JPS63312367A - Prime coating composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition for plastic materials for use in domestic appliances, etc., capable of affording electrically conductive film outstanding in antistatic mature, by formulating specified proportion of acetylacetone in a composition comprising organic binder and electrically conductive filler. CONSTITUTION:The objective composition can be obtained by formulating a total of 100pts.wt. of (A) 40-93pts.wt. of an organic binder and (B) 7-60pts. wt. of electrically conductive filler with (C) 5-40pts.wt. of acetylacetone. This composition is capable of giving such electrical conductivity that the surface resistance in an undried state immediately after coating 1-50mum thick on a molded product made of e.g. plastic material is 10<7>-10<8>OMEGA, thus enabling coating on insulation molded articles in high efficiency in terms of both time and space.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a conductive undercoat composition that provides a conductive film with excellent antistatic properties, particularly for use as a topcoat on an insulating coated surface such as a plastic material. This invention relates to an undercoat composition convenient for applying by electrostatic coating.

[Prior Art] Recently, there has been a demand for weight reduction in automobiles, home appliances, and various other industrial fields, and molded products made of plastic materials are often used instead of metal in terms of moldability and other functionality. It's starting to look like this.

In this case, it is necessary to paint the molded product made of plastic material for cosmetic reasons and for the purpose of protection, and it is desired that the finished product be beautiful and that the painting process be simple.

Generally, in the field of industrial painting, electrostatic painting is used because of its high paint usage efficiency, its suitability for automatic painting that can process large quantities of objects in a short time, and its excellent coating film performance. However, since plastic materials and the like are insulators, electrostatic coating has not been effective enough.

As a method to improve this drawback, it has been proposed to first apply a conductive undercoat to molded products such as plastic/plastic materials, and then apply a topcoat using electrostatic coating (Special Publication No. 5g-1689). Publication, JP-A-59-215
Publication No. 366).

Such conductive undercoat paints obtain conductivity through mutual contact of conductive fillers dispersed in an organic binder.

However, since the paint contains a large amount of organic solvent for a while immediately after application, the concentration of the conductive filler in the paint is low, so there are few opportunities for the fillers to come into contact with each other, and the conductivity of the paint may be insufficient. It is in.

Therefore, when applying conductive undercoat paint and topcoat paint continuously to a molded product made of plastic material, in order to effectively utilize the painting space, after applying the conductive undercoat paint,
It is desirable to be able to electrostatically apply a top coat immediately, but with conventional conductive undercoats, conductivity cannot be achieved unless the base coat is set at room temperature for at least 20 minutes. There was a drawback that electrostatic coating could not be carried out immediately and continuously.

[Problems to be Solved by the Invention] The present invention provides an undercoat paint composition that is conductive even immediately after application, when the paint contains a large amount of solvent, thereby significantly shortening the painting work time. The purpose is to

[Means for Solving the Problems] In order to solve the above problems, the present inventors added a specific substance to the coating composition system, and added it to the coating composition in the state of a low-concentration conductive filler immediately after application. As a result of intensive research, we finally found a substance that has such an effect and completed the present invention.

That is, the present invention is a paint comprising an organic binder, a conductive filler, and an organic solvent, wherein the total amount of the organic binder and the conductive filler is 100 parts by weight, and 7 parts by weight.
An undercoat coating composition comprising 5 to 40 parts by weight of acetylacetone as a film forming auxiliary element to a film forming element containing ~60 parts by weight of a conductive filler and 93 to 40 parts by weight of an organic binder. It provides:

The organic binder used in the undercoat composition of the present invention is
Any resin component that can form a continuous film after being painted on the surface of the object to be coated can be used, such as acrylic resin, polyester resin, vinyl resin, polyurethane resin, polyolefin resin, epoxy resin, and cellulose resin. Resin etc. can also be used.

When the undercoat composition of the present invention is used as an undercoat for electrostatic coating of plastics, it is recommended to use a resin selected from among the above resins that has good adhesion to the target plastic material. desirable. For example, when painting molded products made of polypropylene, chlorinated polyethylene, chlorinated polypropylene, polystyrene,
Ethylene-butylene-styrene ternary block copolymer, maleic anhydride copolymer of chlorinated polyolefin,
A modified ethylene-olefin copolymer obtained by graft-polymerizing maleic anhydride onto an α-olefin can be suitably used.

