JP2002020692A - Process for producing powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating which shows an excellent flow property, blocking resistance and coating efficiency and yields a smooth coated film showing a fine appearance. SOLUTION: A composite fine particle is obtained by subjecting a mixture of (A) a fine particle of a resin composition for powder coatings comprising a resin for powder coatings and a hardener or a fine particle of a resin for powder coatings and (B) at least one fine particle chosen from a hardener, an additive for powder coatings and a dyestuff to a frictional force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a powder coating material which provides a coating film which is excellent in workability, blocking resistance and coating efficiency, and which is smooth and excellent in appearance.

[0002]

2. Description of the Related Art Powder coatings are used in a wide range of fields instead of solution coatings because they do not generate volatile organic substances during baking and do not cause environmental problems such as air pollution. As a powder coating, an acrylic resin having a glycidyl group or a hydroxyl group and a curing agent (aliphatic dibasic acid, blocked isocyanate), a polyester resin having a carboxyl group or a hydroxyl group and a curing agent (block isocyanate, TGI
It is already known to use C), an epoxy resin and a curing agent (dicyandiamide, acid anhydride).

However, since conventional powder coatings are produced by simple mechanical pulverization, the particle shape is indeterminate and the powder flowability is not sufficient, so that the balance between the smoothness of the coating film and the anti-blocking property during storage is poor. There was a problem of chipping (for example, JP-A-47-26439). Therefore, methods for producing spherical particles by a suspension method (Japanese Patent Application Laid-Open Nos. Hei 9-157309 and Hei 9-100414) are disclosed. However, complicated operations such as washing, filtration, and drying of powder are required, and the production cost is reduced. It has the disadvantage of being expensive. Method of improving blocking resistance by adhering resin fine particles to powder coating (Japanese Patent Publication No.
JP-A-1222035 and JP-A-2-178361) are also disclosed, but there is a problem in the long-term blocking resistance because the core / shell structure is not perfect. A method of lowering the Tg of a resin for powder coatings and fixing a curing agent or the like by using an impact hitting means in order to improve the smoothness of the coating film (JP-A-8-1)
76468), but the spheroidization of the powder coating is not sufficient and there is a problem in powder fluidity. Further, a method of blending hydrophobic silica (JP-A-52-23133) to maintain the balance between the blocking resistance during storage and the smoothness of the coating film has been proposed, but the desired effects can be sufficiently obtained. It is not at present.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a powder coating material which is excellent in workability, blocking resistance and coating efficiency, which overcomes the above-mentioned disadvantages of the prior art, and which provides a coating film which is smooth and excellent in appearance. It is to provide a new manufacturing method.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors exerted a frictional force between the particles to form (A) the resin composition fine particles for powder coating or the resin fine particles for powder coating (B). )
By performing a complexing treatment with at least one kind of fine particles selected from a curing agent, an additive for powder coating and a pigment, the powder fluidity of the powder coating and the blocking resistance are improved, and the powder without the above-described disadvantages The inventors have found that a paint can be obtained, and reached the present invention. That is, the present invention provides (A) resin composition fine particles for powder coating or resin fine particles for powder coating comprising a resin for powder coating and a curing agent, and (B) a curing agent, an additive for powder coating and a pigment. The present invention relates to a method for producing a powder coating, characterized in that composite fine particles are obtained by applying a frictional force to a mixture with at least one type of fine particles selected from the group consisting of

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The resin for powder coating used in the resin composition fine particles for powder coating of the present invention and the resin fine particles for powder coating include polyester resin, epoxy resin, acrylic resin, phenol resin and the like. However, the present invention is not limited to these. The resin composition fine particles for powder coating of the present invention are composed of the resin for powder coating and a curing agent, but may contain other components.

The average particle size of the resin composition fine particles for powder coating and the resin fine particles for powder coating used in the present invention is preferably 5 to 60 μm.

The curing agents used in the present invention include polycarboxylic acids and anhydrides, metaphenylenediamine, metaxylylenediamine, dicyandiamide, aliphatic amines, alicyclic amines, melamine compounds, hydrazine compounds , Maleimides, cyanates, blocked isocyanates and the like, but are not limited thereto.

