JP2009215372A - Matte powdered coating material composition and method for forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matte powdered coating material composition which is excellent in low-temperature curability and water resistance and forms a coating film with stable luster and excellent surface smoothness, and a method for forming a coating film. <P>SOLUTION: The matte powdered coating material composition is obtained by dry mixing a plurality of powdered coating material compositions comprising a carboxyl group-containing polyester resin, a β-hydroxyalkylamide crosslinking agent, and calcium carbonate and barium sulfate as extender pigments. The method for forming a coating film includes applying the matte powdered coating material composition on a base material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a matte powder coating composition and a method for forming a coating film, which form a coating film having excellent low-temperature curability and water resistance, stable gloss, and excellent surface smoothness.

Powder paints are attracting attention as low-pollution paints because organic solvents do not volatilize into the atmosphere during painting. In particular, a polyester resin-based powder coating using a combination of a polyester resin and a crosslinking agent is known as a coating applied to metal products such as steel furniture, electrical appliances and automobile parts because of its excellent coating film performance. A matte coating film may be required to impart a high quality texture to these metal products.

  As a technique for adjusting the gloss in a polyester resin powder coating, a technique of adding a matting material such as silica or wax has been conventionally known. However, in order to adjust the 60-degree specular gloss of the coating film obtained by painting to a low gloss of about 30 to 40, it is necessary to increase the amount of matting material and wax, and therefore the surface smoothness is reduced. There is concern about the possibility of doing.

  Patent Document 1 discloses a polyester for powder coatings comprising an ungelled polyester having an acid value of 70 mgKOH / g or more, an ungelled polyester having an acid value of 10 to 50 mgKOH / g, and a hydroxylalkylamide curing agent. A resin composition is described. However, there is a concern that the gloss of the coating film fluctuates depending on the kneading conditions during coating production and the baking temperature after painting. Furthermore, when a moisture resistant load is applied to the coating film, there is a problem that whitening occurs or peeling occurs from the substrate.

Japanese Patent Laid-Open No. 10-7944

An object of the present invention is to provide a matte powder coating composition and a method for forming a coating film, which form a coating film excellent in low-temperature curability and water resistance, stable in gloss and excellent in surface smoothness.

The present invention
1. A matte powder coating composition obtained by dry-mixing a plurality of powder coating compositions containing a carboxyl group-containing polyester resin, a β-hydroxyalkylamide crosslinking agent, and calcium carbonate and barium sulfate as extender pigments,
2. 2. The matte powder coating composition according to item 1, wherein there are two types of powder coating compositions to be dry mixed,
3. The acid value of the carboxyl group-containing polyester resin contained in one powder coating composition is in the range of 10 to 40 mg / KOH, and the acid value of the carboxyl group-containing polyester resin contained in the other powder coating composition is 45 to 45 mg. The matte powder coating composition according to item 2, which is in the range of 200 mg / KOH,
4). The matte powder coating composition according to item 2 or 3, wherein a part or all of the carboxyl group-containing polyester resin contained in the powder coating composition is a branched polyester resin,
5. The mass ratio of the carboxyl group-containing polyester resin having an acid value of 10 to 40 mg / KOH and the carboxyl group-containing polyester resin having an acid value of 45 to 200 mg / KOH is in the range of 30:70 to 90:10 as a solid content. 5. The matte powder coating composition according to item 3 or 4, which is obtained by mixing two types of powder coating compositions so as to be inside. It is related with the coating-film formation method which paints the matte powder coating composition of any one of 1-5 on a base material.

The matte powder coating composition of the present invention can be obtained by dry-mixing a plurality of powder coating compositions containing a carboxyl group-containing polyester resin, a β-hydroxyalkylamide crosslinking agent and calcium carbonate and barium sulfate as extender pigments. Thus, it is possible to form a coating film having excellent low-temperature curability and water resistance, stable gloss, and excellent surface smoothness.

The matte powder coating composition of the present invention can be obtained by dry-mixing a plurality of powder coating compositions containing a carboxyl group-containing polyester resin, a β-hydroxyalkylamide crosslinking agent and calcium carbonate and barium sulfate as extender pigments. .

