JP2001062385A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method, which can form a coating film having more uniform hue by using two or more kinds of powdery coating materials having different hues and excellent in fluidity, powdery coating materials used for this method, and a production method of a coating film using this method. SOLUTION: This coating method, which provides a coating film of more uniform hue by mixing the colors of two or more kinds of powdery coating materials having different hues, comprises a coating method used by combining one or more kinds of the powdery coating material to be used with a powdery coating material comprising hydrophilic inorganic fine particles having a volume mean particle diameter of 100 nm or less, powdery coating materials used for this method, comprising the hydrophilic inorganic fine particles, and a production method of a coating film using this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for obtaining a coating film having a uniform hue by mixing two or more kinds of powder coating materials having different hues, a powder coating used for the coating method and the coating method. The present invention relates to a method for producing a coating film to be used.

[0002]

2. Description of the Related Art Powder coatings are prepared by adding pigments of several colors to give a desired hue to a resin, a curing agent, additives, etc., mixing, melt-kneading, and then cooling, pulverizing, and classifying. It is manufactured by For this reason, it is inevitable to prepare a paint for each required hue as a powder paint, and an enormous number of products are available. In order to improve this, a method of reducing the particle size of the powder coating (Japanese Patent Application Laid-Open No. Hei 4-504431) and a method of mixing and applying a powder coating that does not thermoset alone are disclosed (Japanese Patent Application Laid-Open No. Hei 10-212435). Is being developed. However, the former method requires a smaller particle size of each powder coating and further granulation, so the process is complicated, and the latter method is an excellent method in that color mixing can be easily performed. However, there are cases where the fluidity is insufficient, and further improvement is desired.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a coating method capable of forming a coating film having a more uniform hue by using two or more kinds of powder coating materials having different hues and excellent fluidity. An object of the present invention is to provide a powder coating used for a coating method and a method for producing a coating film using the coating method.

[0004]

The present invention provides (1) a coating method for obtaining a coating film having a uniform hue by mixing two or more kinds of powder coating materials having different hues. A coating method using a combination of powder coatings containing hydrophilic inorganic fine particles having a volume average particle diameter of 100 nm or less, (2) hydrophilic inorganic fine particles used in the coating method according to (1) above. And (3) a method for producing a coating film using the coating method according to (1).

[0005]

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized by using a powder coating containing hydrophilic inorganic fine particles. The powder coating containing the hydrophilic inorganic fine particles used in the present invention has extremely good fluidity, and the hydrophilic inorganic fine particles have good compatibility with the resin and do not affect the hue. A coating film having a uniform hue can be obtained by using powder coating materials having different hues. In the present specification, a coating film having a “uniform” hue means that the hue of the formed coating film is uniform, so that the color of each mixed powder coating itself is visually observed from a distance of 50 cm. It means that it cannot be distinguished.

The hydrophilic inorganic fine particles in the present invention include hydrophilic silica, titanium oxide, aluminum oxide and the like. Among these, hydrophilic silica and titanium oxide are preferred because of their excellent compatibility with the resin. Hydrophilic silica is more preferred. The hydrophilic inorganic fine particles may be used alone or in combination of two or more.

[0007] The hydrophilic inorganic fine particles in the present invention are those having a property that the surface is easily wetted by water, and the presence or absence of hydrophilicity is determined by whether or not the powder easily settles when the inorganic fine particles are dropped on the water surface. Can be determined by Specifically, it can be determined by a hydrophilicity test method (JISR6127) for artificial abrasives.

The volume average particle diameter of the hydrophilic inorganic fine particles is 100 nm or less, preferably 5 to 50 nm, more preferably 7 to 30 nm, from the viewpoint of affecting the hue.

The content of the hydrophilic inorganic fine particles is preferably from 0.01 to 10 parts by weight, more preferably from 0.1 to 5 parts by weight, based on 100 parts by weight of the resin in the powder coating.

