JP2003286445A - Method for manufacturing heat-curing powder water dispersion coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a heat-curing powder water dispersion coating composition. <P>SOLUTION: The method is characterized by combining a heat-curing base resin having a base resin such as an acrylic resin, a polyester resin, a fluororesin, a silicone resin, an epoxy resin, a amine-modified resin, a phenol resin, a urethane resin and the like introduced with a functional group such as a hydroxy group, a carboxy group, an epoxy group and an unsaturated group thereto with a curing agent having a functional group which is curable with these functional group, for example, such as a blocked ployisocyanate compound, a polyepoxide, a polycarboxylic acid compound, an acid anhydride, a carboxy group- and acid anhydride group-containing carboxylic acid compound, an amino resin, a phenol resin, a hydrazide compound, a peroxide and the like, melt-kneading the resultant to obtain a heatcuring powder resin composition and wet-dispersing the heat curing powder resin composition with a volume average particle diameter of 10-100 μm using a pipeline bead mill, thereby obtaining the heat-curing powder water dispersion coating composition having a volume average particle diameter of 5-20 μm. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a novel thermosetting powdery water-based dispersion coating composition. 2. Description of the Related Art In recent years, from the viewpoints of reduction of organic solvents, safety, and the like, there has been an increasing movement to replace water-based paints, which use a water-soluble resin as a main vehicle in the paints, with organic solvent-based paints. However, these water-based paints have many hydrophilic groups in order to dissolve the resin in the aqueous medium, so that the coating film is inferior in performance such as water resistance and should be adjusted to a high volatile concentration. Is difficult, so that it is easy to sag at the time of painting, and there is a problem in workability, and storage deterioration is apt to occur. [0003] Also, there have been proposed various water-based dispersion coating compositions in which the powder coating composition is dispersed in an aqueous medium.
However, this powder aqueous dispersion coating composition is prepared by first preparing a powder coating, and then dispersed in an aqueous medium by using a sand mill or the like, but when using a normal powder coating of about 40 to 60 μm, It is easy for sedimentation to occur during mixing in a mixing tank or the like, and it is difficult to disperse in water. At this time, there is a method of adding a water-soluble thickener to prevent sedimentation. In this case, as the powder coating material is pulverized by a dispersing machine such as a sand mill and made finer, the viscosity sharply increases. There's a problem. There is a means for dispersing a powder coating having a particle diameter of about 10 to 20 μm in water in advance, but it is costly to obtain a powder coating having this particle diameter. [0006] In the process of dispersing the powder coating material in an aqueous medium, the powder is prepared using a new dispersing machine capable of continuous water dispersion without causing sedimentation during preparation. An object of the present invention is to increase the production efficiency of a water dispersion paint. The inventor of the present invention has made intensive efforts to achieve the above object, and as a result of various studies, have found the present invention. An object of the present invention is to provide a method for easily producing a powdery aqueous dispersion coating composition by using a pipeline bead mill for a usual powder coating. [0008] In the water-based powder dispersion coating composition, as the thermosetting powder particles used for dispersing in water, a conventionally known thermosetting powder coating is used. be able to. Specifically, for example, as a base resin, an acrylic resin, a polyester resin, a fluorine resin, a silicon resin, an epoxy resin, an amine-modified resin, a phenol resin, a urethane resin, etc. Group, epoxy group, thermosetting base resin into which a functional group such as an unsaturated group is introduced, having a functional group that cures with these functional groups, for example, block polyisocyanate compound, polyepoxide, polycarboxylic acid compound, acid anhydride And a carboxylic acid compound containing a carboxyl group and an acid anhydride group, an amino resin, a phenol resin, a hydrazide compound, and a curing agent such as a peroxide. The raw materials listed as the base resin and the curing agent can be used alone or in combination of two or more. [0009] The thermosetting powder particles may also contain a coloring pigment, an extender pigment, a rust preventive pigment, a surface conditioner, a viscosity adjuster, and the like, if necessary. The powder coating composition thus obtained has a 50% cumulative particle size (measured using a Microtrac FRA (manufactured by LEEDS & NORTHHRUP)) having an average particle size of 40 to 60 μm. between. Next, a method of producing the powder coating resin composition by a pipeline bead mill will be described. A pipeline bead mill (manufactured by Inoue Seisakusho Co., Ltd.) is a vertical annular type bead mill as shown in FIG. 1, and a special rotor as shown in FIG. It is characterized by being obtained. The aqueous dispersion that has entered through the inlet pipe 5 descends between the outer peripheral portion of the rotor 1 and the inner wall of the vessel 2. During this time, the mixture is vigorously stirred with the media such as glass beads, and the powder coating particles are crushed. Further, the media is fed into the gap between the inside of the rotor and the screen surface through the lower portion of the rotor by the screw action of the spike-shaped projections on the outer peripheral surface of the rotor. Then, the centrifugal force separates the media with large specific gravity and the aqueous dispersion,