  In the present invention, dry mixing means so-called dry blending, and means a method of mixing two or more kinds of powders in a dry state without using a liquid dispersion medium. This dry mixing can be performed at room temperature, but it is preferable from the viewpoint of product quality and workability during production to be performed under a temperature condition below the melting point of the resin contained in the powder coating composition described below. In the case where there are a plurality of resins contained in the powder coating composition, it is preferable to perform dry mixing below the melting point of the resin having the lowest melting point. The melting point means a value measured by a differential scanning calorimeter (DSC) at a temperature rising rate of 20 ° C./min, and the softening point means a Vicat softening temperature obtained by the method of JIS K7206.

  In the present invention, the plurality of powder coating compositions to be dry-mixed each contain a carboxyl group-containing polyester resin. Specifically, it can be obtained by a polycondensation reaction by an ordinary method using an acid component mainly composed of monobasic acid or polyvalent carboxylic acid and an alcohol component as raw materials.

  In the present invention, it is particularly preferable from the viewpoint of low-temperature curability to use a branched carboxyl group-containing polyester resin synthesized by using a bifunctional component and a trifunctional component in combination. Here, the low temperature curability means that excellent coating film performance is obtained by heating and drying at 140 ° C. to 160 ° C. for 10 to 20 minutes.

  The acid component is not particularly limited, and examples thereof include monobasic acids such as benzoic acid, crotonic acid, pt-butylbenzoic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride. Dibasic acids such as acid, succinic acid, fumaric acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, maleic anhydride, itaconic acid, dimer acid, lower alkyl esterified products of these acids and trimellitic anhydride, A tribasic or higher polybasic acid such as methylcyclohexentricarboxylic acid or pyromellitic anhydride can be used.

  Moreover, it does not specifically limit as an alcohol component, For example, monohydric alcohols, such as methyl alcohol, ethyl alcohol, and butyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, 1, 4- butanediol, neopentyl glycol, 3- Dihydric alcohols such as methylpentanediol, 1,4-hexanediol, 1,6-hexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, ethylene oxide adduct of bisphenol A, glycerin, trimethylolethane, trimethylolpropane, A trihydric or higher polyhydric alcohol such as pentaerythritol can be used. These alcohol components can be used alone or in admixture of two or more.

  The esterification or transesterification reaction between the acid component and the alcohol component can be performed by a method known per se, for example, obtained by condensation polymerization of the acid component and the alcohol component at a temperature of 100 to 250 ° C. be able to.

  In the present invention, after obtaining a polyester resin having a hydroxyl group from the acid component and the alcohol component, to the hydroxyl group of the obtained polyester resin, maleic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, You may use what made the carboxyl group-containing polyester resin by introduce | transducing a carboxyl group in resin by making polybasic acids, such as hexahydro phthalic anhydride and tetrahydro phthalic anhydride, react.

  In the present invention, the plurality of powder coating compositions to be dry-mixed contain β-hydroxyalkylamide as a crosslinking agent for the carboxyl group-containing polyester resin. As β-hydroxyalkylamide, those having two or more functional groups per molecule are particularly preferred from the viewpoint of low-temperature curability and the moisture resistance of a coating film obtained by coating. For example, β-hydroxyalkylamide represented by the following formula can be used. (Here, n means an integer of 1 or more. From the viewpoint of low temperature curability and blocking resistance of the powder coating material, n is preferably in the range of 3 to 8, more preferably 4 to 4. Within the range of 6.)

  The blending ratio of the β-hydroxyalkylamide and the carboxyl group-containing polyester resin is arbitrary, but the equivalent ratio of the carboxyl group in the carboxyl group-containing polyester resin to the functional group of the β-hydroxyalkylamide is 1/0. It is preferable from the viewpoint of moisture resistance and boiling water resistance of the coating film obtained by coating that the blending ratio is in the range of 0.7 to 0.7 / 1, more preferably 1 / 0.9. Within the range of ~ 0.9 / 1.

  In the present invention, the plurality of powder coating compositions to be dry-mixed contain calcium carbonate and barium sulfate as extender pigments from the viewpoint of moisture resistance and boiling water resistance of a coating film obtained by coating.

  Calcium carbonate includes precipitated calcium carbonate (light tancal) obtained by chemical synthesis, and naturally produced calcium carbonate (heavy tancal) obtained by pulverizing marble, limestone, thorn skin, animal fossils and the like. Any of these can be used in the present invention.

  Barium sulfate includes pulverized barite minerals (barite powder) called natural barite and precipitated barium sulfate produced by chemical reaction. Precipitated barium sulfate can be used that allows the particle size to be selected.