In the present invention, the hydrophilic inorganic fine particles are contained and / or incorporated in the powder coating by preparing the powder coating by melting and kneading the hydrophilic inorganic fine particles together with a resin, a colorant and the like. Or, it may be in a form exposed on the surface, or may be a form in which a powder coating and hydrophilic inorganic fine particles are mixed and adhered to the surface, but the latter is preferable because more excellent fluidity is obtained. Is preferred.

[0011] The powder coating used in the present invention is a powder containing resin, colorant and the like conventionally used for powder coating, as long as at least one of them contains the hydrophilic inorganic fine particles. The body paint can be used without any particular limitation. However, when the resin is a polar group-containing resin, it is preferable because the compatibility with the hydrophilic inorganic fine particles is further improved.

Further, in the present invention, in order to obtain a coating film having a more uniform hue from two or more kinds of powder coating materials having different hues, the coating material is not heat-cured at 250 ° C. or less by itself. It is preferable that the powder coating material has a property of being thermoset at 250 ° C. or less when mixed and applied. Note that “not heat cured” means that an exothermic peak corresponding to heat curing cannot be detected when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC210, manufactured by Seiko Instruments Inc.). Say

Accordingly, as a combination of powder coatings used in the present invention, powder coatings that cause a curing reaction at 250 ° C. or less by melting and mixing resins contained in different powder coatings at the time of heating and melting are used. In the case of using the resin and the resin alone, even if the resin and the resin alone are melt-mixed, the curing reaction does not occur at 250 ° C. or lower, but the powder coating is melt-mixed to cause the curing reaction at 250 ° C. or lower by using the respective curing agents. And an embodiment using a powder coating which is independently thermoset.

(1) An embodiment in which the resins cause a curing reaction In this embodiment, the resins contained in the powder coatings A and B are melted and mixed, so that the functional groups of the resins are cured by a curing reaction. This is an embodiment in which Therefore, as a combination of the powder coating A and the powder coating B used in this embodiment, for example, a resin having a carboxyl group such as a polyester resin, a resin having an amino group such as a polyamide resin,
One or more powder coatings containing at least one resin selected from the group consisting of a resin having a phenolic hydroxyl group such as a novolak resin and an acid-based resin; a resin having an epoxy group such as an epoxy resin; and methacrylic acid. A combination with one or more powder coatings containing at least one resin selected from the group consisting of a resin having a glycidyl group such as a glycidyl-based acrylic resin and a resin having an unsaturated bond, preferably a carboxyl group Or a combination of a powder coating containing a resin having an amino group and a powder coating containing a resin having an epoxy group.

Although it does not thermally cure at 250 ° C. or less by itself,
Resins contained in powder coatings having the property of being thermoset at 250 ° C. or lower by being mixed and applied with other types of powder coatings, various conventionally known resins can be used without limitation. However, the melting temperature of the resin is 250 ° C or less,
The temperature is preferably 90 to 180 ° C., and is preferably adjusted to be equal to or lower than the curing temperature of the mixed powder coating.

The glass transition point of the resin is preferably 40 ° C. or higher in consideration of storage stability and 90 ° C. or lower in consideration of the melting temperature of the powder coating.

The powder coating material of this embodiment does not particularly require a curing agent or a curing catalyst, but may contain a curing agent or a curing catalyst as needed. In this case, a curing agent or a curing catalyst suitable for each resin used in each powder coating is added to the other powder coating to prepare a powder coating that does not cure by itself.

The curing agent may be a known blocked isocyanate-based curing agent, epoxy-based curing agent, alkoxysilane-based curing agent, polyaziridine-based curing agent, oxazoline-based curing agent, imidazole-based curing agent, or the like. What is necessary is just to select suitably according to a functional group.

Powder coatings A and B used in this embodiment
Is preferably 10/90 to 90/10, though it depends on the amount of the functional group present in each resin.

(2) An embodiment in which the resin alone does not cause a curing reaction at 250 ° C. or lower In this embodiment, a curing agent suitable for each resin used in each of the powder coatings C and D is added to the other powder coating. It is a mode of adding. Accordingly, in the powder coatings C and D, preferred specific examples of the combination of the resin and the curing agent include, for example, a powder coating containing an epoxy resin and an oxazoline-based curing agent, a polyester resin having a terminal hydroxyl group other than phenolic and A combination with a powder coating containing an imidazole-based curing agent is exemplified.

