JPH1170360A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method for a film providing the uniform hue and satisfying both of glossiness and film strength. SOLUTION: A coloring method for forming a film of uniform hue by mixing two kinds or more of powdery coating materials having different hue comprises a coating process for coating two kinds or more of powder coating materials, a heat melting process for heat melting the applied powdery coating materials and a curing reaction process for curing a hot melted material by heat. It is preferable that the melting process is carried out for the period of time sufficient for heat melting the powdery coating material at the temperature lower than the coating start temperature for the powdery coating material and that the curing reaction process is carried out at the temperature of 70-130% of the curing reaction heating peak temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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.

[0002]

2. Description of the Related Art Conventionally, powder coatings are prepared by adding pigments of several colors to a resin, a curing agent, an additive, etc. in order to obtain a desired hue, mixing, melt-kneading, then cooling, pulverizing, and classifying. By doing so, it has been manufactured. 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.

On the other hand, in order to simplify the process of toning a powder coating, a powder coating in which several kinds of colored powders are mixed has been proposed.

[0004] However, when two or more kinds of powder paints having different hues are uniformly mixed and used as a powder paint,
When a powder coating having a particle size of more than 20 μm is used, particles of the powder coating of each color can generally be visually identified, so that a coating film having a uniform hue cannot be obtained.

Further, when a coating film is formed using such a powder coating material, it is difficult to simultaneously satisfy the required properties of the coating film and the opposite properties of gloss and coating film strength. There is a disadvantage that there is. In general, to improve the gloss, there are known methods of improving the fluidity of the paint or reducing the molecular weight of the resin used in the powder paint, but the strength of the coating tends to decrease. is there. In order to improve the strength of the coating film, there are known methods of increasing the reactivity of the resin used in the powder coating or increasing the molecular weight, but the gloss tends to decrease.

On the other hand, as disclosed in Japanese Patent Publication No. 4-504431, a method of obtaining a coating film having a desired hue by mixing powders of two or more colors of 20 μm or less has been proposed.
μm or less, and 20 μm
In the following, there are drawbacks such as poor fluidity due to easy aggregation and difficult handling.

Further, a method of improving the fluidity by granulating a powder coating by adding a granulating agent solution or the like has been proposed, but this leads to an increase in cost due to an increase in the number of manufacturing steps.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides a coating film having a uniform hue and satisfying both gloss and coating strength. The purpose is to provide a coating method that can be used.

[0009]

The gist of the present invention is to provide (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 step of applying two or more powder coating materials, and heating and melting the applied powder coating material. A coating method characterized by having a heating reaction step and a curing reaction step of curing the heated melt by heat.
(2) The coating method according to (1), wherein the heating and melting step is performed at a temperature lower than the curing start temperature of the powder coating for a time sufficient to heat and melt the powder coating; The coating method according to (1) or (2), wherein the coating is performed at a temperature of 70 to 130% of the peak temperature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The coating method of the present invention is a coating method for obtaining a coating film having a uniform hue by mixing two or more powder coating materials having different hues. A heating step of heating and melting the applied powder coating, and a curing reaction step of curing the heated melt by heat.

In the present specification, a coating film having a "uniform" hue means that the color of each mixed powder coating cannot be visually discriminated because the hue of the formed coating film is uniform. Means that

The powder coating used in the coating method of the present invention is not particularly limited as long as it is generally used as a powder coating, for example, comprising a resin, a curing agent, an additive, a coloring agent and the like.

As the resin, conventionally known resins can be used without any particular limitation. For example,
Examples include non-reactive resins such as polyethylene, nylon resin and vinyl chloride, and reactive resins such as epoxy resin, polyester resin, and acrylic resin. Of these, polyester resins, epoxy resins and acrylic resins are preferred.

As the curing agent, conventionally known curing agents can be used without any particular limitation. For example, polyisocyanate-based curing agents such as tolylene diisocyanate and xylylene diisocyanate;
Isocyanurate-based curing agents such as triglycidyl isocyanurate (hereinafter referred to as TGIC); the above-mentioned polyisocyanate-based curing agent or its isocyanate group at the molecular end of the prepolymer is a known and commonly used blocking agent such as a lactam compound or an oxime compound. Blocked blocked isocyanate-based curing agent; epoxy-based curing agent such as bisphenol A-type diglycidyl ether; alkoxysilane-based curing agent such as methoxysilane oligomer and ethoxysilane oligomer; polyaziridine-based curing such as adipic dihydrazide and succinic dihydrazide 1,4-bis (2-oxazolinyl-2) -benzene, 1,2,4-
Oxazoline-based curing agents such as tris (2-oxazolinyl-2) -benzene and the like can be mentioned. The amount of these curing agents depends on the amount of the functional groups present in the resin, but is preferably in the range of 0.8 to 1.2 in terms of the equivalent ratio of the functional groups.