  When the powder coating composition contains calcium carbonate as an extender and does not contain barium sulfate, the coating film obtained by coating has a disadvantage that the coating film gloss decreases when it is subjected to moisture and water resistance. May occur. Further, when barium sulfate is contained but calcium carbonate is not contained, there may be a disadvantage that the secondary adhesion is lowered when subjected to moisture resistance and water resistance load.

  As extender pigments, hydrous magnesium silicate (talc), magnesium carbonate, calcium sulfate (gypsum), diatomaceous earth, mica (mica powder), clay (kaolin), silica and the like may be used.

  As the extender, those having an average particle diameter of 0.01 to 30 μm are usually preferable, and those having an average particle diameter of 0.5 to 10 μm are more preferable. If the average particle size is larger than 30 μm, the appearance may be poor when the film is thin, and if it is smaller than 0.1 μm, melt dispersion may be difficult. The maximum particle size is preferably 200 μm or less, more preferably 50 μm or less.

  The above extender is a fine particle but has a strong surface activity and easily forms agglomerates, so that it has been surface-treated for the purpose of preventing aggregation and increasing affinity with vehicle-forming components. May be used. Surface treatment includes fatty acids and their salts, resin acids, other organic carboxylic acids and their salts and surfactants alone or in combination, treatment with titanate and silane coupling agents, inorganic acids, alkalis, Examples of the surface treatment include silica, alumina, and zinc compounds.

  The content of the extender pigment is not particularly limited, but in the range of 5 to 40 parts by mass with respect to a total of 100 parts by mass of the carboxyl group-containing polyester resin and the crosslinking agent, from the viewpoint of the smoothness of the resulting coating film. It is preferably within the range, and more preferably 10 to 25 parts by mass.

  In the present invention, the plurality of powder coating compositions to be dry-mixed may further contain a rust preventive pigment. As the rust preventive pigment, conventionally known pigments can be used for paints, and for example, aluminum phosphomolybdate, aluminum tripolyphosphate, zinc oxide (zinc white), and the like can be used. In particular, aluminum dihydrogen triphosphate can be used from the viewpoint of rust prevention and storage stability of the paint. Further, a pigment whose surface is treated with a compound such as zinc, calcium, sodium, manganese, tin, or titanium may be used.

  In this invention, when using a rust preventive pigment, the compounding quantity is 1 with respect to a total of 100 mass parts of the said carboxyl group-containing polyester resin and the said crosslinking agent from the point of the rust prevention property of a coating film, and smoothness. It is preferably within the range of ˜20 parts by mass, and more preferably within the range of 3 to 10 parts by mass.

  In the present invention, the plurality of powder coating compositions to be dry-mixed may further contain a color pigment. As the colored pigment, conventionally known pigments for ink and paint can be used alone or in combination of two or more. Specific examples of color pigments include metal oxide pigments such as titanium oxide and iron oxide, composite metal oxide pigments such as titanium yellow, carbon black, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, and perylene pigments. Perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, indigo pigments, and the like. .

  The blending amount of the color pigment is within a range of 1 to 150 parts by mass with respect to a total of 100 parts by mass of the carboxyl group-containing polyester resin and the crosslinking agent from the viewpoint of coloring power and finished appearance of the resulting coating film. It is preferable that it exists, More preferably, it exists in the range of 3-100 mass parts.

  In the present invention, a plurality of powder coating compositions to be dry-mixed include, in addition to the above-mentioned components, a glitter pigment, a fluidity adjusting agent, an antiblocking agent, and an ultraviolet absorption agent that are used in ordinary powder coatings as necessary. Agents, ultraviolet stabilizers, surface conditioners, anti-waxing agents, charge control agents, curing accelerators, epoxy resins and the like.

  In the present invention, the acid value of the carboxyl group-containing polyester resin in one type of powder coating composition among the plurality of powder coating compositions to be dry-mixed is in the range of 10 to 40 mg / KOH, and another 1 The acid value of the carboxyl group-containing polyester resin in the type of powder coating composition is preferably in the range of 45 to 200 mg / KOH from the viewpoint of gloss and smoothness of the coating film obtained by coating.

  A plurality of powder coating compositions to be dry-mixed according to the present invention can be produced by a known method. For example, the carboxyl group-containing branched polyester resin, a β-hydroxyalkylamide crosslinking agent, an extender pigment, and, if necessary, The components to be blended can be produced by melt-mixing, cooling and pulverizing, but they may be in the form of pellets cooled after melt-mixing. In that case, what is necessary is just to grind | pulverize, after measuring the pellet of several powder coating composition so that it may become a predetermined | prescribed ratio.

