JP2864395B2 - Triboelectric powder coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a triboelectrically-chargeable powder coating composition used for a triboelectrically-charged electrostatic powder coating.

<Prior Art> In recent years, with the diversification of objects to be coated in powder coating, the shape of the object to be coated has become complicated, and it is very difficult to apply powder coating to, for example, a recessed part or the like that has entered. Therefore, a frictional charging type electrostatic powder coating machine capable of easily performing powder coating even in the concave portion or the like has been developed. However, the electrostatic powder coating machine, the material on the inner surface of the coating machine, since the paint is charged using the contact triboelectric charge of the powder paint, the amount of charge differs depending on the composition of the powder paint, not necessarily. At present, it is not always possible to completely coat a concave portion or the like in which an object to be coated has entered. For example, in an epoxy resin and polyester resin-based powder coating composition, the amount of charge is extremely small unless titanium dioxide is contained as a coating component,
It is difficult to paint with an electrostatic coating machine. In addition, even when titanium dioxide is contained, the charge amount is insufficient, and it is currently impossible to apply an epoxy resin or polyester resin-based powder coating composition using an electrostatic coating machine.

<Problems to be Solved by the Invention> An object of the present invention is to provide a triboelectrically-chargeable powder which has excellent triboelectricity and can be easily electrostatically coated by a triboelectric charging method irrespective of the complicated shape of an object to be coated. An object of the present invention is to provide a body coating composition.

<Means for Solving the Problems> According to the present invention, a powder coating material for triboelectric coating comprising 0.1 to 5 parts by weight of a blocked isocyanate compound with respect to 100 parts by weight of a total of an epoxy resin and a polyester resin. A composition is provided.

According to the present invention, the guanamine compound and / or the oxalic acid anilide compound and / or the hindered amine compound are contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the polyester resin. Provided is a powder coating composition for triboelectric charging.

 Hereinafter, the present invention will be described in more detail.

The triboelectric powder coating composition of the present invention (hereinafter abbreviated as composition) is characterized by containing a specific amount of a specific nitrogen-containing compound in an epoxy resin and a polyester resin.

The epoxy resin used in the present invention is a component that reacts with a carboxy group in the polyester resin, and
It is preferred that the resin has an average of two or more epoxy groups. Specifically, for example, triglycidyl isocyanurate, a bisphenol-type epoxy resin, a hydrogenated bisphenol-type epoxy resin, an ester-type epoxy resin and the like can be mentioned, and a commercially available product can also be used. The number average molecular weight and epoxy equivalent of the epoxy resin are preferably a number average molecular weight of 350 to 4000, an epoxy equivalent of 150 to 4000.
g / eq is particularly desirable.

The polyester resin used in the present invention is a resin which is solid at room temperature and has an average of two or more carboxyl groups per molecule, and preferably has a number average molecular weight of 1500 to 8000 and an acid value of 20 to
100 KOH mg / g resin can be used. The polyester resin can be obtained by directly esterifying a carboxylic acid capable of forming a polyester resin mainly composed of terephthalic acid and a polyhydric alcohol mainly composed of ethylene glycol, and using a commercially available product. Can also. Examples of the carboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid,
It is preferably selected from the group consisting of adipic acid, sebacic acid, β-oxypropionic acid, oxalic acid, maleic anhydride, trimellitic anhydride, pyromellitic acid and mixtures thereof, and as the polyhydric alcohol, For example, from ethyl glycol, propanediol, butanediol, pentanediol, 1,6-hexanediol, neopentylglycol, 2,2'-diethylpropanediol, cyclohexanediol, trimethylolpropane, pentaerythritol and mixtures thereof Preferably, it is selected from the group consisting of:

In the present invention, the mixing ratio of the epoxy resin and the polyester resin is preferably in the range of 5 to 70% by weight of the epoxy resin and 95 to 30% by weight of the polyester resin. In consideration of the above, the ratio between the epoxy equivalent and the acid value is preferably set to 0.7 to 1.3. In this case, if the ratio between the epoxy equivalent and the acid value is out of the range, the physical properties of the coating film are unpreferably reduced.

In the present invention, the nitrogen-containing compound is a compound selected from the group consisting of a blocked isocyanate compound, a guanamine compound, an oxalic acid anilide compound, a hindered amine compound, and a mixture thereof,
A compound that imparts triboelectrification to the epoxy resin and polyester resin powder compositions.

