JP2002275420A - Thermosetting powder coating and method for forming thermosetting powder coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosetting powder coating having excellent smoothness. SOLUTION: The thermosetting powder coating curable at a temperature of >=100 deg.C is characterized in that the lowest viscosity of the powder coating melted by heating up to a curing start temperature is 0.1 Pa.s to 50 Pa.s and in that the time of the thermal flow is >=10 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel powder coating composition and a method for forming a thermosetting powder coating.

[0002]

2. Description of the Related Art In recent years, powder coatings have attracted attention as coatings containing almost no volatile substances, mainly solvents, from the viewpoints of pollution prevention and protection of the global environment. Conventionally, powder coatings have been widely used for outdoor or indoor applications in the field of industrial products such as home appliances, automobiles, vehicles, office supplies, steel furniture, and building materials. As such a powder coating, a thermosetting acrylic resin powder coating, a thermosetting polyester resin powder coating, and a thermosetting epoxy resin powder coating are mainly used.

In recent years, powder coatings having excellent finished appearance have been demanded. However, in order to obtain a coating surface smoothness equivalent to that of a conventional solvent-type coating film having a thickness of about 40 μm, a powder coating of about 60 μm or more is required. A coating film thickness is required, and improvement in smoothness of a thin film of a powder coating material is required. As a method of improving the smoothness of the powder coating, it is conceivable to reduce the particle diameter of the powder coating as much as possible. However, reducing the particle diameter of the powder coating lowers the fluidity of the powder coating. As a result, the workability of powder coating deteriorates, and when the powder paint is electrostatically charged by a spray gun, the chargeability of the powder paint becomes non-uniform, so that the filling property of the coating powder becomes poor. However, there is a problem that the smoothness of the powder coating film is deteriorated due to the reduction, and the smoothness of the powder coating film has not been improved.

[0004]

Means for Solving the Problems The present inventors have intensively studied to solve such problems. As a result, 100
A powder coating which is cured by heating at a temperature of at least 0 ° C., wherein the minimum viscosity of the powder coating melted by heating to the curing start temperature is 0.1 Pa · s to 50 Pa · s, and the flow time is 10 minutes or more. The present inventors have found that a thermosetting powder coating characterized by providing a powder coating film having excellent smoothness has led to the completion of the present invention.

That is, the present invention relates to a powder coating material which is cured by heating at a temperature of 100 ° C. or more, wherein the powder coating material melted by heating to a curing start temperature has a minimum viscosity of 0.1 Pa · s or less.
The present invention relates to a thermosetting powder coating material having a pressure of 50 Pa · s and a heat flow time of 10 minutes or more.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the minimum viscosity of a molten powder coating material is 0.1 Pa · s to 50 Pa · s, preferably 3 Pa · s to 40 Pa · s, more preferably 1 Pa · s.
S to 20 Pa · s. Minimum viscosity is 0.1Pa · s
If it is less than 50 mm, sagging on the vertical surface is likely to occur, while if it exceeds 50 Pa · s, the smoothness will be poor.

[0007] In the present specification, the minimum viscosity and the heat flow time are measured by a powder melt viscosity meter RS100 rheometer (HAA).
It is a value measured using KE Corporation (trade name).

The powder coating of the present invention has an average particle diameter of 5
It is from μm to 30 μm, preferably from 10 μm to 25 μm. When the average particle diameter is less than 5 μm, the coating workability is poor and the electrostatic coating property of the powder coating is poor, so that the finished appearance of the baked coating film is inferior. On the other hand, when it exceeds 30 μm, the smoothness of the baked coating film is inferior. It is not preferable.

The powder coating material of the present invention has a heat softening temperature of 30 ° C.
The temperature is 100 ° C, preferably 40 ° C to 90 ° C. When the heat softening temperature is lower than 30 ° C., the blocking property of the powder coating material is deteriorated, and a lump is easily formed during storage.
When the temperature exceeds ℃, the minimum melt viscosity of the molten powder coating material is increased, and the smoothness of the baked coating film is poor. Further, as the powder coating used in the present invention, a conventionally known thermosetting powder coating can be used. Specifically, a thermosetting powder coating obtained by blending a curing agent with a thermosetting powder base resin that melts and flows by heating itself can be used.