  Specifically, after mixing and dispersing the above components, using an extrusion kneader, uniaxial or biaxial extruder, etc., usually melt-mixed at about 80 to 150 ° C. to form a pellet and then cooled To do. This can be manufactured by finely pulverizing and classifying with an impact pulverizer, an airflow pulverizer or the like.

  The particle size of a plurality of powder coating compositions to be dry-mixed according to the present invention can be adjusted within the range of 10 μm to 80 μm in terms of volume average particle size. It is preferable from the point of appearance and smoothness, and more preferably in the range of 20 μm to 45 μm.

  A method for producing a matte powder coating composition by dry-mixing each of the powder coating compositions obtained above will be described. The mixing ratio of the plurality of powder coating compositions can be determined as follows.

  In the present invention, when there are two kinds of powder coating compositions to be dry-mixed, the matte powder coating composition obtained by mixing these powder coating compositions has an acid value of 10 to 40 mg / A plurality of powders so that the mass ratio of the carboxyl group-containing polyester resin in the KOH range and the carboxyl group-containing polyester resin having an acid value of 40 to 200 mg / KOH is in the range of 30:70 to 90:10 as the solid content. It is preferable to set the mixing ratio of the body coating composition. If the ratio of the high acid value polyester resin is higher than this range, the effect of lowering the gloss is not increased, and a large amount of an expensive crosslinking agent is added, resulting in an increase in raw material costs. Conversely, if the ratio of the high acid value polyester resin is lowered, it becomes difficult to sufficiently reduce the gloss.

  Specific examples of the dry mixing method include the following two methods. The first method is a method of measuring and mixing a powder coating composition of pulverized and classified powder particles so as to have a predetermined mixing ratio. For the pulverization, an impact pulverizer can be used, and for mixing, a container rotating type or a mechanical stirring type granular material mixer can be used. The second method is a method in which raw materials are melted and kneaded, and the cooled powder coating composition in a pellet state is measured, pulverized, and classified so as to have a predetermined mixing ratio. In this case, since the process of classifying from pulverization is performed once, it is preferable from the viewpoint of saving the process.

  In the coating film forming method of the present invention, a coating film having a thickness of 5 to 500 μm is formed on a substrate with the matte powder coating composition as a dry film thickness. Although the base material used in the present invention is not particularly limited, metal materials such as alloyed galvanized materials, cast iron materials, hot dip galvanized materials, magnesium alloy materials, aluminum die cast materials, and these metal materials Examples thereof include a material subjected to surface treatment such as degreasing and chemical conversion treatment, a plastic material obtained by applying a conductive primer and the like, and a processed product obtained by processing the material by various methods.

  The matte powder coating composition of the present invention can be applied to a substrate by known methods such as electrostatic coating, fluid dipping, spraying, in-mold, etc. It is preferable to employ the electrostatic powder coating method used. In the electrostatic powder coating method, after grounding the metal material as the base material, powder coating such as corona charging type coating gun, friction charging type coating gun, such as electrostatic electric field cloud flow immersion coating device made by Mesak Co., Ltd. It means a method of spraying a powder coating composition using an apparatus.

  When the corona charging type coating gun is used, the load voltage applied to the matte powder coating composition by corona discharge treatment is preferably -50 to -100 KV, more preferably -60 from the viewpoint of coating efficiency and finish. Set to ~ -90KV. On the other hand, when using a triboelectric charging gun, triboelectric charging may be performed so that the internally generated current value of the powder coating composition is 1.0 to 8.0 μA from the viewpoint of coating efficiency and finish. preferable.

  Moreover, the preferable discharge amount of each said coating gun is 50-400 g / min, and discharge pressure is 4.9 * 104-4.9 * 105Pa. Furthermore, the distance from the tip of the coating gun to the substrate to be coated is preferably 10 to 50 cm. By coating within these ranges, the particles of the powder coating composition can be coated efficiently and applied to the conductive substrate. The powder coating layer can be formed by electrostatic adhesion.

Next, an Example is given and this invention is demonstrated more concretely. Here, “parts” and “%” mean “parts by mass” and “% by mass”, respectively.

