JP2002256215A - Powder coating composition having excellent blocking resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating composition having excellent blocking resistance. SOLUTION: This powder coating composition having excellent blocking resistance is characterized by comprising 0.01-10 wt.% of an orthoacetic acid ester compound as a dehydrating agent component in a powder coating composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel powder coating composition.

[0002]

2. Description of the Related Art In recent years, the use of powder coatings containing almost no volatile substances, mainly solvents, has been rapidly increasing from the viewpoints of pollution prevention and protection of the global environment.

[0003] The powder coating has a problem in that the blocking properties are reduced because the particles are aggregated due to the humidity of the outside air and the weight of the inside of the container during transportation. In recent years, powder coatings having a small particle size have been used in order to satisfy high finishing properties, and this increases the surface area of the powder coating particles. There was a problem that the blocking property was reduced during transportation.

[0004]

Means for Solving the Problems The present inventors have intensively studied to solve such problems. As a result, they have found that the inclusion of an orthoacetate compound as a dehydrating agent in the powder coating composition provides a powder coating composition having excellent coating storage stability (blocking resistance). The invention has been completed.

That is, according to the present invention, an orthoacetate compound is contained in a powder coating composition in an amount of 0.01 to 1 as a dehydrating agent component.
The present invention relates to a powder coating composition containing 0% by weight and having excellent blocking resistance.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a conventionally known powder coating can be used as the powder coating.
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 that 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.

The curing agent is one in which 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, an amino group is used in a base resin containing a hydroxyl group. And a curing agent such as a blocked isocyanate compound containing a blocked polyisocyanate group (caprolactam block diisocyanate, etc.), and a carboxyl group-containing base resin containing a polyepoxide containing an epoxy group (triglycidyl isocyanate). And a curing agent such as a curing agent such as β-hydroxyethylalkylamide, and a curing agent such as a polycarboxylic acid containing a carboxyl group (such as dodecane diacid or trimellitic acid) in an epoxy group-containing base resin. Isocyanate group-containing base resin contains hydroxyl group Polyol curing agent (trimethylolpropane) and benzyl-4-hydroxyphenyl methyl sulfonium hexafluoroantimonate initiator and the like.

In the coating composition of the present invention, a pigment (for example, an organic pigment (for example, a quinacridone type such as quinacridone, an azo type such as pigment red, a phthalocyanine type such as phthalocyanine blue or phthalocyanine blue), an inorganic pigment (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 (e.g., red iron, strontium chromate, zinc phosphate, etc.), curing catalysts (dibutyltin diacetate, dibutyltin dilaurate, triethylamine, or diethanolamine, etc.), ultraviolet absorbers (benzophenone-based compounds, Benzotriazole compounds, salicylate compounds, oxalic anilide compounds, etc., UV stabilizers (hindered amine compounds, etc.), antioxidants (phenol compounds, organic sulfur compounds, phosphite compounds, etc.), surface conditioners, Additives such as an anti-bake agent can be blended.

The orthoacetate compound used in the present invention includes orthoacetate methyl ester and orthoacetate ethyl ester. These orthoacetate compounds can be used alone or in combination of two or more. The compounding ratio of the orthoacetic acid ester compound is preferably in the range of 0.01 to 10% by weight, and particularly preferably in the range of 1 to 5% by weight based on% of the powder coating composition. If the compounding ratio of the orthoacetic acid ester compound is less than 0.01% by weight, there is no blocking effect, and if it exceeds 10% by weight, the production becomes difficult.

The powder coating of the present invention can be prepared by a conventional method, for example, mixing a base resin, a curing agent, an orthoacetate compound and other components as necessary, dry-blending with a mixer, and then heat-melting and kneading. , Cooling, coarse pulverization, fine pulverization, filtration, a melt-kneading method or a freeze-drying method.

In the above method, the order of blending the base resin, the curing agent, the orthoacetate compound and other components, if necessary, and the method of dry blending are not particularly limited. If necessary, an orthoacetate compound may be blended with a dry blend of other components to dry blend.

The powder coating of the present invention has a softening temperature of about 30 ° C.
100 ° C, particularly preferably in the range of 40 ° C to 80 ° C. If the softening temperature is lower than about 30 ° C., the blocking resistance decreases, while if it exceeds 100 ° C., the appearance of the coating film (particularly, the smoothness of the coating film) decreases, which is not preferable.

In the present invention, the anti-blocking property means
After storing the powder coating in an atmosphere at 30 ° C. to 60 ° C. for one month, the fusion of the powder coating was evaluated. Those having good blocking resistance are those which do not cause fusing between powder coating particles or can be easily disentangled with a finger even if apparently fusing, and have no practical problem. Inferior properties are those in which the powder coating particles fuse together and cannot be easily disentangled with a finger or the like. Clogs or bumps on the coating.