As the thermosetting powder base resin, a resin having a functional group which reacts with a curing agent by heat can be used.
Specifically, for example, an acrylic resin, a polyester resin, an epoxy resin, and a hybrid resin thereof are suitable. Examples of the functional group include a hydroxyl group, a carboxyl group, an epoxy group, and a blocked isocyanate group. As the curing agent, a functional group contained in the curing agent reacts with a functional group in the base resin to form a cured coating film. For example, a base resin containing a hydroxyl group contains an amino group. A curing agent such as an amino resin (hexamethoxymelamine resin, etc.), a blocked isocyanate compound containing a blocked polyisocyanate group (caprolactam blocked diisocyanate, etc.), a polyepoxide containing an epoxy group in a carboxyl group containing base resin (triglycidyl isocyanate, etc.) and Curing agents such as β-hydroxyethylalkylamide, and polycarboxylic acids containing carboxyl groups in the epoxy group-containing base resin (dodecane diacid, eicosane diacid, sebacic acid, adipic acid, trimellitic acid, etc.), and their polycarboxylic acids Anhydrides of those polycarboxylic acids A curing agent such as hydrazide, a polymerization initiator such as imidazoles, a curing agent for a hydroxyl-containing polyol (such as trimethylolpropane) in a blocked isocyanate group-containing base resin, and benzyl-4-hydroxyphenylmethylsulfonium hexafluoroantimonate And a polymerization initiator.

In the present invention, if necessary, a pigment (for example, an organic pigment (for example, a quinacridone-based pigment such as quinacridone,
Azo type such as C.I. Pigment Red, phthalocyanine blue,
Phthalocyanine-based phthalocyanine blue and the like), inorganic pigments (for example, titanium oxide, calcium carbonate, barita,
Clay, talc, silica, etc.), carbon-based pigments (eg, carbon black, graphite, etc.), metallic powders (eg, mica-like iron oxide, aluminum, etc.) and rust-preventive pigments (eg, red iron oxide, strontium chromate, zinc phosphate, etc.) ), Curing catalysts (dibutyltin diacetate, dibutyltin dilaurate, triethylamine,
Or diethanolamine), ultraviolet absorbers (benzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, oxalic anilide-based compounds, etc.), ultraviolet stabilizers (hindered amine-based compounds, etc.), antioxidants (phenol-based compounds, organic An additive such as a sulfur-based compound or a phosphite-based compound), a surface conditioner, or an anti-bake agent can be added.

The powder coating composition of the present invention may be prepared by a conventional method, for example, mixing a base resin, a curing agent and other components as necessary, dry-blending with a mixer, heat-melting and kneading, cooling, and coarsely pulverizing. It can be manufactured by a melt-kneading method involving fine pulverization and filtration, or a freeze-drying method.

The powder coating of the present invention is preferably applied by a corona electrostatic powder spray or a triboelectric powder spray.

The powder coating composition of the present invention may be prepared by coating the above-mentioned powder on the surface of a conductive substrate (for example, metal, surface-treated metal, or a coating product obtained by electrodeposition coating or intermediate coating of these metals). Painted by painting (normally, film thickness 30 μm to 150 μm)
Then, usually, baking is performed at 140 ° C. to 300 ° C. for 1 minute to 60 minutes to form a coating film.

The powder coating of the present invention is obtained by applying the above-mentioned thermosetting powder coating to an object to be coated with the above-mentioned electrostatic powder coating machine, and then applying the minimum viscosity of the coated powder coating. Becomes 0.1 Pa · s to 50 Pa · s, and the heat flow time becomes 1
The thermosetting powder coating can be formed by heating and curing at a temperature of 100 ° C. or more so as to be 0 minutes or more.