The blocked isocyanate compound is a compound in which a free isocyanate group is blocked by reacting a blocking agent with a polyisocyanate compound or an adduct of a polyisocyanate compound and a polyhydric alcohol or isocyanuric acid, and using a commercially available product. Can also. Preferred examples of the polyisocyanate compound include isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, and xylylene diisocyanate. The polyisocyanate compound generates a free isocyanate group by block dissociation, and the free isocyanate group reacts with a carboxy group of the polyester resin in the composition and a hydroxyl group generated by the reaction of the epoxy group of the epoxy resin. It is a compound that also has the function of improving the water resistance of the resulting coating film. Further, as the polyhydric alcohol, for example, trimethylolpropane,
Glycerin, ethylene glycol and the like can be mentioned. Preferred examples of the blocking agent include methanol, ethanol, ε-caprolactam, 2-pyrrolidone, acetoxime, phenol and the like.

On the other hand, the guanamine compound is effective even with guanamine itself, but in consideration of the hygroscopicity and charging stability of the composition, it is preferable to use, for example, a guanamine derivative represented by the following general formula (I).

(Wherein X _{1 to} X ₅ represent a hydrocarbon or a hydrogen atom such as an aryl group, an alkyl group, or an alkenyl group.) Further, in consideration of handleability during the production of a coating material, guanamine represented by the following general formula (II) It is preferable to use a condensate, specifically a condensate with formaldehyde or the like.

(Wherein X is the same as X _{1 to} X _{5 in} the general formula (I).) The oxalic acid anilide-based compound can be represented by the following general formula (IV), (In the formula, R is the same as R ₁ and R _{2 in} the general formula (III).) Specifically, for example, 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5
Preferable examples include t-butyl-2'-ethyloxalic acid bisanilide and the like, and commercially available products can also be used.

The hindered amine compound is a compound containing 2,2,6,6-tetramethylpiperidine in the structure, and preferably, 2,2,6,6-tetramethylpiperidine is condensed with an organic acid. And a commercially available product can also be used. Examples of the organic acid include terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, malonic acid, isocyanuric acid, benzoic acid, propionic acid, β-oxypropionic acid, oxalic acid, and anhydride. Maleic acid, trimellitic anhydride,
It is preferably selected from the group consisting of pyromellitic acid and mixtures thereof. Specific examples of the hindered amine compound include bis (2,2,6,6-tetramethyl-4
-Piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-succinate
2,2,6,6-tetramethylpiperidine polycondensate, 2- (3,5
-Di-t-butyl-4-hydroxybenzyl) -2-n
Bis-butylmalonate (1,2,2,6,6-pentamethyl-4
-Piperidyl), poly [[6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl]
[(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-
Piperidyl) imino]], 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionyloxy] -2,
2,6,6-tetramethylpiperidine, 8-benzyl-7,7,
9,9-Tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine and the like are preferred. Can be mentioned. Further, in addition to the nitrogen-containing compound,
Melamine resins can be used as well.

In the present invention, the content of the nitrogen-containing compound part is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total amount of the epoxy resin and the polyester resin.
It is in the range of parts by weight. In this case, if the amount is less than 0.01 part by weight, sufficient triboelectrification cannot be obtained, and if it exceeds 10 parts by weight, the appearance and physical properties of the coating film deteriorate.

In the present invention, in addition to the epoxy resin, polyester resin and nitrogen-containing compound, if necessary, inorganic pigments such as titanium dioxide, carbon black, iron oxide, and graphite; organic pigments such as cyanine green and cyanine blue: sulfuric acid Additives such as barium, mica, talc, zinc oxide, etc .; metal powders such as aluminum powder, copper powder, nickel powder, etc .; dyes; additives such as pigment dispersants, surface preparation agents, ultraviolet absorbers, catalysts, etc. Can also.

Further, the powder coating composition for triboelectric charging of the present invention can contain a benzotriazole-based compound represented by the following general formula (III).

(In the formula, R ₁ and R _{2 each} represent a hydrocarbon group having 1 to 22 carbon atoms such as an aryl group or an alkyl group or a hydrogen atom, and Y represents a hydrogen atom or a halogen atom.) Specifically, for example, 2- ( 5-
Methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole,
2- (3,5-di-tert-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-tert-butyl-5-
Methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, methyl-3- [3- (2H-benzotriazol-2-yl) -5-t-butyl-4-hydroxyphenyl] propionate, 2- (3, Preferred examples include 5-di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole, and commercially available ones. Articles can also be used.

The composition containing each of the components of the present invention, if the glass transition temperature is less than 40 ° C., the storage stability of the coating is reduced, and if it exceeds 80 ° C., the appearance of the coating film may be reduced, the glass transition temperature Is preferably from 40 to 80 ° C.

In order to prepare the composition of the present invention, for example, each component is uniformly mixed for preferably 0.5 to 5 minutes with a mixer such as “Henschel Mixer” (manufactured by Mitsui Chemicals Co., Ltd.), and then 50 to 150 ° C. Under the temperature conditions described above, for example, it can be obtained by melt-kneading with an extrusion kneader such as “Buscone Kneader PR46” (trade name, manufactured by Bus), cooling, pulverizing with a hammer impact pulverizer or the like, followed by passing.