The additive fine particles for powder coatings used in the present invention include a melt flow regulator, a pinhole inhibitor, an ultraviolet absorber, an antioxidant, a curing catalyst, a plasticizer, a blocking resistance improver, and a powder. A body fluid imparting agent or the like may be pulverized if necessary, but is not limited thereto.

The pigments used in the present invention include:
Titanium oxide, phthalocyanine blue, phthalocyanine green, carbon black, iron oxide and the like,
It is not limited to these.

The blocking resistance improver used in the present invention includes acrylic resin fine particles and silica compound fine particles, but is not limited thereto.

The powder fluidizing agent used in the present invention includes, but is not limited to, silica compound fine particles.

The curing agent and pigment used in the present invention preferably have an average particle size of 0.01 to 10 μm. The average particle size of the powder coating additive fine particles is 0.0001 to 10
Although those having a thickness of μm are suitable, the blocking resistance improver and the powder flow-imparting agent are desirably 0.0001 to 3 μm.

Examples of the compounding device utilizing frictional force used in the present invention include a grinding type pulverizer and a particle sizer. For example, Mechanofusion manufactured by Hosokawa Micron Co., Ltd., Theta by Tokuju Kosakusho Co., Ltd. Composer, Inc.
Examples include, but are not limited to, a nebula sizer manufactured by Nara Machinery Co., Ltd., and a DMM mechanochemical device manufactured by K.C.K.

[0015]

The powder coating obtained by the method of the present invention is excellent in blocking resistance and powder fluidity and, when a coating is formed, provides a coating excellent in coating smoothness. it can.

[0016]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples.

Reference Example 1 Method for Producing Resin Fine Particles (Component A) for Powder Coating Methanol 2 was placed in a reactor equipped with a thermometer, a stirrer, a reflux condenser, a pressure regulator with nitrogen, and a bottom extraction tube.
Then, the mixture was heated to 103 ° C., and 35 parts of methyl methacrylate, 30 parts of glycidyl methacrylate, and styrene 1
5 parts, 20 parts of n-butyl methacrylate, and 4 parts of t-amyl par 2-ethylhexanoate were added over 2 hours, and the mixture was kept at the same temperature for 1 hour to obtain an acrylic resin solution. This resin solution was rapidly cooled under stirring to form a resin slurry solution, and then filtered and dried to obtain acrylic resin fine particles having an average particle size of 26 μm. The glass transition temperature of the obtained resin was 53 ° C.

REFERENCE EXAMPLE 2 Method for Producing Additive Fine Particles (Component B) for Powder Coating In a reactor equipped with a thermometer, a stirrer, a reflux condenser and a bottom extraction pipe, 100 parts of ion-exchanged water and 60 parts of methyl methacrylate were added. Part, Tween 20 (manufactured by ICI) 1 as emulsifier
Then, the mixture was emulsified sufficiently with stirring, and the temperature was raised to 70 ° C. Then 0.3 parts of potassium persulfate and 10 parts of ion-exchanged water
Of the solution was charged into a reactor and emulsion polymerization was carried out for 4 hours to obtain a polymethyl methacrylate (PMMA) emulsion. Further, after the emulsion was frozen to release the polymer component, washing and centrifugal filtration were repeated to obtain ultrafine PMMA particles. The particle size was 0.5 μm and the glass transition temperature was 103 ° C.

Reference Example 3 Method for Producing Resin Composition Fine Particles (Component A) for Powder Coating Methanol 1 was placed in a reactor equipped with a thermometer, a stirrer, a reflux condenser, a pressure regulator with nitrogen, and a bottom extraction pipe.
Then, the mixture was heated to 103 ° C., and 35 parts of methyl methacrylate, 30 parts of glycidyl methacrylate, and styrene 1
5 parts, 20 parts of n-butyl methacrylate, and 4 parts of t-amyl par 2-ethylhexanoate were added over 2 hours, and the mixture was kept at the same temperature for 1 hour to obtain an acrylic resin solution. After cooling this resin solution to 70 ° C., the curing agent kept at 70 ° C., 50 wt% of dodecane diacid, 1 wt% of melt flow regulator Polyflow S, 1 wt% of pinhole inhibitor benzoin
Was added and uniformly mixed, and then spray-dried to obtain fine particles of an acrylic resin composition having an average particle size of 40 μm. No gel material due to a crosslinking reaction was found in the obtained resin composition.