As the above-mentioned additives, conventionally known additives used in coating compositions can be used without any particular limitation. Examples thereof include a spreading agent such as an acrylate polymer, a crosslinking accelerator such as various catalysts and organic tin compounds, and a pinhole inhibitor such as benzoin.
Each of these additives is preferably used in an amount of about 0.1 to 5 parts by weight based on 100 parts by weight of the resin.

As the colorant, a conventionally known colorant can be used without any particular limitation, and is appropriately selected according to the color tone of the powder coating. For example, titanium oxide, carmine 6B, carbon black, copper phthalocyanine, acetoacetic acid arylamide-based monoazo yellow pigment, disazo yellow, pigment red and the like can be mentioned. The amount used is preferably about 5 to 60 parts by weight based on 100 parts by weight of the resin.

The powder coating used in the present invention is, for example,
The resin, curing agent, additive, colorant, etc. are melt-kneaded by an extruder or the like, and after cooling, physical pulverization is performed using a pulverizer such as a hammer mill or a jet impact mill. -It can be adjusted by classifying using a classifier such as a classifier.

As the powder coating, a powder having an average particle diameter of 1 to 50 μm, preferably 5 to 30 μm can be used and is suitable. Further, from the viewpoint of handling properties, 10 to 20 μm is more preferable. Average particle size of 50
When the average particle diameter is 1 μm or more, the thickness of the obtained coating film can be appropriately reduced.
Agglomeration of the powder coating can be prevented and uniform mixing can be achieved. The powder coating of the present invention has a thickness of 10 μm such as 10 to 20 μm.
A uniform coating film can be easily obtained even in the case of applying a mixture having a particle size slightly larger than m.

Further, the powder coating has silica,
A fluidity modifier such as alumina, titania, or zirconia may be added.

The coating method of the present invention using the powder coating is a coating method having a coating step, a heating and melting step, and a curing reaction step.

The coating step is a step of applying two or more kinds of powder coatings. The method for applying the powder coating is not particularly limited, and examples thereof include a coating method using an electrostatic spray, a fluid immersion method, a plastic spraying method, and a provac method. Upon coating, a mixture in which two or more powder coatings are mixed in advance may be used, or each powder coating may be used individually. As a method of previously mixing two or more kinds of powder coatings, any conventionally known method such as a method of dry-mixing each powder coating 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 the desired hue obtained by color mixing.

The heating and melting step is a step of heating and melting the applied powder coating material. In the present invention, a coating film having a uniform hue can be obtained by heating and melting two or more kinds of applied powder coating materials prior to the curing reaction step.

The heating temperature of the powder coating in the heating and melting step is such that the powder coating is heated and melted without being cured, and two or more powder coatings are sufficiently mixed. The temperature is preferably lower than the curing start temperature, preferably 2 ° C. or lower than the curing start temperature, more preferably 5 ° C. or lower than the curing start temperature.

The heating time of the powder coating in the heating and melting step may be a time sufficient for heating and melting the powder coating. The state of heating and melting of the powder coating can be visually determined.

In the curing reaction step, the heat-melted material heated and melted in the heat-melting step is cured by heat,
This is a step of forming a coating film.

From the viewpoint of reaction efficiency, the curing reaction step is desirably at least 70%, preferably at least 80%, of the peak temperature of the heat generated by the curing reaction. From the viewpoint of economy and prevention of decomposition of the contained components, It is desirable that the temperature is 130% or less, and preferably 110% or less, of the exothermic peak temperature of the curing reaction.

In the present invention, the curing reaction exothermic peak temperature means a temperature at which the curing exothermic value measured by a differential scanning calorimeter shows a peak value.

The curing reaction exothermic peak temperature can be determined from the curve of the exothermic peak measured when the temperature is raised at 10 ° C./min using a differential scanning calorimeter.

The time for curing the powder coating is not particularly limited, but is usually preferably about 10 to 40 minutes.

According to the coating method of the present invention having the above-described steps, a coating film having a uniform hue and satisfying both gloss and coating strength can be obtained.

[0031]

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

The acid value of the obtained resin, the average particle size of the powder coating, the softening point, and the peak temperature of the exothermic curing reaction were measured according to the following methods.

[Acid value] It is measured according to a method according to JIS K0070.