<Effect of the Invention> Since the composition of the present invention contains a nitrogen-containing compound that imparts triboelectrification, the epoxy resin and the polyester resin-based powder coating composition can be rubbed without impairing the coating film performance. The coating can be performed by a charging type electrostatic coating machine. In addition, it is possible to easily perform electrostatic coating even on a workpiece having a complicated shape. Furthermore,
Since the nitrogen-containing compound of the present invention is achromatic, it can form a coating film of any color as well as clear, and is extremely useful industrially.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
The parts in the examples represent parts by weight.

Example 1 As polyester, trade name "Ester Resin ER860"
90 "(manufactured by Nippon Ester Co., Ltd.) (number average molecular weight 300
0, acid value 36 KOHmg / g), 10 parts (epoxy coat 828) (product name, manufactured by Yuka Shell Epoxy Co., Ltd.) as epoxy resin (number average molecular weight 380, epoxy equivalent 184-194), ε-caprolactam block isophorone diisocyanate Product name "Adduct B-1530" (manufactured by Hls) 2.0 parts,
Product name as a catalyst "Curezol C ₁₇ Z" trade name (Shikoku Chemicals Co., Ltd.) 0.3 parts of a surface modifier "Modaflow" (manufactured by Monsanto) drive render the 0.7 parts (trade name "Henschel mixer" Mitsui Chemical Engineering stock After mixing for about 1 minute with a temperature of 80-120 ° C.
Extrusion kneader (trade name "Busconeder PR46" manufactured by Bus)
The mixture was melt-kneaded using, and after cooling, finely pulverized with a hammer-type impact pulverizer. Then, the mixture was passed through a 180-mesh wire net to obtain a composition. Table 1 shows each component of the composition.

The obtained composition was subjected to a diffuser pressure of 1.0 kgf / cm ² and an injector pressure of 2. using a friction charging type electrostatic powder coating machine (trade name “Tribomatic”) manufactured by Nordson Corporation.
Under the conditions of 0 kgf / cm ² and flowing air of 2.0 kgf / cm ² , coating workability was evaluated using a current value flowing from the coating gun to the ground as a tribomatic load. Table 2 shows the results.

Further, the obtained composition was coated on a 0.8 mm thick steel plate subjected to a zinc phosphate treatment so as to have a film thickness of 50 μm by using the above triboelectric electrostatic powder coating machine, and baked at 190 ° C. for 20 minutes. Performed to obtain a test plate. Each of the obtained test plates was subjected to each test of coating film appearance, impact resistance, flexibility, and corrosion resistance by the methods described below. Table 2 shows the results.

Coating Film Appearance Test A fluorescent lamp was transferred to the coating film, and the transferred fluorescent lamp was checked for distortion, and smoothness and sharpness were visually determined.

Impact Resistance Test According to the impact test of JIS K5400 6.13.3B method, the maximum height at which cracks, cracks, and peeling did not occur in the coating film was measured using a weight of 1/2 inch φ and a load of 500 g.

Flexibility test Measured according to the JIS Z2247 Erichsen test method.

Corrosion resistance test JIS K5400 7.8 After testing the test plate subjected to cross cut in accordance with 7.8 salt spray test with a salt spray tester for 500 hours,
The peeling width of one side of the cut coating film was measured using a cellophane tape (trade name "Sekisui Chemical").

Examples 2 to 15, Comparative Examples 1 to 3 Compositions were prepared in the same manner as in Example 1 except that the components of the composition were changed to the components and amounts shown in Table 1, and each test was performed. Table 2 shows the results.

As is clear from Table 2, the compositions of Examples 1 to 15 containing the nitrogen-containing compound had a tribomatic charge of 1.5 to 1.5.
It was sufficiently high at 3.5 μA, the tribomatic coating workability was good, and the appearance and performance of the coating film were also good. The tribomatic charge of Comparative Examples 1 to 3 containing no nitrogen-containing compound was 0.3 to 0.8 μA, the coating workability was poor, and coating was not possible with tribomatic.

Continuation of the front page (56) References JP-A-53-36528 (JP, A) JP-A-60-35019 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09D 5 / 03,5 / 46

Claims (2)

(57) [Claims] A powder coating composition for triboelectric coating comprising 0.1 to 5 parts by weight of a blocked isocyanate compound based on 100 parts by weight of a total of an epoxy resin and a polyester resin. 2. A triboelectric charge comprising 0.01 to 10 parts by weight of a guanamine compound and / or an oxalic acid anilide compound and / or a hindered amine compound with respect to 100 parts by weight of the total amount of the epoxy resin and the polyester resin. Powder coating composition for painting.