JP2000219825A - Powder coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a powder coating material composition without causing the deterioration of adhesive strength due to permeation of water to a substrate- coating film interface. SOLUTION: This composition contains 100 pts.wt. powder coating material of a bisphenol type epoxy resin, e.g. a bisphenol A type or a bisphenol F type and 1-200 pts.wt. of a silicone resin having monomethylpolysiloxane as a main skeleton.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating composition and, more particularly, to a powder coating composition which is excellent in coating performance and can form a coating film exhibiting water repellency and barrier effect for a long period of time. It is about things.

[0002]

2. Description of the Related Art Epoxy resins have been mainly used in paints for indoor applications because of their good adhesion and reactivity to metal substrates.

[0003]

However, bisphenol-type epoxy resins, due to the water absorption of the resin itself, are particularly susceptible to the penetration of moisture into the interface between the base material and the coating film when immersed in warm water of 60 ° C. or more for a long time. There has been a problem with a decrease in adhesion.

[0004] It is an object of the present invention to provide a powder coating composition which does not cause a decrease in adhesion due to penetration of moisture into the interface between a substrate and a coating film.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a coating film is obtained by adding a silicone resin having monomethylpolysiloxane as a main skeleton to a powder coating containing a bisphenol type epoxy resin coating. At the time of formation, the present inventors have found that a silicone resin bleeds out on the surface layer of a bisphenol-type epoxy coating film to form a coating film having high water repellency and prevents the penetration of water under immersion in warm water, thereby completing the present invention.

That is, the powder coating composition of the present invention is characterized by containing 100 parts by weight of a powder coating containing a bisphenol type epoxy resin and 1 to 200 parts by weight of a silicon resin having a main skeleton of monomethylpolysiloxane. And

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

[0008] As bisphenol type epoxy resin,
Examples of the epoxy resin include bisphenol A, bisphenol F, and bisphenol S type. Among these, bisphenol A and bisphenol F are preferred from the balance between cost and performance. For use as a powder coating, the softening point is preferably 30C to 160C,
The temperature is more preferably from 50C to 150C, and from 60C to
Particularly preferred is 150 ° C. If the softening point is less than 30 ° C., it is difficult to maintain a solid at normal temperature, which is not preferable for use in powder coatings. On the other hand, if the softening point exceeds 160 ° C., the temperature during melt-kneading becomes higher than the reaction temperature, which seriously affects the performance of the coating film, which is not preferable. Further, the phase transition temperature is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, and particularly preferably 40 ° C. or higher. If the phase transition temperature is lower than 20 ° C., it is not preferable because the powder properties such as blocking deteriorate when stored at room temperature. In addition, these bisphenol-type epoxy resins can be synthesized by a known synthesis method.

Examples of the curing agent for bisphenol type epoxy resin include aromatic diamines such as diaminodiphenylmethane (DDM), condensates of aliphatic amines and aliphatic dicarboxylic acids, and amine curing agents such as polyamidoamine, dicyandiamide and imidazole. Acid anhydrides such as tetrahydrophthalic anhydride, benzophenone tetracarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, condensates of ethylene glycol trimellitate, decanedicarboxylic acid, isophthalic acid, and acid-terminated polyester resins Acid hardeners, Lewis acid metal complexes such as boron trifluoride metal complex, each having an average of phenolic hydroxyl groups per molecule of 1.
A phenolic curing agent having five or more phenols is exemplified.

[0010] The powder coating used in the present invention may contain a pigment and other additives in addition to the epoxy resin and the curing agent.

[0011] As the pigment, pigments usually used for paints can be used. For example, as a coloring pigment, titanium oxide,
Bengala, iron oxide, quinacridone, carbon black,
Examples mainly include azo compounds, dioxazine, indanthrene blue, metal complexes of phthalocyanine, and other metal salts. Examples of the extender include barium sulfate, silicon dioxide, talc, calcium carbonate, potassium titanate whiskers, aluminum borate whiskers, wollastonite, aluminum oxide, asbestos, ceramic powder, and the like. In addition, anticorrosive pigments such as hydroxyapatite doped with a metal such as strontium chromate, calcium and strontium can also be used.

The additives used in the present invention include leveling agents, waxes, defoamers, flame retardants, antioxidants, U
A V absorber or the like can be used normally. Modifiers include thermoplastic resins such as petroleum resins, urea aldehyde resins, terpenes, polyolefins, and the like.

