
Has a sulfonium salt compound concentration of 2.0 mmol / g.
Was.

[0030]

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[0031]Synthesis of sulfonium salt compound (3)  AOE-X used for synthesis of sulfonium salt compound (1)
68 with Kajura E10 (tertiary fatty acid monoglycidide)
Luster, manufactured by Shell Inc.)
The synthesis was carried out in the same manner as in the synthesis of the
A solution containing a sulfonium salt compound (3) represented by (C)
I got The concentration of the sulfonium salt compound in this solution was 1.2.
mmol / g.

[0032]

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[0033]Example 1  6.0 parts of the above-mentioned sulfonium salt compound (1) -containing solution, R
-355 (Acrylic urethane primer, Nippon Beeke
100 parts by Mical Co., solid content 50 mass%), thin for dilution
Mix and stir 50 parts at room temperature as primer
A conductive coating composition (1) was prepared. Also, do the same
The solution containing the sulfonium salt compound (1) 4.0
Part, R-333 (base paint, manufactured by Nippon Bee Chemical Co., Ltd.
(Solid content 33% by mass) 100 parts, thinner 60 parts for dilution
Mixing and stirring at room temperature, conductive paint set as base paint
A product (2) was prepared. In addition, the conductive coating composition (1)
And conductive coating agent in conductive coating composition (2)
The contents in the solid content were both 12% by mass.

The obtained conductive coating composition (1) is applied to a polypropylene plate by air spray so as to have a dry film thickness of 30 μm, and then the conductive coating composition (2) and R-2
98-1 (clear paint, manufactured by Nippon Bee Chemical Co., Ltd.) was electrostatically applied to a dry film thickness of 15 μm and 30 μm, respectively, and baked and dried at 100 ° C. for 35 minutes to obtain a multilayer coating film. The cooled product was used as a test plate, and the conductivity, water resistance and hue of this test plate were evaluated according to the following evaluation methods. The results are shown in Table 1.

[0035]Examples 2-3, Comparative Examples 1-3  Table 1 shows the types of conductivity-imparting agents used for preparing conductive paints.
Modify as described, primer and base, respectively.
Conductive paint compositions (3) to (12) as paints
Was. Using these paints, a test was conducted in the same manner as in Example 1.
The board was prepared and evaluated. Table 1 shows the obtained results.
Posted.

[0036]

[Table 1]

[0037]Evaluation method  (Conductivity) When conductive paint is applied to polypropylene plate
Was evaluated by measuring the specific resistance value of the coating film. ：: Specific resistance value is 10⁸Less than ×: Specific resistance value is 10⁸The (water resistant) test plate was immersed in warm water at 40 ° C. for 10 days.
Then make 100 grids of 1mm square and peel off with adhesive tape
Test performed. The evaluation was based on the number of remaining grids. ：: Number of remaining crosses is 100 △: Number of remaining crosses is 90 to 99 ×: Number of remaining crosses is 0 to 89 (hue) Company color comp
Was measured using a computer SM-7. ：: L value of 65 or more ×: L value of less than 65 As shown in Table 1, the conductive coating composition of the present invention and the static electricity
The coating film obtained by the coating method has excellent conductivity and
The obtained multilayer coating film has excellent water resistance and no problem in appearance.

[0038]Example 4  When manufacturing a conductive coating composition, the epoxy compound YDF
-170 (manufactured by Toto Kasei Co., Ltd.
Sulfonium) with an epoxy group equivalent
Amount that makes the sulfonium equivalent of the salt compound (1) equal
Except for the addition, the conductive coating composition was the same as in Example 1.
(13) was obtained. Implemented this conductive coating composition (13)
A coating film obtained by electrostatic coating in the same manner as in Example 1 was
Bake at 35 ° C, 90 ° C and 100 ° C for 35 minutes each
By drying, a multilayer coating film was obtained. Thus obtained
The multilayer coating film and the conductive coating composition (1) of Example 1
Using the multi-layer coating film obtained under the same conditions,
Sex evaluation was performed. The results are shown in Table 2.

[0039]

[Table 2]

As shown in Table 2, it was confirmed that the addition of the epoxy compound improved the water resistance when baked at a low temperature.

[0041]

Industrial Applicability The conductive coating composition of the present invention can impart suitability for electrostatic coating to plastic members, does not affect the hue of the upper layer when forming a multilayer coating film, and has a water resistant property of the coating film obtained therefrom. Excellent in nature. Further, by further containing an epoxy compound, the water resistance of the coating film at the time of low-temperature baking can be improved. It is considered that the sulfonium compound used as a conductivity imparting agent in the present invention loses hydrophilicity by being converted to sulfide by heating during baking, and as a result, excellent water resistance of the coating film is obtained. Can be In addition, when an epoxy compound is contained, the counter anion of the sulfonium salt compound opens the epoxy group to form a strongly basic anion, thereby reducing the activation energy of thermal decomposition and decomposing. Is considered to be promoted. By using the conductive coating composition of the present invention, a coating material that can be used for the overcoat is not limited, and a plastic member having various colors can be provided. In addition, since baking at a low temperature has become possible, the conductive coating composition of the present invention can be applied to various substrates having insufficient heat resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 7/12 C09D 7/12 H01B 1/12 H01B 1/12 Z 1/20 1/20 Z 13/00 503 13/00 503C (72) Inventor Tetsu Urano 19-17 Ikedanakacho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Keizo Ishii 19-17 Ikedananakacho, Neyagawa-shi, Osaka Nippon Paint Co., Ltd. F term (reference) 4D075 AA09 AE03 CA22 DB31 DC11 DC15 DC18 DC38 EA41 EB33 EB56 4J038 DB001 EA011 JC17 NA20 PA03 PA06 PC08 5G301 DA28 DA53 DA55 DA57 DA59 DD02

Claims (8)

[Claims] 1. A conductive coating composition comprising a sulfonium salt compound represented by the following formula (1) as a conductivity-imparting agent. Embedded image (Wherein, R ¹ represents an alkyl group having 8 to 20 carbon atoms which may contain an ether bond or an ester bond, R ² and R ³ represent a hydroxyalkyl group having 1 to 3 carbon atoms, X ^- represents an anion obtained by removing a hydrogen atom from an acid compound). 2. The method according to claim 1, wherein the sulfonium salt compound has 1 carbon atom.
A sulfide having two to three hydroxyalkyl groups,
The conductive coating composition according to claim 1, which is obtained by reacting an epoxy compound having an alkyl group having 8 to 20 carbon atoms which may have an ether bond or an ester bond, an acid compound, and water with each other. . 3. The method according to claim 1, wherein the acid compound is selected from formic acid, acetic acid, propionic acid, sulfonic acid, methanesulfonic acid, ethanesulfonic acid, sulfuric acid, methylsulfuric acid, or phosphoric acid. The conductive coating composition as described in the above. 4. The conductive coating composition according to claim 1, wherein the solid content of the coating material is 1 to 15% by mass. 5. The conductive coating composition according to claim 1, further comprising an epoxy compound. 6. The conductive coating composition according to claim 5, wherein the acid compound is a carboxylic acid. 7. A method for electrostatically coating a plastic member, wherein the conductive coating composition according to any one of claims 1 to 6 is spray-coated on the plastic member to form a coating film. Electrostatically coating a plastic member. 8. The method for electrostatically coating a plastic member according to claim 7, wherein said another coating is the conductive coating composition according to any one of claims 1 to 6.