The media with a large specific gravity is returned to the gap between the outer peripheral surface of the rotor and the inner wall of the vessel through the slit. The mill base is discharged from the outlet pipe through the screen. In this way, the media is circulated from the outside of the rotor to the inside through the lower part of the rotor and from the inside to the outside through the slit by the effect of the screw action and the centrifugal force of the spike-shaped projections on the outer peripheral surface of the rotor. Due to the strong circulation of the media caused by the rotation of the rotor, a high flow rate treatment can be performed without uneven distribution of the media even in a highly concentrated aqueous dispersion. The circulating dispersion system using the pipeline mill as shown in FIG. 3 performs circulating dispersion at a high flow rate. Because of the high flow rate, sedimentation in the piping can be prevented. Further, the sensible heat of the aqueous dispersion cooled by the jacket through which the cold water flows in the circulation tank can suppress the temperature rise in the mill. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. Parts and percentages are each by weight. Preparation Example of Thermosetting Powder Coating Composition Polyester resin 6 having a softening temperature of 110 ° C. and a hydroxyl value of 30
0 parts, 9 parts of an ε-caprolactam block isophorone diisocyanate compound having an NCO of 15%, 30 parts of a titanium oxide pigment, 0.9 parts of a surface conditioner, and 0.1 parts of a curing accelerator are dry-blended with the above composition. (Henschel mixer), melt mixing and dispersion (biaxial extruder kneader), cooling, coarse pulverization, fine pulverization (atomizer), and filtration to produce a thermosetting polyester powder coating composition. Preparation Example of Thermosetting Powdered Water Aqueous Dispersion Coating Composition (Example) 100 parts of water was placed in a tank of a pipeline mill.
An aqueous medium was prepared by adding and dissolving 0.2 part of a nonionic surfactant having an LB of 12, 0.5 part of an antifoaming agent, and 0.2 of a preservative. Here, 100 parts of the thermosetting powder coating composition was added with stirring. At a peripheral speed of 10 m / s, glass beads (Hibee D16) were added at a filling rate of 80% into the vessel, and the inside of the circulating layer of the pipeline mill was maintained at 25 ° C.
Wet dispersion was performed until the average particle diameter became about 8 μm, and filtration was performed to obtain a thermosetting powder aqueous dispersion coating composition. One part of a thickener was added to 100 parts of the thermosetting powder aqueous dispersion coating composition to obtain the thermosetting powder aqueous dispersion coating composition. The volume average particle diameter of the obtained thermosetting powder aqueous dispersion coating composition is 7.3 μm, and the maximum particle diameter is 22.3 μm.
Met. The viscosity was measured at 20 ° C. (B-type viscometer:
The pressure was 1980 mPa · s at 60 rpm). Coating Film Test The thermosetting powder aqueous dispersion composition prepared as described above was applied to an SPCC SD (zinc phosphate treatment) plate by air spray. After leaving for 10 minutes after painting,
Keep the material temperature at 180 ° C for 20 minutes in a drying oven and
A baked film of 40 μm was obtained. Each coated plate was subjected to a 240-hour immersion test in a high-temperature water bath at 40 ° C. and a 4-hour immersion test in boiling water, followed by a 1 mm grid test.
When a peeling test was performed using cellophane tape, the example showed good adhesion. Moreover, the thing of an Example tests according to the salt spray test (JISZ-2371),
Creep width from cut (linear cut) 2.0 mm on one side
8F (AST)
M) Pass if: ) Showed good results. According to the present invention, it is possible to efficiently and easily produce a water-based powder dispersion coating composition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic sectional view of a pipeline bead mill used in the present invention. FIG. 2 shows a schematic sectional view of a rotor of a pipeline bead mill. FIG. 3 shows a schematic diagram of a dispersion system using a pipeline bead mill. [Description of References] 1, rotor 2, vessel 3, shaft 4, shaft seal 5, inlet pipe 6, screen 7, outlet pipe 8, slit 9, spike-shaped projection

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hiroyuki Matsumoto             4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa             Nishi Paint Co., Ltd. (72) Inventor Mutsuo Kuromoto             4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa             Nishi Paint Co., Ltd. F term (reference) 4J038 CD091 CG001 DA061 DA062                       DA112 DD001 DG001 DG302                       DL031 GA01 GA03 GA06                       GA07 JA35 JA66 JB17 KA03                       MA08 MA10 MA14 PA02 PA19

Claims (1)

Claims: 1. A thermosetting powder coating composition obtained by melt-kneading and having a volume average particle diameter of 10 to 100 μm is wet-dispersed using a pipeline bead mill to obtain a volume. A method for producing a thermosetting powder aqueous dispersion coating composition having an average particle diameter of 5 to 20 μm.