Reference Example 4 Method for producing fine particles of resin composition for powder coating (component A) Methanol 1 was placed in a reactor equipped with a thermometer, a stirrer, a reflux condenser, a pressure regulator using nitrogen, and a bottom extraction pipe.
Then, the mixture was heated to 103 ° C., and 35 parts of methyl methacrylate, 30 parts of glycidyl methacrylate, and styrene 1
5 parts, 20 parts of n-butyl methacrylate, and 4 parts of t-amyl par 2-ethylhexanoate were added over 2 hours, and the mixture was kept at the same temperature for 1 hour to obtain an acrylic resin solution. After cooling this resin solution to 70 ° C., the curing agent kept at 70 ° C., 50 wt% of dodecane diacid, 1 wt% of melt flow regulator Polyflow S, 1 wt% of pinhole inhibitor benzoin
After adding 50 parts of methanol solution containing and mixing uniformly,
It was supplied to a vent extruder to devolatilize methanol. The obtained powder coating composition is pulverized using an impact type pulverizer,
A powder coating having an average particle size of 28 μm was obtained. No gel product due to a crosslinking reaction was found in the obtained acrylic resin composition.

Example 1 Acrylic resin fine particles (described in Reference Example 1) 100 parts Melt flow regulator Polyflow S 0.5 parts Pinhole inhibitor benzoin 0.5 parts Curing agent dodecane diacid (pulverized to an average particle diameter of 1 μm) 25 0.5 parts of PMMA ultrafine particles (described in Reference Example 2) are subjected to a compounding treatment by frictional force between particles using a grinding type pulverizer. After coating with additive fine particles, etc.,
A spherical powder coating having an average particle size of 21 μm was obtained.

Example 2 Acrylic resin composition fine particles (described in Reference Example 3) 100 parts Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.) 0.5 part were subjected to a compounding treatment using a grinding type pulverizer, and powder was obtained. When the fine particles of the resin composition for coating were coated with a powder flow imparting agent, hydrophobic silica fine particles Aerosil R972, a spherical powder coating having an average particle diameter of 36 μm was obtained. It is considered that the powder coating material was reduced in particle size by the frictional force.

Example 3 Acrylic resin composition fine particles (described in Reference Example 4) 100 parts PMMA ultrafine particles (described in Reference Example 2) 0.5 part were mixed with a grinding type pulverizer to obtain resin fine particles for acrylic powder coating. Was coated with PMMA ultrafine particles as a blocking resistance improver, and a spherical powder coating having an average particle diameter of 30 μm was obtained from the irregular shaped powder coating composition fine particles.

Example 4 82 parts of polyester resin (FINEDIC M-8020 manufactured by Dainippon Ink and Chemicals, Inc.) 82 parts Polyflow S 0.5 part Benzoin 0.5 part Block isocyanate (Cleran UI manufactured by Bayer) 52.5 parts Titanium oxide 43 Part was uniformly dispersed at 90 ° C. in 200 parts of xylene, and then 0 ° C.
Was sprayed into 1,000 parts of methanol to obtain a slurry of the resin composition for powder coating, followed by filtration and drying to obtain fine particles of a polyester resin composition having an average particle diameter of 36 μm. No gel substance due to a crosslinking reaction was found in the obtained fine particles of the polyester resin composition. The composite treatment by mechanofusion is performed, and the above polyester resin composition fine particles 1
When 00 parts were coated with 0.6 part of Aerosil R972, a spherical powder coating having an average particle diameter of 36 μm was obtained.

Comparative Example 1 Acrylic resin fine particles (described in Reference Example 1) 100 parts Polyflow S 0.5 part Benzoin 0.5 part Dodecane diacid 22 parts were mixed with a Henschel mixer, and then melt-kneaded. The powder was pulverized with a pulverizer to obtain a powder coating having an average particle diameter of 20 μm.