[0016]

The thermosetting powder coatings of the prior art had contradictory performances such that when the smoothness was improved, the curability was reduced, while when the curability was improved, the smoothness was reduced.
In contrast, the powder coating of the present invention has a minimum viscosity of 0.1 Pa · s to 50 Pa ·
s, and since the heat flow time is 10 minutes or longer, a coating film having good fluidity and excellent smoothness at the time of film formation of the powder coating is formed, and then the coating film surface is maintained. Since the coating is cured, a coating excellent in both smoothness and curability can be formed.

[0017]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. Hereinafter, "parts" and "%" indicate "parts by weight" and "% by weight", respectively.

Example 1 (Production of Acrylic Powder Coating) Vinyl copolymer (glycidyl methacrylate / n-butyl methacrylate / methyl methacrylate / styrene = 35/15/35/15) Weight ratio, softening temperature 67 ° C., number average molecular weight 3000) 800 parts, dodecane diacid 300
Part, Calcol 8098 (manufactured by Kao Corporation, stearyl alcohol, trade name) 50 parts, Dispalon PL540
(Kusumoto Kasei Co., Ltd., powdered vinyl polymer, trade name) 30 parts and titanium white 300 parts were dry blended at room temperature using a Henschel mixer FM10C manufactured by Mitsui Mining Co., Ltd. The mixture was melt-kneaded with MP-30. After being cooled and coarsely pulverized, finely pulverized with a fine pulverizer (ACM5, manufactured by Hosokawa Micron Corporation), and then classified with an airflow classifier (DSX-2, manufactured by Nippon Pneumatic Industries, Ltd.) to obtain fine particles. The coarse particles were removed to obtain an acrylic powder coating having an average particle size of 20 μm.

The average particle size is a value measured using a particle size distribution analyzer (trade name: Microtrac HRA, manufactured by Nikkiso Co., Ltd.).

The minimum viscosity of the powder coating is 5 Pa ·
s and the heat flow time was 14 minutes.

The minimum viscosity and the heat flow time are values measured using a powder melt viscosity meter RS100 rheometer (trade name, manufactured by HAAKE) or the like. Specifically, 0.5 g of the powder coating was pressed at a pressure of 20 MPa, and the diameter was 2.0
cm pellets were made. Next, the obtained pellets were set on a powder melt viscosity meter RS100 rheometer, heated to 180 ° C. in 10 minutes, and then maintained at 180 ° C. for 20 minutes. And the minimum melt viscosity obtained by continuously measuring the phase difference angle δ and the maintenance time at a phase difference angle of 45 ° or more were obtained as the minimum viscosity of the powder coating and the heat flow time of the powder coating, respectively.

Example 2 (Production of Polyester Resin Powder Coating (Block Polyisocyanate Crosslinking)) As a material, Finedec M8032 (manufactured by Dainippon Ink Co., Ltd., trade name, softening temperature 70 ° C., hydroxyl value 30 m)
gKOH / g) 770 parts, ε-caprolactam blocked isophorone diisocyanate (blocked polyisocyanate crosslinking agent) 230 parts, Calcol 8098 (manufactured by Kao Corporation, stearyl alcohol, trade name) 50 parts,
Except that 30 parts of Disparon PL540 (manufactured by Kusumoto Kasei Co., Ltd., trade name of powdered vinyl polymer, trade name) and 300 parts of titanium white were used, the average particle size was 2 in the same manner as in Example 1.
A 4 μm polyester powder coating was produced. The minimum viscosity of this powder coating is 14 Pa · s, and the heat flow time is 1
5 minutes.

