JPH0649393A - Black zinc dust coating composition - Google Patents

Abstract

PURPOSE:To obtain a zinc dust coating compsn. improved in coloration and appearance without detriment to the storage stability, dilution stability and rust-proofing performance thereof, by blending a film-forming ingredient contg. a resin with zinc dust and conductive carbon black. CONSTITUTION:100 pts.wt. film-forming ingredient contg. a resin is blended with 50-86 pts.wt. zinc dust and 1-10 pts.wt. conductive carbon black to prepare a coating compsn. In this compsn. it is advantageous that the carbon black be dispersed together with the resin, and, if desired, a pigment dispersant, an anti-settling agent, a solvent, etc., with the use of a dispersion mill for coating material, such as a sand grinder, a motor mill, a roll mill or a ball mill before dispersion of the zinc dust.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel black zinc dust coating composition, and more particularly, to improve rust prevention and appearance which are preferably used in the fields of automobiles, electric fields, industrial steel equipment, etc. And a black zinc dust coating composition.

[0002]

2. Description of the Related Art Conventionally, many zinc dust coating compositions containing zinc dust have been put into practical use, such as one-component paint, two-component paint and three-component paint. Most of this zinc dust coating is composed of zinc dust and a resin component, and has excellent rust-preventing property due to the anticorrosion action utilizing the difference in ionization tendency between zinc and iron. . The anticorrosive property of the zinc dust coating material achieves its purpose by the anticorrosive property of the resin as the binder component and the anticorrosive property of the zinc dust pigment used in combination therewith. In order to maintain the rust preventive property of the zinc dust coating sufficiently and to keep the storage stability and dilution stability of the coating itself sufficiently, generally, as a binder, a polar group such as a carboxyl group which is easily reacted with zinc dust is used. A resin containing as few groups as possible is used, and zinc powder is mixed and dispersed in this resin, or the resin and zinc powder are put in separate containers and mixed at the time of use. There is. By the way, when coating industrial steel parts such as automobile parts and electric parts, which require rust prevention and good appearance, zinc powder paint is usually applied as the undercoat paint, and after drying, black paint etc. The method of coating and drying the above colored top coating composition is used. In other words, the two-coat one-bake system and the two-coat two-bake system are currently used. Such a 2 coat 2 bake system and a 2 coat 1 bake system are inevitable that the process is complicated and costly. Therefore, in order to simplify the coating process and improve productivity, Many attempts have been made to add carbon black or other coloring pigments therein and to omit the step of applying the topcoat paint. However, the method of adding carbon black or other coloring pigment to the zinc dust coating has a drawback that the rust preventive power is inferior because the proportion of zinc dust in the dry coating film decreases. Therefore, a method of reducing carbon black and other coloring pigments has been studied as a means for improving such a defect, but when carbon black and other coloring pigments are reduced, the originally intended color tone cannot be obtained. The problem arises. Further, a method has been proposed in which zinc powder and a conductive powder having a predetermined average particle diameter are added to a synthetic resin in a specific ratio (Japanese Patent Laid-Open No. 63-48365), but this method has rust prevention and corrosion resistance. Is excellent, but the average particle size is 100
Since the conductive powder having a particle size of up to 500 μm is used, there is a disadvantage that the coating surface of the industrial steel part becomes rough and the practicability is poor.

[0003]

Under the circumstances described above, the present invention is directed to storage stability, dilution stability, and storage stability of zinc dust coatings.
The purpose of the present invention is to provide a zinc dust coating composition having improved colorability and appearance without impairing the rust preventive power.

[0004]

Means for Solving the Problems As a result of intensive studies to develop a zinc dust coating composition having the above-mentioned preferable properties, the present inventors have found that a film-forming component containing a resin is
It has been found that the object can be achieved by a composition in which zinc dust and conductive carbon black are mixed in a predetermined ratio, and the present invention has been completed based on this finding.