Preferably, 0.5 to 100 parts by weight of a curing agent and 0 to 100 parts by weight of a pigment are added to 100 parts by weight of the epoxy resin.
After mixing 0.1 parts by weight and 0.1 to 20 parts by weight of an additive at room temperature, the mixture is kneaded using a kneading machine such as a single-screw or twin-screw extruder, which is commonly used in the production of powder coatings. The pellets formed by kneading are pulverized using a pulverizer such as a pin mill and adjusted to an arbitrary particle size distribution using a sieve or the like to obtain a powder coating.

As the silicone resin for bleeding out, a resin having a main skeleton of monomethylpolysiloxane is used. The molecular weight of the silicone resin is at least 10,000, preferably at least 11,000, more preferably at least 12,000. As the modification of the resin, the transfer rate from the paint mixture to the surface layer of the coating film can be adjusted by converting monomethylsiloxane as a structural unit to dimethyl or trimethyl, or modifying the resin with ether or ester.

The silicone resin is used in an amount of 1 to 2 with respect to 100 parts by weight of the powder coating containing the bisphenol type epoxy resin.
00 parts by weight, preferably 5 to 150 parts by weight, more preferably 10 to 100 parts by weight. If the amount is less than 1 part by weight, the transfer amount to the surface layer of the coating film is small, and a silicon film completely covering the bisphenol type epoxy resin powder coating film cannot be formed. On the other hand, if it exceeds 200 parts by weight, the film is transferred to the surface layer of the coating film, but becomes too rich in silicon, so that the physical properties as the original epoxy resin coating film cannot be exhibited.

After mixing these materials by a mixer, they are melt-kneaded using an extruder, and the obtained paint pellets are crushed by a crusher, classified and adjusted to an arbitrary particle size distribution to obtain a powder of the present invention. Obtain a coating composition.

The powder coating composition of the present invention can form a coating film by a conventional powder coating film forming method, and the silicone resin is coated on the surface of a bisphenol type epoxy resin powder coating film during the film forming reaction. And a coating film having excellent water repellency and barrier effect can be formed.

[0018]

The present invention will be described in more detail with reference to Examples. In the examples, parts represent parts by weight.

Example 1 2.5 parts of 2-phenylimidazoline was added to 60 parts of a bisphenol A epoxy resin (Epiclon 4050, manufactured by Dainippon Ink and Chemicals, Inc.) having an epoxy equivalent of 915 g / eq and a softening point of 100 ° C. Acrylic ester oligomer (manufactured by BYK; BYK360)
P) 1.0 part, 36.5 parts of titanium oxide were added, and a silicon resin having a main skeleton of monomethylpolysiloxane (manufactured by Wacker; Silres 610, molecular weight 12,000) 1
The powder coating composition A was prepared by adding 00 parts.

(Example 2) Bisphenol F type epoxy resin having a phenolic hydroxyl equivalent of 400 g / eq was added to 40 parts of a bisphenol F type epoxy resin having an epoxy equivalent of 800 g / eq and a softening point of 85 ° C. (manufactured by Toto Kasei Co., Ltd .; Epotote YDF-803). 22 parts of phenolic resin, 0.2 parts of propylimidazole as a catalyst, 1.0 part of an acrylic ester oligomer (BYK360P, manufactured by BYK), 25 parts of silicon dioxide as an extender, 10 parts of titanium oxide, 0 parts of carbon black .8 parts, and a silicone resin having a main skeleton of monomethylpolysiloxane (manufactured by Wacker; Silres6)
10 molecular weight 12,000) to obtain a powder coating composition B.

Comparative Example 1 2.5 parts of 2-phenylimidazoline was added to 60 parts of a bisphenol A type epoxy resin having an epoxy equivalent of 915 g / eq (manufactured by Dainippon Ink and Chemicals, Inc .; Epicron 4050), and an acrylic ester oligomer was used as an additive. A powder coating composition C was prepared by adding 1.0 part of BYK 360P (manufactured by BYK) and 36.5 parts of titanium oxide.