Example 3 (Production of Epoxy Resin Powder Coating) As a material, Epicoat 1004 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name, bisphenol A to epichlorohydrin type epoxy resin, softening temperature 70 ° C., Average molecular weight 1400) 940 parts, adipic dihydrazide 60 parts,
50 parts of Calcol 8098 (manufactured by Kao Corporation, stearyl alcohol, trade name), Dispalon PL540 (produced by Kusumoto Chemicals, powdered vinyl polymer, trade name) 3
Example 1 except that 0 parts and 300 parts of titanium white pigment were used.
An epoxy powder coating having an average particle size of 23 μm was produced in the same manner as in the above. The minimum viscosity of this powder coating is 23 Pa
s and the heat flow time was 10 minutes.

Example 4 (Polyester Resin Powder Coating (Epoxy Resin Curing Agent)) As a material, Finedec M8860 (trade name, manufactured by Dainippon Ink Co., Ltd., acid value 35, softening temperature 60 ° C., number average molecular weight 2000) Powder) 700 parts, epicoat 100
2 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name, epoxy equivalent 550-700, average about 2 epoxy groups) 300
Part, Calcol 8098 (manufactured by Kao Corporation, stearyl alcohol, trade name) 50 parts, Dispalon PL540
(Kusumoto Kasei Co., Ltd., powdered vinyl polymer, trade name) A polyester powder paint having an average particle size of 15 μm was produced in the same manner as in Example 1 except that 30 parts and 400 parts of titanium white were used. did. The minimum viscosity of this powder coating is 41
Pa · s, and the heat flow time was 11 minutes.

Comparative Example 1 (Production of Acrylic Powder Coating) As a material, a vinyl copolymer (glycidyl methacrylate / n-butyl methacrylate / methyl methacrylate) was used.
G / styrene = 35/15/35/15 weight ratio, softening temperature 67 ° C., number average molecular weight 3000), 800 parts, Calcol 8098 dodecane diacid 300 parts, titanium white 200 parts, and An acrylic powder coating having an average particle size of 24 μm was produced in the same manner. The minimum viscosity of this powder coating is 55 Pa · s and the heat flow time is 13
Minutes.

Comparative Example 2 (Production of Acrylic Powder Coating) As a material, a vinyl copolymer (glycidyl methacrylate / n-butyl methacrylate / methyl methacrylate) was used.
G / styrene = 35/15/35/15 weight ratio, softening temperature 67 ° C., number average molecular weight 3000), 800 parts, Calcol 8098 dodecane diacid 300 parts, and titanium white 200 parts, except that An acrylic powder coating having an average particle size of 40 μm was produced in the same manner. The minimum viscosity of this powder coating is 55 Pa · s and the heat flow time is 13
Minutes. Comparative Example 3 (Production of Polyester Resin Powder Coating (Block Polyisocyanate Crosslinking)) As a material, Finedec M8032 (manufactured by Dainippon Ink Co., Ltd., trade name, softening temperature 70 ° C., hydroxyl value 30 m)
gKOH / g) 770 parts, ε-caprolactam blocked isophorone diisocyanate (blocked polyisocyanate crosslinking agent) 230 parts, and the same method as in Example 1 except that 300 parts of titanium white were used. 24 μm diameter
Was manufactured. The minimum viscosity of this powder coating is 60 Pa · s, and the heat flow time is 13
Minutes.

Comparative Example 4 (Production of Epoxy Resin Powder Coating) As a material, Epicoat 1004 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name, bisphenol A to epichlorohydrin type epoxy resin, softening temperature 70 ° C., (Average molecular weight 1400) 940 parts, Calcol 8098 (manufactured by Kao Corporation, stearyl alcohol, trade name) 50 parts, Disparon PL540 (manufactured by Kusumoto Chemicals, powdered vinyl polymer, trade name) 30 parts, C11Z-Azine ( Example 1 except that 15 parts of 2,4 diamino-6- [2'undecylimidazolyl- (1 ')]-ethyl-S-triazine manufactured by Shikoku Chemicals Co., Ltd. and 300 parts of titanium white pigment were used. A polyester resin powder coating having an average particle size of 23 μm was produced in the same manner. The minimum viscosity of this powder coating was 40 Pa · s, and the heat flow time was 6 minutes.