That is, in the present invention, 100 parts by weight of the coating film-forming component containing the resin (A) is used, and (B) zinc powder 50 to
86 parts by weight and (C) conductive carbon black 1-10
The present invention provides a black zinc dust coating composition formed by adding parts by weight. Hereinafter, the present invention will be described in detail. In the composition of the present invention, the resin contained as one of the constituents in the coating film forming component used as the component (A) is not particularly limited, and resins conventionally used in paints such as epoxy resins and epoxies can be used. Any one of ester resin, polyester resin, urethane modified resin, chlorinated rubber resin, acrylic resin and the like can be selected and used.

The conductive carbon black used as the component (C) in the composition of the present invention comprises the above resin, a pigment dispersant optionally used, and a precipitate before dispersing the zinc powder as the component (B). It is advantageous to disperse it together with an inhibitor and a solvent by using a paint disperser such as a sand grind mill, a motor mill, a roll mill and a ball mill. At this time, the dispersity of the conductive carbon black is 0.05 to 20 μm in average particle diameter, preferably 0.1 to 10 μm.
Is desirable. This average particle size is 0.0
If it is less than 5 μm, the structure imparted to the conductivity of carbon black is lost and the conductivity is inferior. The object of the invention cannot be fully achieved.

As the conductive carbon black,
(1) Well-developed structure, (2) Small particle diameter, (3) Large surface area and many pores, (3), π
Those having properties such as a small amount of impurities trapping electrons and (4) advanced graphitization are preferable. Examples of such conductive carbon black include acetylene black, Ketjen black, and carbon black for resin produced in an oil furnace. In the composition of the present invention, the conductive carbon black as the component (C) is 1 to 10 parts by weight, preferably 2.5 to 7. parts by weight based on 100 parts by weight of the coating film forming component as the component (A). It is necessary to mix it in a ratio of 5 parts by weight. If the blending amount is less than 1 part by weight, the coloring strength will be poor and the desired color tone cannot be obtained, and if it exceeds 10 parts by weight, the corrosion resistance of the coating film will be deteriorated.

The zinc dust used as the component (B) in the composition of the present invention, when added as it is to a paint,
This leads to an unfavorable situation in which the stability in the paint is poor and the paint is not uniformly mixed. Therefore, in the production of coating material, the resin and conductive carbon black, and a pigment dispersant used as desired, a composition in which an anti-settling agent, a solvent and the like are dispersed, zinc powder is added, a dissolver,
It is desirable to disperse evenly with a strong kneader. In the composition of the present invention, the zinc powder of the component (B) is blended in a proportion of 50 to 86 parts by weight, preferably 60 to 75 parts by weight, based on 100 parts by weight of the coating film forming component of the component (A). It is necessary to. If the blending amount is less than 50 parts by weight, the effect of rust prevention is not sufficiently exerted, and
If it exceeds 5 parts by weight, the coloring power of the coating film will decrease. The black zinc dust coating composition thus obtained is coated by a conventional coating method, for example, air spray, airless spray, dip coating, roll coating, brush coating, and the like to form a coating film by drying. You can

[0009]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The physical properties of the coating film were evaluated as follows.

(1) Rust-preventing property The state of rust generation in the cross-cut portion of the coating film after the salt spray test (JIS Z-2371) was carried out for a predetermined time was examined and evaluated according to the following criteria. ⊚: No abnormality ○: Slight rust or blister is observed. Δ: Rust or blister is observed on the entire surface. X: Significant rust or blister is observed on the entire surface. (2) Color Tone An examination was performed using a Munsell book in comparison with a color sample. (3) Conductivity DIGITAL MULTITIMER manufactured by METXE
Was used to measure the surface resistance of the coating film, and the volume resistivity of the coating film was determined by the following formula.