Comparative Example 2 Acrylic resin fine particles (described in Reference Example 1) 100 parts Polyflow S 0.5 part Benzoin 0.5 part Dodecane diacid 18 parts Titanium oxide 30 parts were mixed with a Henschel mixer and then melt-kneaded. The product was pulverized with a mechanical pulverizer to obtain a powder coating having an average particle size of 20 μm.

Comparative Example 3 77 parts of polyester resin (FINEDIC M-8075 manufactured by Dainippon Ink and Chemicals, Inc.) 0.5 part of Polyflow S 0.5 part of benzoin 0.5 part of blocked isocyanate (IPDIad B-1530 manufactured by Huls) 22 parts of titanium oxide 30 After mixing with a Henschel mixer, the resin composition melt-kneaded was pulverized with a mechanical pulverizer to obtain a powder coating having an average particle diameter of 20 μm.

The powder coatings obtained in each of the examples and comparative examples were evaluated. The evaluation items are coating film appearance, gloss, Erichsen, impact resistance and adhesion for a coating film formed using a powder coating, and blocking resistance for the powder coating itself. The evaluation method is as follows. Coating appearance (smoothness) The surface condition of the coating is visually evaluated and determined. …: No abnormality is observed Δ: Slight unevenness is observed X: Gloss is observed considerably (60 °) According to JIS K5400 7.6. According to Erichsen JIS K5400 8.2. Impact resistance According to JIS K5400 8.3.2. Adhesion According to JIS K5400 8.5.2. The coating composition after storage at 40 ° C. for 7 days was evaluated according to the following criteria. …: No lumps were seen at all △: Lumps could not be grasped with fingers ×: Lumps could be grasped with fingers The evaluation results are shown in Tables 1 and 2.

Table 1 Example 1 Example 2 Example 3 Example 4 Film thickness (μm) 40 40 42 45 Baking conditions (° C. × min) 160 × 20 ← ← 180 × 20 Appearance of coating film (smoothness) ○ ○ ○ ○ Gloss (60 °) 96 97 95 91 Erichsen (mm)>7>7>7> 7 Impact resistance (cm) 50 50 50 50 Adhesion 100/100 100/100 100/100 100/100 Blocking resistance ○ ○ ○ ○

Table 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Film thickness (μm) 40 40 40 Baking conditions (° C. × min) 160 × 20 ← 180 × 20 Coating appearance (smoothness) × × × Gloss (60 °) ) 88 84 78 Erichsen (mm)> 7 6 6 Impact resistance (cm) 20 30 20 Adhesion 90/100 88/100 86/100 Blocking resistance × × △ From the results shown in Tables 1 and 2, The powder coating of the present invention is improved in powder properties and coating properties at the time of forming a coating film by performing a compounding treatment by frictional force. It can be understood that the appearance is excellent.

Continuation of the front page F term (reference) 4J038 CG001 DA041 DB001 DD001 DG262 HA446 JA01 KA03 KA08 LA07 MA02 MA13 MA14 NA01 NA10 PA02

Claims (7)

[Claims] 1. A resin composition fine particle for powder coating or a resin fine particle for powder coating comprising (A) a resin for powder coating and a curing agent, and (B) a curing agent, an additive and a pigment for powder coating. For a mixture with at least one type of fine particles selected from
A method for producing a powder coating, wherein composite fine particles are obtained by applying a frictional force. 2. The method according to claim 1, wherein the resin composition fine particles for powder coating and the resin fine particles for powder coating are spherical. 3. The method according to claim 1, wherein the fine particles of the resin composition for powder coating and the fine particles of resin for powder coating have an average particle size of 5 to 60 μm. 4. The method according to claim 1, wherein the average particle diameter of the hardener fine particles and the pigment fine particles is 0.01 to 10 μm. 5. The method for producing a powder coating according to claim 1, wherein the average particle size of the additive fine particles for a powder coating is 0.0001 to 10 μm. 6. The method according to claim 1, wherein the resin composition for powder coating or the resin for powder coating constituting the resin fine particles for powder coating is a thermoplastic resin having a glass transition temperature of 0 to 70 ° C. 7. The powder coating additive has a glass transition temperature of 70.
The method for producing a powder coating according to claim 1, wherein the powder is a thermoplastic resin fine particle or a silica compound fine particle at a temperature of from −150 ° C.