The mixing ratio (weight ratio) of the powder coatings C and D is 1
0/90 to 90/10 is preferable, and the compounding amount of the curing agent is
It is preferable to adjust the equivalent of the functional group of the resin to be reacted to 0.8 to 1.2 times.

(3) Embodiment in which each powder coating is thermoset independently This embodiment is an embodiment in which a resin that reacts and thermosets with each other and a powder coating containing a curing agent are combined. Therefore,
Examples of the powder coating used in this embodiment include a combination of a powder coating containing a polyester resin and triglycidyl isocyanurate (TGIC).

The basic colors of the colorants contained in the powder coating material used in the present invention include yellow, magenta, cyan, white, black and the like. The colorants used for each basic color include: For example, disazo yellow and acetoacetic acid arylamide monoazo yellow pigments for yellow, carmine 6B and pigment red for magenta, copper phthalocyanine for cyan, titanium oxide for white, and carbon black for black. The content of the coloring agent is as follows:
0.1 to 60 parts by weight is preferable with respect to 00 parts by weight.

The powder coating material contains, if necessary, additives such as a spreading agent such as an acrylate polymer, various catalysts, a cross-linking accelerator such as an organic tin compound, and an anti-bake agent such as benzoin. May be.

For the powder coating, for example, a resin, a colorant, a curing agent, hydrophilic inorganic fine particles and the like are melt-kneaded by an extruder or the like, and after cooling, using a pulverizer such as a hammer mill or a jet impact mill. Perform physical pulverization, then air classifier, may be prepared by classifying using a classifier such as a Micron classifier, or resin, colorant,
After melt-kneading the curing agent, etc., after cooling, pulverizing and classifying,
It may be prepared by attaching hydrophilic inorganic fine particles to the surface of the obtained powder.

The powder coating thus obtained has a volume average particle diameter of preferably 3 to 80 μm, more preferably 7 to 50 μm. The powder coating having a small particle size of 3 to 10 μm is mixed and agglomerated to obtain a coating of 20 to 50 μm.
May be used as agglomerated particles having a particle size of

The coating method of the present invention is not particularly limited as long as it is a method of applying the powder coating combined according to the present invention, baking and forming a coating film. Examples of the method for applying the powder coating include an application method using an electrostatic spray, an electron gun, or the like, a fluid immersion method, and a plastic spraying method. The temperature, time, and the like at the time of baking cannot be determined unequivocally because they vary depending on the type of resin contained in the powder coating, the curing start temperature of the mixture of the powder coating combined, and the like, but the temperature is 120 to 200 ° C. About 10 to 3 hours
About 0 minutes is preferable. The combined powder coating may be applied to the object to be coated while mixing at the time of coating, but is preferably applied in a premixed state in order to obtain a coating film having a more uniform hue. As a method of mixing two or more kinds of powder coatings, any conventionally known method such as a method of dry mixing with a high-speed stirrer such as a Henschel mixer or a super mixer can be used. The amount of each powder coating used for color mixing is appropriately selected according to a desired hue obtained by color mixing.

Using the coating method of the present invention described above,
A coating film having a uniform hue can be easily produced.

[0029]

EXAMPLE 1 Resin Production Example 1 186 g of ethylene glycol, 728 g of neopentyl glycol, 1494 g of terephthalic acid, 192 g of trimellitic anhydride and 2 g of dibutyltin oxide were placed in a nitrogen atmosphere.
While stirring at 20 ° C., the reaction was performed until the softening point according to ASTM E28-67 reached 90 ° C., to obtain a resin A.
The acid value of Resin A measured by the method of JIS K0070 was 52.4 mgKOH / g.