[0011]

[Equation 1]

Example 1 First of all, conductive carbon black [COLUMBIAN CARBON JAPAN CO., LTD., Trade name CONDUCTEX 975].
7.6 g, Olven [Shiraishi Industry Co., Ltd., trade name] 5 g,
Disper BYK-160 [Big Chemie Japan
Co., Ltd., trade name] 10 g, epoxy ester resin varnish [Nippon Oil & Fats Co., Ltd., solid content 50% by weight] 200 g, methyl ethyl ketone 50 g and xylene 77.4 g were mixed and dispersed in a motor mill to obtain carbon. A paint having a black dispersity of 0.28 μm in average particle size was obtained. next,
Zinc dust-3 [Sakai Chemical Industry]
Co., Ltd.] (650 g) was added, and mixed by a dissolver for 30 minutes to prepare a coating composition. This coating material was 1 part by weight based on 100 parts by weight of the coating film forming component as carbon black and 85.8 parts by weight based on 100 parts by weight of the coating film forming component as zinc powder. In the test, first, the cold rolled steel sheet (JIS G-3141) was degreased with toluene, and then the coating thickness of the flat surface portion was 20 to 30 μm.
The coating composition was spray-painted so that it would be the same as above, and baked and dried at 150 ° C. for 20 minutes. Then, the physical properties of the coating film thus obtained on the cold rolled steel sheet were evaluated. The results are shown in Table 1.

Examples 2 to 5 and Comparative Examples 1 and 2 A coating material was prepared in the same manner as in Example 1 except that the amounts of carbon black and zinc dust were as shown in Table 1. The coating film physical properties were evaluated. The results are shown in Table 1.

[0014]

[Table 1]

From this table, it is apparent that the coating containing the conductive carbon black can give a black coating film without impairing the rust preventive property.

Examples 6 to 13 and Comparative Examples 3 to 10 First, each raw material except zinc powder was mixed according to the coating composition shown in Tables 2 and 3, and the mixture was mixed with glass beads for 2 hours by a sand mill. After dispersion, the glass beads were removed by filtration through a wire mesh of 80 mesh to obtain a black paint base. The dispersity of carbon black at this time was 0.5 to 10 μm in average particle diameter. Next, the zinc powder in the amount shown in Table 2 was added to each of the black paint bases and mixed for 30 minutes with a three-one motor mill to prepare paints. The coating film physical properties were determined in the same manner as in Example 1, and the results are shown in Table 4.

[0017]

[Table 2]

Note 1) Mitsui Toatsu Chemical Co., Ltd., trade name 2) Tokai Carbon Co., Ltd., trade name, conductive carbon 3) Shiraishi Industry Co., Ltd., trade name 4) Big Chemie Japan Co., Ltd. ), Product name 5) Sakai Chemical Co., Ltd., product name

[0019]

[Table 3]

Notes 1) to 5) above 6) Mitsubishi Kasei Co., Ltd., trade name, ordinary carbon black

[0021]

[Table 4]

[0022]

[Table 5]

As is clear from Table 4, even if the blending amount of carbon black is 2.5 to 10 parts by weight with respect to 100 parts by weight of the coating film forming component within the range of the present invention, the conductive carbon black is added. Comparative Examples 3 to 6 which are not used show a black color, but the rust resistance of the coating film is remarkably inferior, and the adverse effect of not using the conductive carbon black is clearly shown. Further, even if the amount of conductive carbon black added is 2.5 to 7.5 parts by weight within the range of the present invention, the amount of zinc dust added is outside the range of 50 to 86 parts by weight of the present invention. 7-10
It can be seen that, although a black color is obtained, the coating film is significantly inferior in rust resistance. On the other hand, Examples 6 to 1 in which the conductive carbon black content was in the range of 2.5 to 7.5 parts by weight and the zinc powder content was in the range of 50 to 86 parts by weight.
It can be seen that in No. 3, the coating film is excellent in rust prevention and has a black color.

[0024]

The black zinc dust coating composition of the present invention can be used without impairing the storage stability and dilution stability of the coating itself.
Since it is possible to maintain the conductivity of the coating film, it is an epoch-making product that significantly improves the rust-preventive properties of flat parts and edge parts and has coloring power. Suitable for coating in the field of manufacturing equipment.

Claims (1)

[Claims] 1. To 100 parts by weight of a coating film forming component containing (A) resin, (B) 50 to 86 parts by weight of zinc powder and (C).
A black zinc dust coating composition comprising 1 to 10 parts by weight of conductive carbon black.