[Average particle diameter] Measured using a Coulter Multisizer (manufactured by Coulter KK).

[Softening point] It is measured by a method according to ASTM E28-67.

[Curing reaction exothermic peak temperature] Using a differential scanning calorimeter (DSC210, manufactured by Seiko Denshi Kogyo Co., Ltd.), it is determined from the curve of the exothermic peak measured when the temperature is raised at 10 ° C./min. .

Resin Production Example 1 155 g (2.5 mol) of ethylene glycol, 624 g (6 mol) of neopentyl glycol, 134 g (1 mol) of trimethylolpropane and 1743 of terephthalic acid
g (10.5 mol) was placed in a 3 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a falling condenser, and a nitrogen inlet tube, and heated to 220 ° C. to react.

The degree of polymerization was monitored from the softening point in accordance with ASTM E28-67, and the reaction was terminated when the softening point reached 95 ° C. The acid value of the obtained resin is 52.9K.
OH mg / g.

The resin is referred to as a binder resin A.

Resin Production Example 2 Ethylene glycol 186 g (3 mol), neopentyl glycol 728 g (7 mol), isophthalic acid 1743
g (9 mol) and 1920 g of trimellitic anhydride (1
0 mol) was placed in a 3 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a falling condenser, and a nitrogen inlet tube, and the temperature was raised to 220 ° C. to react.

The degree of polymerization was monitored from the softening point in accordance with ASTM E28-67, and the reaction was terminated when the softening point reached 100 ° C. The acid value of the obtained resin is 52.0
KOH mg / g.

The resin is referred to as a binder resin B.

Production Example 1 of Powder Coating 100 parts by weight of epoxy resin (YDCN-704, manufactured by Toto Kasei Co., Ltd.) 8 parts by weight of copper phthalocyanine (Cyanine Blue KRS, manufactured by Sanyo Dyeing Co., Ltd.) Moda Flow Powder 2000) 1 part by weight After the above composition was mixed well with a super mixer,
The mixture was kneaded using a Busco Kneader (manufactured by Buss Corp.), cooled, and then ground using a PJM mill (manufactured by Nippon Pneumatics Co., Ltd.) to obtain a powder having an average particle diameter of 23 μm. To 100 parts by weight of the powder, 0.3 part of silica (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) was uniformly mixed using a Henschel mixer to obtain a powder coating (1). The softening point of the powder coating (1) was 96 ° C.

Production Example 2 of Powder Coating 100% by weight of polyester resin (binder resin A) Disazo Yellow (Pigment Yellow ECY-210, manufactured by Dainichi Seika Co., Ltd.) 8 parts by weight Flow-off agent (manufactured by Monsanto, Modaflow Powder 2000) 1 part by weight After the above composition was mixed well with a super mixer,
The mixture was kneaded using a Busco Kneader (manufactured by Buss Corp.), cooled, and then ground using a PJM mill (manufactured by Nippon Pneumatics Co., Ltd.) to obtain a powder having an average particle diameter of 23 μm. To 100 parts by weight of the powder, 0.3 part of silica (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) was uniformly mixed using a Henschel mixer to obtain a powder coating (2). The softening point of the powder coating (2) was 93 ° C.

Production Example 3 of Powder Coatings 100 parts by weight of polyester resin (binder resin A) 15 parts by weight of TGIC (Araldite PT-810, manufactured by Ciba Geigy) 8 parts by weight of copper phthalocyanine (Cyanine Blue KRS, manufactured by Sanyo Dyeing Co., Ltd.) Flow agent (manufactured by Monsanto, Modaflow Powder 2000) 1 part by weight Benzoin 0.5 part by weight After the above composition was mixed well with a super mixer,
The mixture was kneaded using a Busco Kneader (manufactured by Buss Corp.), cooled, and then ground using a PJM mill (manufactured by Nippon Pneumatics Co., Ltd.) to obtain a powder having an average particle diameter of 23 μm. To 100 parts by weight of the powder, 0.3 part of silica (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) was uniformly mixed using a Henschel mixer to obtain a powder coating (3). The softening point of the powder coating (3) was 97 ° C.