Production Example 1 of Powder Coating 1 Resin A 100 parts by weight Titanium oxide 10 parts by weight (Taipek CR-50, manufactured by Ishihara Sangyo Co., Ltd .; volume average particle diameter: 250 nm) Disazo Yellow 4 parts by weight (Pigment Yellow ECY-210, large TGIC (Araldite PT-810, Ciba-Geigy) 15 parts by weight Flowing agent (Acronal 4F, BASF) 2 parts by weight

The above-mentioned raw material composition was mixed well with a super mixer, kneaded using a Buscon kneader (manufactured by Bus), cooled, and then ground using a PJM mill (manufactured by Nippon Pneumatic). , Volume average particle size 25μ
m of powder coating (1) was obtained.

Preparation Example 2 of Powder Coating Powder The same procedure as in Preparation Example 1 of powder coating was carried out except that 4 parts by weight of copper phthalocyanine (Cyanine Blue KRS, Sanyo Dye) was used instead of disazo yellow. Paint (2) was obtained.

Production Example 3 of Powder Coating Production Example 1 of powder coating except that TGIC was not used.
In the same manner as in the above, a powder coating (3) was obtained.

Production Example 4 of Powder Coating In place of resin A, epoxy resin (Epicoat 1004A)
F, manufactured by Yuka Shell Co., Ltd.)
A powder coating (4) was obtained in the same manner as in Production Example 2 of the powder coating except that was not used.

Powder Coating Production Example 5 The procedure of Powder Coating Production Example 3 was repeated except that 5 parts by weight of hydrophilic silica (M5, manufactured by Cabot; volume average particle diameter: 12 nm) was added to the raw material composition. Thus, a powder coating (5) was obtained.

Production Example 6 of Powder Coating Same as Production Example 4 of powder coating except that 5 parts by weight of hydrophilic silica (AEROSIL 200, manufactured by Nippon Aerosil Co .; volume average particle diameter: 12 nm) was added to the raw material composition. Thus, a powder coating (6) was obtained.

Example 1 Each of 100 parts by weight of powder coating (1) and powder coating (2) and 0.3 part by weight of hydrophilic silica (M5, manufactured by Cabot Corporation, volume average particle diameter: 12 nm) The powder coating (1a) and the powder coating (2a) were uniformly mixed using a Henschel mixer.

The same weight of powder coating (1a) and powder coating (2
a) was mixed to obtain a powder coating composition. The obtained powder coating composition was applied to a degreased steel plate by electrostatic spraying, and then baked at 180 ° C. for 20 minutes to obtain a coating film.

Example 2 Instead of hydrophilic silica, hydrophilic titanium oxide (P25, manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter: 21 nm) 0.3
A powder coating composition was prepared and a coating film was obtained in the same manner as in Example 1, except for using parts by weight.

Example 3 The procedure of Example 1 was repeated except that the powder coating (1) and the powder coating (2) were replaced with 100 parts by weight of the powder coating (3) and the powder coating (4), respectively. Similarly, a powder coating composition was prepared to obtain a coating film.

Example 4 Instead of hydrophilic silica, hydrophilic titanium oxide (P25, manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter: 21 nm) 0.3
A powder coating composition was prepared and a coating film was obtained in the same manner as in Example 3, except for using parts by weight.

Example 5 The same weight of powder coating (5) and powder coating (6) were mixed.
A powder coating composition was obtained. The obtained powder coating composition was applied to a degreased steel plate by electrostatic spraying.
Baking was performed at 0 ° C. for 20 minutes to obtain a coating film.

Example 6 A powder coating composition was prepared in the same manner as in Example 1 except that the powder coating (1) and the powder coating (2) each having a volume average particle diameter of 3 μm were used. A coating was obtained.

Comparative Example 1 Powder was prepared in the same manner as in Example 1 except that 0.3 parts by weight of hydrophobic silica (R812, manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter: 7 nm) was used instead of hydrophilic silica. A body coating composition was prepared to obtain a coating film.

Comparative Example 2 Powder was prepared in the same manner as in Example 3 except that 0.3 parts by weight of hydrophobic silica (R812, manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter: 7 nm) was used instead of hydrophilic silica. A body coating composition was prepared to obtain a coating film.

Comparative Example 3 A powder coating composition was prepared and a coating film was obtained in the same manner as in Example 1 except that hydrophilic silica was not used.