The conductive filler used in the present invention can be any fine powder that can be uniformly dispersed in the paint and has conductivity.For example, graphite, conductive carbon black, etc. Examples include Keratsuen Black (trade name) manufactured by Axi Corporation, Conductex 975 (trade name) manufactured by Columbia Carbon, etc., as well as conductive zinc chloride (trade name 23 manufactured by Hakusui Chemical Co., Ltd., etc.), oxidized Conductive titanium oxide coated with an antimony-doped tin oxide film (for example, Mitsubishi Metals' product name W-1, etc.), mica (Teikoku Kako Co., Ltd.'s product name MEC, etc.), potassium titanate whiskers (large plate), etc. Examples include powders of metals such as Dentol WK2US (trade name, manufactured by Kagaku Co., Ltd.), black iron oxide, aluminum, copper, zinc, and the like.

The particle size of these fillers is, for example, 20 μm or less, preferably 10 μm or less.

In the present invention, the usage ratio of the active binder and the conductive filler is 7 to 60 parts by weight, preferably 10 to 55 parts by weight, of which the total amount of the binder and the conductive filler is 141 parts by weight. It is necessary to use a material containing a certain amount of conductive filler.

If the usage ratio of the conductive filler in the total amount of the conductive filler and the organic binder is less than 7 parts by weight, the conductivity of the paint in the wet state or the conductivity after drying of the paint will increase. On the other hand, if the proportion of the conductive filler used exceeds 60 parts by weight, the flexibility and adhesion of the coating film will decrease, and the topcoat will be difficult to apply. This is undesirable because it may reduce the gloss of the subsequent coating film.

In the present invention, a non-conductive filler other than the above-mentioned conductive filler may be used in combination. Examples of the non-conductive filler include titanium oxide, zinc oxide, red iron oxide, yellow iron oxide, mica, talc, IJ)bon, and the like.

The type and amount of these non-conductive fillers are not particularly limited in the present invention, but as described above, the flexibility of the coating film,
The amount can be selected as appropriate and used within a range that does not reduce the adhesion and gloss of the top coat. Note that fillers other than conductive fillers need to be excluded from the above 100 parts by weight.

Further, although the composition of the present invention is an undercoat composition, a pigment may be added thereto if desired. Of course,
In this case as well, it is not included in the standard amount of 100 parts by weight, similar to the non-conductive filler described above.

In the present invention, in order to disperse conductive fillers, non-conductive fillers, etc. into an organic binder, a dispersion machine such as a dispersion machine, an attritor, a sand grind mill, a ball mill, etc., which are normally used for pigment dispersion in the paint field, is used. can be used as is.

In the conductive undercoat composition of the present invention, it is essential to use acetylacetone as all or part of the organic solvent component in the coating film forming element. The amount of acetylacetone used needs to be in the range of 5 to 40 parts by weight, based on 100 parts by weight of the total weight of the organic binder and conductive filler contained in the coating film forming element.

If the amount of acetylacetone is less than 5 parts by weight, the paint will not have electrical conductivity in an undried state, and the object of the invention will not be achieved. On the other hand, if more than 40 parts by weight is used, the effect of improving conductivity will be small, and in some cases, it may take a long time to dry, and the paint may absorb moisture during storage, causing the storage container to rust, which is not desirable. do not have.

In the present invention, there is no problem in using organic solvents other than acetylacetone for the purpose of adjusting viscosity for paint production and coating. Examples of organic solvents that can be used include aromatic hydrocarbon solvents such as benzene, toluene, and xylene, alcohol solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and butyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, Ketone solvents such as cyclohexanone, ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate, and isoamyl acetate, glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and ethylene glycol monoethyl acetate. A solvent may be used.

In the present invention, in addition to the above components, surfactants,
Various additives conventionally used in paints, such as surface conditioners and anti-settling agents, can be used as they are.

[Effects of the Invention] The conductive undercoating paint composition of the present invention can be applied by ordinary coating methods such as ordinary air spraying, airless spraying, dipping, electrostatic coating, and brushing, and can be applied to molded plastic materials, etc. By coating the product with a film thickness of 1 to 50 μm, a conductivity of 107 to 108 Ω can be obtained in the undried state immediately after application, and by drying at a temperature of room temperature to 120°C, it can be applied to plastic materials, etc. A continuous film with good adhesion can be formed.