Comparative Example 2 2.5 parts of 2-phenylimidazoline was added to 60 parts of a bisphenol A type epoxy resin having an epoxy equivalent of 915 g / eq (manufactured by Dainippon Ink and Chemicals, Inc .; Epicron 4050), and an acrylic ester oligomer was used as an additive. BYK 360P) (by BYK, 1.0 part) and 36.5 parts of titanium oxide are added, and a silicone resin having a main skeleton of monomethylpolysiloxane (manufactured by Wacker; Silres)
(610 molecular weight 12,000) and 300 parts of a powder coating composition D were prepared.

Using the Randsburg Industry PG-1 type coating machine for the prepared powder coating compositions A to D,
A 3.2 mm-thick sandblasted steel sheet was coated at a static voltage of -80 kV to a thickness of 100 µm, and heated in a high-temperature machine heated to 180 ° C for 20 minutes to form a coating film.

The following evaluation was performed on the obtained coating film. Table 1 shows the results.

<Surface condition of coating film> Visual judgment.

<Impact resistance> According to JIS 5400 8.3 Punch diameter 1/2 inch Weight 500g Drop height.

<Storage Stability> The paint was left in a thermostat at 40 ° C. for one week, and then baked, and the resulting coating film was visually judged.

<Water repellency> At the point where the surface roughness of the coating film formed by each paint falls within + -2 μm, the water repellency was compared by the contact angle of water.

<Residual chlorine consumption> 70 × 12 on glass plate
Each paint was applied in an area of 0 mm and heated at 180 ° C. for 20 minutes to form a coated plate in water adjusted to a chlorine concentration of 1.2 mg / L so as to have a water contact area ratio of 500 cm ² / L. And left in a constant temperature room at 23 ° C. for one week. One week later, o-tolidine was used to perform a color test on the water containing each coated plate, and the chlorine concentration of the water was measured, and the amount of naturally volatilized chlorine in the test water without the coated plate subtracted was absorbed by the coating film. It was determined that the amount of chlorine was the same and compared.

<Temperature Gradient Test> A hot-rolled steel sheet having a thickness of 2.3 mm was subjected to sandblasting, and the powder coating compositions A to D were baked on only one side of the iron plate so as to have a thickness of 230 ± 30 μm. The uncoated surface was also coated with a rust preventive paint to a thickness of 20 μm or less. When the powder coating film side of the prepared coating plate was adjusted to 50 ° C. and the rust preventive coating side was adjusted to 25 ° C., the time until blistering was measured.

[0031]

[Table 1] Examples 1 and 2 using the powder coating composition of the present invention showed good results in all tests. On the contrary,
Comparative Example 1, which did not contain a silicone resin having monomethylpolysiloxane as a main skeleton, was poor in water repellency, residual chlorine consumption, and temperature gradient test. Comparative Example 2, which contained an excessive amount of a silicon resin having monomethylpolysiloxane as a main skeleton, had poor impact resistance.

[0032]

According to the powder coating composition of the present invention, it is possible to form a layer exhibiting water repellency and a barrier effect over a long period of time on the surface of the coating film while maintaining the excellent coating performance of the powder coating. .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiko Saito 1-12-19 Kitahorie, Nishi-ku, Osaka-shi, Osaka Inside Kurimoto Ironworks Co., Ltd. (72) Inventor Takaaki Exit 1-12-, Kitahorie, Nishi-ku, Osaka-shi, Osaka 19 Inside Kurimoto Iron Works Co., Ltd. (72) Kazuhito Hanano 1-12-19 Kitahorie, Nishi-ku, Osaka-shi, Osaka Prefecture 19-72 Inside Kurimoto Iron Works Co., Ltd. (72) Sachi Masuda 58-102 Hatanaka Honmachi, Iwakura City, Aichi Prefecture ( 72) Inventor Tetsuo Nagao 1-5-8 Takazadai, Kasuga City, Aichi Prefecture (72) Inventor Toshikazu Ikeda 5-45 Aikigaoka, Kani City, Gifu Prefecture (72) Inventor Susumu Nakai 309-7 Handa, Kaizuka City, Osaka Prefecture F term (reference) 4J038 DB061 DL032 MA02 NA07

Claims (1)

[Claims] 1. A powder coating composition comprising 100 parts by weight of a powder coating containing a bisphenol-type epoxy resin and 1 to 200 parts by weight of a silicon resin having monomethylpolysiloxane as a main skeleton.