Comparative Example 5 (Production of Epoxy Resin Powder Coating) As a material, Epicoat 1004 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name, bisphenol A to epichlorohydrin type epoxy resin, softening temperature 70 ° C., Average molecular weight 1400) 940 parts, adipic dihydrazide 60 parts,
A polyester resin powder coating having an average particle size of 23 μm was produced in the same manner as in Example 1, except that 300 parts of titanium white pigment was used. The minimum viscosity of this powder coating is 65 Pa
S and the heat flow time was 10 minutes.

Comparative Example 6 (Production of Polyester Resin Powder Coating (Epoxy Resin Curing Agent)) As a material, Finedec M8860 (trade name, manufactured by Dainippon Ink Co., Ltd., acid value 35, softening temperature 60 ° C., number average) 700 parts of molecular weight 2000 powder), Epicoat 100
2 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name, epoxy equivalent 550-700, average about 2 epoxy groups) 300
Parts and 300 parts of titanium white, a polyester resin powder coating having an average particle size of 15 μm was produced in the same manner as in Example 1. The minimum viscosity of this powder coating is 70 Pa
S and the heat flow time was 11 minutes.

Coating test (preparation of coating film) SPC obtained by degreasing the powder coating materials of the above-mentioned Examples and Comparative Examples
Electrostatic powder coating was performed on a C-SB steel plate (0.8 × 70 × 150 mm) so as to have a cured film thickness of 50 μm, and heated at 180 ° C. for 30 minutes to form a coating film. Various tests were performed on each of the obtained baked coated plates.

Table 1 shows the test results of Examples and Comparative Examples.

[0032]

[Table 1] Table 1

Test Method Visual Finish Appearance: The visual finish appearance of the coating film was evaluated from the glossiness and smoothness according to the following criteria. ：: good, や: slightly bad, ×: bad Finish appearance (L value): WaveScanP manufactured by BYK
The L value was measured with rus. The smaller the value, the better the smoothness. Specular reflectance: Measured at 60 ° specular gloss according to JIS K-5400.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B05D 7/24 301 B05D 7/24 301R C09D 5/03 C09D 5/03 133/00 133/00 163/00 163/00 167/00 167/00 F-term (reference) 4D075 AA09 BB26Z BB93Z BB95Z DA06 DA23 DB01 DC01 DC11 DC18 DC38 EA02 EA19 EB22 EB33 EB35 EB45 EB52 EB53 EB57 EC37 4J038 CG001 DB001 DD001 KA03 KA20 MA02 MA15 PA04

Claims (5)

[Claims] 1. A powder coating material which is cured by heating at 100 ° C. or higher, wherein the powder coating material melted by heating to a curing start temperature has a minimum viscosity of 0.1 Pa · s to 50 Pa · s. A thermosetting powder coating material having a flow time of 10 minutes or more. 2. The powder coating composition has an average particle size of 5 μm to 30 μm.
The thermosetting powder coating according to claim 1, wherein m is m. 3. The powder coating material has a heat softening temperature of 30 ° C. to 100 ° C.
The thermosetting powder coating according to claim 1 or 2, wherein the temperature is ° C. 4. The powder coating according to claim 1, wherein the powder coating comprises at least one resin selected from an acrylic resin, an epoxy resin, and a polyester resin, and a curing agent. The thermosetting powder coating according to the above. 5. A powder coating material which is cured by heating to 100 ° C. or more on an object to be coated, wherein the powder coating material melted by heating to a curing start temperature has a minimum viscosity of 0.1 Pa · s to 5 Pa · s.
A thermosetting powder coating having a heat flow time of 10 minutes or more is subjected to electrostatic powder spray coating, and then the minimum viscosity of the powder coating is 0.1 Pa · s to 50 Pa · s.
A method for forming a thermosetting powder coating film, wherein the coating is heated and cured at a temperature of 100 ° C. or more so that the flow rate becomes Pa · s and the flow time becomes 10 minutes or more.