Comparative Example 4 A powder coating composition was prepared and a coating film was obtained in the same manner as in Example 3 except that hydrophilic silica was not used.

Test Example 1 The angle of repose of the powder coating compositions prepared in Examples 1 to 6 and Comparative Examples 1 to 4 was measured as “POWDER TESTER TYP”.
"EPT-E" (manufactured by Hosokawa Micron Corporation), and the fluidity of each powder coating composition was evaluated according to the following evaluation criteria. Table 1 shows the results.

[Evaluation Criteria] A: Good fluidity when the angle of repose is less than 40 °. Δ: The angle of repose is 40 ° or more and less than 43 °, but there is no problem in painting. ×: Problems occur in painting when the angle of repose is 43 ° or more.

Test Example 2 The uniformity of hue of the coating films obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was evaluated according to the following evaluation criteria. Table 1 shows the results
Shown in

[Evaluation Criteria] When an observer with a visual acuity of 1.0 observes the film at a distance of 30 to 100 cm from the coating film, ◎: even at 30 cm. ：: It looks uneven at 30 cm, but looks uniform at 50 cm. Δ: It looks uneven at 50 cm, but looks uniform at 100 cm. X: It looks uneven even at 100 cm.

[0052]

[Table 1]

From the above results, it can be seen that the powder coatings used in Examples 1 to 6 have good fluidity, and the obtained coating films also have a uniform hue. On the other hand, the powder coatings containing the hydrophobic inorganic fine particles used in Comparative Examples 1 and 2 were excellent in fluidity, but the resulting coating films lacked the uniformity of hue. It can be seen that the powder coating containing no hydrophilic inorganic fine particles used in (1) lacks fluidity and slightly lacks uniformity of hue of the coating film.

[0054]

According to the present invention, it is possible to form a coating film having a more uniform hue by using two or more kinds of powder coating materials having different hues and excellent fluidity. Therefore, by preparing powders of several colors including the primary colors, powders of all colors can be easily obtained, and there is no need to prepare a variety of powder coatings of many colors as in the past. Was.

Continued on the front page (72) Inventor Kenichi Suenaga 1334 Minato, Wakayama-shi, Kao Corporation Research Institute (72) Inventor Hideki Yanagi 1334 Minato, Wakayama-shi, Kao Corporation F-term (reference) 4D075 AA09 BB26Z CB36 DA06 DB02 EA02 EB33 EB35 EB39 EB53 EC02 EC03 EC37 EC53 EC54 4J038 CG142 CH171 CH172 DA031 DA032 DB001 DB002 DB221 DB222 DD001 DD002 DG141 DH001 DH002 GA01 GA03 GA06 GA07 GA09 HA216 HA446 KA02 KA20 MA02 MA14 NA01 NA06 PA02 PA19

Claims (6)

[Claims] 1. A coating method for obtaining a coating film having a uniform hue by mixing two or more kinds of powder coating materials having different hues, wherein at least one of the powder coating materials used has a hydrophilic particle having a volume average particle diameter of 100 nm or less. Coating method using a combination of powder coatings containing conductive inorganic fine particles. 2. The coating method according to claim 1, wherein the hydrophilic inorganic fine particles are hydrophilic silica or titanium oxide. 3. The powder coating composition to be combined with 2
The coating method according to claim 1 or 2, wherein the composition does not thermoset at 50 ° C or lower, but has a property of thermosetting at 250 ° C or lower by being mixed and applied with another type of powder coating. 4. One or more powder coatings containing at least one resin selected from the group consisting of a resin having a carboxyl group, a resin having an amino group, a resin having a phenolic hydroxyl group, and an acid anhydride resin. 4. A combination of at least one powder coating containing at least one resin selected from the group consisting of a resin having an epoxy group, a resin having a glycidyl group and a resin having an unsaturated bond. The painting method described. 5. A powder coating containing hydrophilic inorganic fine particles, which is used in the coating method according to any one of claims 1 to 4. 6. A method for producing a coating film using the coating method according to claim 1.