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.

[0016]

According to the coating composition of the present invention, by blending the orthoacetate compound, the moisture which affects the blocking property reacts with the orthoacetate compound to reduce the moisture in the air, thereby reducing the water content after storage. It is considered that a powder coating having excellent blocking resistance can be obtained. Also, the orthoacetate compound is liquid at room temperature, but the compound is melt-kneaded together with the powder raw material for powder coating to produce a powder coating, so that the compound is uniformly dispersed in powder particles, so other It has a remarkable effect on blocking resistance without deteriorating performance.

[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 1 800 parts of an acrylic powder resin (FINEDIC A207S, manufactured by Dainippon Ink and Chemicals, Inc., trade name, epoxy group-containing acrylic resin), 200 parts of dodecane diacid, and 20 parts of orthoacetic acid methyl ester were placed at room temperature. After dry blending with a Henschel mixer, melt kneading was performed with an extruder. Next, after cooling, it was pulverized and filtered to obtain a thermosetting clear resin powder coating material having an average particle size of about 20 microns. The softening temperature of the powder coating was 51 ° C.

Example 2 A powder coating material of Example 2 was obtained in the same manner as in Example 1 except that methyl orthoester was changed from 20 parts to 50 parts. The softening temperature of the powder coating was 52 ° C.

Comparative Example 1 A powder coating material of Comparative Example 1 was obtained in the same manner as in Example 1 except that methyl orthoacetate was not added. The softening temperature of the powder coating was 52 ° C.

Comparative Example 2 Example 1 was repeated except that 20 parts of silica gel was used instead of 20 parts of orthoacetic acid methyl ester.
The powder coating of Comparative Example 2 was obtained. The softening temperature of the powder coating was 54 ° C.

Table 1 shows the blocking resistance and coating film performance of the powder coatings obtained in the above Examples and Comparative Examples.

[0023]

[Table 1] Table 1

Blocking resistance: The powder coating was heated at 30 ° C.
Store for one month. Thereafter, the blocking state of the powder coating was evaluated. The following evaluation criteria were used. ：: Little change from powder coating state before storage. Δ: Small soft lumps are formed. The mass can be easily unraveled by hand. ×: A large lump as a whole. Difficult to loosen by hand.

Conditions for forming a coating film: A 0.8 mm thick zinc-phosphated dull steel plate is coated with an epoxy-based cationic electrodeposition paint to a dry film thickness of 20 μm and baked. After baking an automotive midcoat surfacer on the film to a dry film thickness of 20 microns, # 400
It was sanded with sandpaper and drained and dried. Next, a Magiclon base coat HM-22 (manufactured by Kansai Paint Co., Ltd., metallic paint, trade name) is applied as a cured coating film so as to have a thickness of about 15 μm, and baked and cured at 140 ° C. for about 30 minutes in a drier for testing. Material. Next, a powder coating was applied to the surface of the material by electrostatic powder coating so as to have a film thickness of about 50 μm, and was cured by heating at 160 ° C. for 30 minutes in a drier. The following test was performed on the obtained coated plate.

Appearance of coated film after storage: powder coating at 30 ° C., 1
Store for months. The finished appearance of the coating film was evaluated based on the following criteria based on glossiness and smoothness.は is the same as before storage, △ is slightly inferior, and × is considerably inferior.

Coating workability after storage: powder coating at 30 ° C.
Store for one month. Using an electrostatic coating machine (PG-1; manufactured by Matsuo Sangyo Co., Ltd.), under a coating condition of -70 KV and a discharge rate of 150 g / min. The coating workability when the electrostatic powder coating was performed was evaluated according to the following criteria.は indicates no change from before storage, 塗装 indicates inferior coating workability as compared to before storage, and × indicates significantly poorer than before storage.

Claims (4)

[Claims] 1. A powder coating composition having excellent blocking resistance, characterized in that the powder coating composition contains 0.01 to 10% by weight of an orthoacetate compound as a dehydrating agent component. 2. The powder coating composition according to claim 1, wherein the powder coating composition is a thermosetting powder coating. 3. The powder coating composition has a heat softening temperature of 30 ° C. or less.
The powder coating composition according to claim 1, wherein the temperature is 100 ° C. 4. 4. The powder coating composition according to claim 1, wherein the powder coating composition is a powder coating obtained by melt-kneading a powder raw material for powder coating and an orthoacetate compound. A powder coating composition as described in the above.