1) Into a reaction apparatus equipped with a synthesis thermometer, a stirrer, a pressurizing apparatus and a rectifying column for polyester resins 1 to 6, a part of neopentyl glycol, trimethylolpropane or adipic acid shown in Table 1 is added and stirred. However, after the temperature was raised to 130 ° C. and the liquid became transparent, 0.12 parts of monobutyl tin oxide and terephthalic acid were added as shown in Table 1 and the temperature was raised to 180 ° C. Next, the contents were heated from 180 ° C. to 240 ° C. over 4 hours, and after the temperature rising, the contents were kept at 240 ° C. until the solution became transparent. Thereafter, the rectifying column was replaced with a water separator, 60 parts of xylene was charged into the reaction apparatus, xylene was also charged into the water separator, and water and xylene were azeotroped to remove condensed water. Sampling was performed every 10 minutes from 30 minutes after the addition of xylene, and the acid value was measured. When the acid value shown in Table 1 (acid value at the time of stopping the reaction) was reached, heating was stopped. The acid value was measured by titrating with 1/10 N alcoholic KOH solution using pyridine as a solvent.

  Finally, xylene was removed under reduced pressure to obtain polyester resins 1 to 7 having a heating residue of 100%. The theoretical Tg (glass transition temperature), acid value, and Mn (number average molecular weight) of the obtained polyester resins 1 to 7 are as shown in Table 1.

2) Preparation of powder coating composition (pellet) Raw materials having the composition (parts by mass) shown in Table 2 were put into a high speed mixer (trade name, manufactured by Fukae Kogyo Co., Ltd., capacity: 2 liters), and agitator 500 rpm, The mixture is stirred and mixed uniformly at a chopper of 4000 rpm, then melt kneaded using an extrusion kneader (trade name, Busconyder PR46, manufactured by Busus) at a temperature of 80 ° C. to 150 ° C., cooled, Pellet-shaped powder coating compositions 1 to 11 before pulverization were obtained.

3) Manufacture of matte powder coating composition (dry mixing)
The powder coating composition produced in 2) is roughly pulverized with a hammer, weighed to the composition (parts by mass) shown in Table 3, finely pulverized with a hammer-type impact pulverizer, and then with a 200 mesh wire mesh By classifying, matte powder coating compositions used in Examples 1 to 16 and Comparative Examples 1 to 8 having an average particle size of 35 μm were obtained.

4) Preparation of test plate The matte powder coating composition obtained in 3) was coated with a base material (Nippon Parkerizing Co., Palbond #) using an electrostatic coating machine PG-1 (trade name, manufactured by Matsuo Sangyo Co., Ltd.). 0.8mm-thick SPCC steel plate treated with zinc phosphate at 3118) is coated with electrostatic powder so that the cured film thickness is 60 μm, and the material temperature is maintained at 140 ° C. for 20 minutes, 150 ° C. for 20 minutes Heat drying was performed under the three conditions of maintaining the material temperature and maintaining the material temperature at 160 ° C. for 20 minutes to obtain three levels of test plates for each of the examples and comparative examples. The evaluation results of the coating film performance of the obtained test plate are shown in Table 3.

The matting powder coating composition and the coating film forming method of the present invention can be applied to home appliances, steel furniture, building materials, road materials, automobile parts, and the like.

Claims (6)

A matte powder coating composition obtained by dry-mixing a plurality of powder coating compositions containing a carboxyl group-containing polyester resin, a β-hydroxyalkylamide crosslinking agent, and calcium carbonate and barium sulfate as extender pigments. The matte powder coating composition according to claim 1, wherein there are two types of powder coating compositions to be dry-mixed. The acid value of the carboxyl group-containing polyester resin contained in one powder coating composition is in the range of 10 to 40 mg / KOH, and the acid value of the carboxyl group-containing polyester resin contained in the other powder coating composition is 45 to 45 mg. The matte powder coating composition according to claim 2, which is in the range of 200 mg / KOH. The matte powder coating composition according to claim 2 or 3, wherein a part or all of the carboxyl group-containing polyester resin contained in the powder coating composition is a branched polyester resin. The mass ratio of the carboxyl group-containing polyester resin having an acid value of 10 to 40 mg / KOH and the carboxyl group-containing polyester resin having an acid value of 45 to 200 mg / KOH is in the range of 30:70 to 90:10 as a solid content. The matte powder coating composition according to claim 3 or 4, which is obtained by mixing two kinds of powder coating compositions so as to be inside. The coating-film formation method which coats the base material with the matte powder coating composition of any one of Claims 1-5.