The continuous film formed in this way has sufficient conductivity for electrostatic coating of top coats even in the wet state, making it easier to coat insulating molded products such as plastic materials in time and space than before. It has the advantage of being more efficient.

[Example] The present invention will be explained in more detail with reference to Examples.

Example 1 The following components were placed in a sand grind mill and mixed and stirred for 1 hour to uniformly disperse each component.

Chlorinated polypropylene resin solution: Toluene solution, heating residue 20% (manufactured by Sanin Kokusaku Pulp Co., Ltd., trade name: Super Chron F) 56
．． 8 parts by weight (Resin content: 11.4 parts by weight) Conductive titanium oxide: (manufactured by Mitsubishi Metals, trade name W-1) 11.4 parts by weight Toluene, 11.4 parts by weight After uniformly dispersing, the following components were added. Add and stir.

Toluene, 17.0 parts by weight Acetylacetone = 3.4 parts by weight The conductive undercoat paint thus obtained was air-sprayed onto a polypropylene automobile bumper so that the film thickness after drying was 10 to 15 μm, and then sprayed at intervals of 1 cm. A copper electrode plate with a diameter of 500V was brought into contact with the painted surface, a DC voltage of 500V was applied between the plates, and the electrical resistance of the coating film was measured over time using a mega tester (manufactured by Yokogawa Hokushin Electric Co., Ltd., trade name). When measured, as is clear from Table 2, 30 seconds after painting,
The electrical resistance value became 108Ω or less, and the conductive state became possible for electrostatic top coating.

Two minutes after applying the conductive undercoat, apply Primec No. 3000, a liquid type topcoat for automotive resin manufactured by Nihon Yushi Co., Ltd.
White (registered trademark) has a coating thickness of 20 to 30 after drying.
Using an electrostatic hand spray gun,
Wet-on-wet painting with KV voltage applied, 10
After setting to room temperature for a minute, the conductive undercoat and topcoat were simultaneously heated and dried at a temperature of 120° C. for 30 minutes. After cooling, from the polypropylene bumper, 15c
A plate measuring m x 10 cm was cut out and a coating film performance test was conducted. As a result, good results were obtained as shown in Table 3.

Examples 2 to 4, Comparative Examples 1 to 2 Conductive undercoat paints were manufactured in the same manner as in Example 1 using the formulations shown in Table 1, and were air-sprayed onto polypropylene automobile bumpers, etc., and coated over time. The electrical resistance of the film was measured, and a top coat was applied and dried by heating to perform a performance test. The results are shown in Tables 2 and 3.

As is clear from the results in Table 2, in all Examples 1 to 4, the electrical resistance value of the coating film became 10'Ω or less 30 seconds after coating, and the electrostatic coating of the top coat became possible. On the other hand, in Comparative Example 1 which does not contain acetylacetone, 1
It took 5 minutes for the resistance to decrease to 0.8Ω or less.

Moreover, even though Comparative Example 2 contains acetylacetone,
Since the amount of the inorganic conductive filler is less than 7 parts by weight based on 100 parts by weight of the total amount of the organic binder and the conductive filler, the conductivity required for electrostatic coating cannot be obtained even after 10 minutes. Ta.

In Comparative Example 3, the amount of inorganic conductive filler was 6 parts by weight based on 100 parts by weight of the total amount of organic binder and conductive filler.
Since the amount exceeds 0 parts by weight, the development of conductivity is good, but as shown in Table 3, the gloss, adhesion, impact resistance,
Coating film performance such as bending resistance is poor, making it impractical.

When the amount of acetylacetone exceeded 30 parts by weight with respect to the total amount of organic binder and conductive filler of 100 parts by weight, as shown in Comparative Example 2 in Table 4, the inner wall of the container corroded and rust occurred. .

(Margin below)

Claims (1)

[Claims] 1 A paint containing an organic binder, a conductive filler, and an organic solvent, where the total amount of the organic binder and the conductive filler is 100 parts by weight, and 7 to 60 parts by weight of the conductive filler and 93 to 40 parts by weight. An undercoat composition comprising 5 to 40 parts by weight of acetylacetone to 1 part by weight of a film-forming element containing an organic binder.