Production Example 4 of Powder Coating 100 polyester resin (binder resin B) 100 parts by weight TGIC (araldite PT-810, Ciba-Geigy) 15 parts by weight disazo yellow (Digital Seika Co., Ltd., Pigment Yellow ECY-210) 8 Parts by weight Flow-off agent (manufactured by Monsanto Co., Ltd., Modaflow Powder 2000) 1 part by weight Benzoin 0.5 part by weight
The mixture was kneaded using a Busco Kneader (manufactured by Buss Corp.), cooled, and then ground using a PJM mill (manufactured by Nippon Pneumatics Co., Ltd.) to obtain a powder having an average particle diameter of 23 μm. To 100 parts by weight of this powder, 0.3 part of silica (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) was uniformly mixed using a Henschel mixer to obtain a powder coating (4). The softening point of the powder coating (4) was 100 ° C.

Example 1 50 parts by weight of powder coating (1) and 50 parts by weight of powder coating (2) were mixed using a Henschel mixer, and the resulting mixture was applied to a degreased steel plate by electrostatic spraying. did. Thereafter, the coated powder coating was sufficiently heated and melted by being left at 98 ° C. for 10 minutes, and baked at 180 ° C. for 20 minutes to obtain a coating film. The obtained coating film was uniform green. In addition,
The curing start temperature of the applied powder coating material was 100 ° C., and the exothermic peak temperature of the curing reaction was 160 ° C.

The gloss and pencil strength of the obtained coating film were measured according to the following methods. As a result, the gloss is 90,
The pencil strength was H.

Gloss According to a method based on ASTM 3363-74, a gloss meter (manufactured by Minolta Camera Co., Ltd., G
M-60).

[Pencil strength] JIS K5400 8.4
It is measured according to the method according to the above.

Example 2 50 parts by weight of powder coating (3) and 50 parts by weight of powder coating (4) were mixed using a Henschel mixer, and the resulting mixture was applied to a degreased steel plate by electrostatic spraying. did. Thereafter, the coated powder coating was sufficiently heated and melted by standing at 104 ° C. for 20 minutes, and then baked at 180 ° C. for 20 minutes to obtain a coating film. The obtained coating film was uniform green. In addition, the curing start temperature of the applied powder coating material was 108 ° C, and the exothermic peak temperature of the curing reaction was 145 ° C.

The gloss and pencil strength of the obtained coating film were measured in the same manner as in Example 1. As a result, the gloss is 9
0, pencil strength was 2H.

Comparative Example 1 50 parts by weight of powder coating (1) and 50 parts by weight of powder coating (2) were mixed using a Henschel mixer, and the resulting mixture was applied to a degreased steel plate by electrostatic spraying. did. Thereafter, the film was baked at 180 ° C. for 20 minutes to obtain a coating film. The obtained coating film was an uneven coating film in which cyan and yellow particles were partially observed.

The gloss and pencil strength of the obtained coating film were measured in the same manner as in Example 1. As a result, the gloss is 7
0, pencil strength was HB.

Comparative Example 2 50 parts by weight of powder coating (3) and 50 parts by weight of powder coating (4) were mixed using a Henschel mixer, and the obtained mixture was applied to a degreased steel plate by electrostatic spraying. did. Thereafter, the film was baked at 180 ° C. for 20 minutes to obtain a coating film. The obtained coating film was an uneven coating film in which cyan and yellow particles were visually confirmed.

The gloss and pencil strength of the obtained coating film were measured in the same manner as in Example 1. As a result, the gloss is 8
0, pencil strength was 2H.

From the above results, in Examples 1 and 2, the applied powder coating was heated and melted in comparison with Comparative Examples 1 and 2 in which the coating was formed by directly baking the applied powder coating. After baking and curing to form a coating film, a coating film having a uniform hue and excellent in gloss and strength can be obtained.

[0058]

According to the coating method of the present invention, it is possible to obtain a coating film having a uniform hue and satisfying both gloss and coating strength. Therefore, by preparing several kinds of powder coating materials having different color tones, it is no longer necessary to prepare a variety of powder coating materials having many color tones as in the related art.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Katsutoshi Aoki, 1334 Minato, Wakayama City, Kao Corporation Research Laboratory (72) Inventor Masayuki Maruta, 1334 Minato, Wakayama City, Kao Corporation Laboratory

Claims (3)

[Claims] 1. A coating method for obtaining a coating film having a uniform hue by mixing two or more types of powder coating materials having different hues, wherein a coating step of applying two or more types of powder coating materials, A coating method comprising: a heat melting step of heating and melting a coating; and a curing reaction step of hardening the heated melt by heat. 2. The coating method according to claim 1, wherein the heating and melting step is performed at a temperature lower than the curing start temperature of the powder coating for a time sufficient to heat and melt the powder coating. 3. The coating method according to claim 1, wherein the curing reaction step is performed at a temperature of 70 to 130% of the peak temperature of the heat generated by the curing reaction.