JPS6232126A - Electroconductive coating composition for expanded plastic bead and its molding - Google Patents

Abstract

PURPOSE:The titled composition which does not cause deformation by dissolution or agglomeration and is excellent in electroconductivity, comprising an aliphatic linear urethane resin, a mixed solvent based on an alcohol solvent and a specified electroconductive substance. CONSTITUTION:An electroconductive paint composition is obtained by mixing an aliphatic linear urethane resin (A) of a number-average MW of 20,000-100,000 with a mixed solvent (B) comprising 60% or above alcohol solvent (e.g., isopropyl alcohol) and 40% or below aromatic solvent (e.g., toluene), at least one electroconductive substance (C) selected from among 60-85wt% fine metal powder (e.g., Ni powder) and/or an electroconductive substance, 7-20wt% carbon black and 50-70wt% graphite and 10-50pts.wt. flame retardant (D) [e.g., tris(chloro)phosphate]. Expanded plastic beads of an expansion ratio <=30 or a molding thereof is spray-coated with said composition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conductive coating composition, particularly a conductive coating composition for foamed plastic beads and molded articles thereof.

[Conventional technology]

Foamed plastic beads are lightweight and can be molded to a certain degree, so they are used for transporting parts, semi-finished products, and products in the electronics industry, precision equipment industry, measuring instrument industry, optical equipment industry such as cameras, as well as building materials and insulation materials. It is used as returnable boxes, packaging materials, etc.

[Problem that the invention seeks to solve]

However, foamed plastic beads and their molded products are easily charged with static electricity, which can cause electrostatic discharge problems for electronic devices and parts, and dust adhesion problems for precision instruments and measuring instruments. However, the scope of its use has been severely limited in applications where such problems are averse.

[Means for solving problems]

The present inventor conducted research with the aim of solving the problems of electrostatic damage and dust adhesion of the above-mentioned foamed plastic beads and molded products thereof, as well as expanding the scope of their use. As a result, we discovered that this problem could be solved by using foamed plastic beads and their molded products coated with conductive paint, and after conducting research on conductive paints, we found that ordinary acrylic conductive paints, etc. It has been found that when this method is applied, a ketone-based, aromatic hydrocarbon-based, or ester-based solvent is used, which causes the problem of dissolving or coagulating deformation of the foamed plastic beads and their molded products.

The present inventor has conducted further research on a solvent system that does not dissolve foamed plastic beads and molded products thereof, and therefore does not cause agglomeration and deformation, and a resin composition that has excellent solubility in the solvent system. The present inventors have discovered that the above problems can be solved by using a mixed solvent whose main components are an aliphatic linear urethane resin and an alcohol solvent.

That is, the present invention provides (A) an aliphatic linear urethane resin;
(B) mixed solvent containing alcohol solvent as main component, (C
) Foamed plastic beads made of fine metal powder and/or conductive metal oxide and/or carbon black and/or graphite, and conductive coating compositions for molded products thereof.

The foamed plastic beads and molded products thereof, which are the objects to be coated in the present invention, are made of ordinary plastics such as polystyrene,
Made of foamed polyethylene, etc., with a foaming ratio of 30@
Primary foamed products are molded into a predetermined shape using a pressure cooker, and low-foamed products (in a broad sense, the expansion ratio is 10 or less) are molded using a special injection molding process, which improves heat insulation, sound absorption, elasticity, weight reduction, etc. It is something that has been given new properties.

The aliphatic linear urethane resin used in the present invention is a common polyurethane lacquer such as Desmolac 4125 (
Desmolac 4200 (manufactured by Sumitomo Bayer Urethane), Takelac E-350A (manufactured by Sumitomo Bayer Urethane)
(manufactured by Ota Pharmaceutical Co., Ltd.) and Takelac E-365 (manufactured by Takeda Pharmaceutical Co., Ltd.) may be used, but from the viewpoint of painting workability, the number average molecular weight is 20.
,000 to ioo, ooo, and the mixed solvent is preferably an alcohol solvent, such as isopropyl alcohol, n-butyl alcohol, etc., and an aromatic solvent (such as xylene, toluene, etc.) as a co-solvent. Therefore, alcohol-based solvents are used when painting.
It is preferable that it is 0% or more. The conductive properties of the coating composition of the present invention include fine metal powders such as nickel, copper, iron, etc., metal oxides such as zinc oxide, tin oxide, etc., alloys having conductivity, and/or carbon black. and/or by uniformly dispersing graphite or the like in the resin.

The content of fine metal powder, metal oxide, and conductive alloy is preferably 60 to 85 parts by weight in the solid content of the paint, and the content of carbon black is 7% by weight in the solid content of the paint.
-20% by weight, graphite preferably 50-70% by weight.

In addition, in the coating composition of the present invention, colorants such as titanium white, organic pigments, organic pigments, etc. can be blended and dispersed as necessary to obtain any desired coating color. In addition, when used in buildings, flame retardancy is an essential requirement.

In such a case, flame retardancy can be imparted by blending 10 to 50 PHR of a flame retardant. Examples of easily dispersible flame retardants include tris(chlorotyl) phosphate, tris(dichloropropyl)° phosphate, condensed phosphoric acid ester, and tris(tribromophenyl) phosphate.

The coating composition of the present invention can be obtained by forming the above-mentioned components and uniformly mixing and dispersing them using a ball mill, an attritor, or the like.

The coating method of the coating composition of the present invention is not particularly limited, but foamed plastic beads can be spray coated in a fluidized bed,
For molded products, air spray painting is suitable.

Example 1 The conductive paint composition of the present invention was prepared by uniformly mixing and dispersing the following formulation in a ball mill.The conductive paint composition obtained was then applied to a foamed polystyrene molded product by air spraying. A coating film with a thickness of 10 μm was formed by air drying.

This molded product showed no deformation of the material, and when the surface resistance was measured, it was 1×10 Ω·cm, showing good antistatic properties.

Blend composition Aliphatic linear urethane resin 420 parts by weight (Desmolafuku 4125 (manufactured by Sumitomo Bayer Urethane)) Nickel powder 28.7 parts by weight Isopropyl alcohol 15.8 parts by weight n-butanol
15.3 parts 1 part toluene
15.8 parts by weight Dia Seventon Alcohol
3.5 parts by weight Example 2 The conductive coating composition of the present invention was prepared by uniformly mixing and dispersing the following formulation in a ball mill. Next, the obtained conductive coating composition was applied to a foamed polystyrene molded article by air spraying, and a coating film having a thickness of 20 μm was formed by air drying.

This molded product showed no deformation of the material, and when the surface resistance was measured, it was 1×ICI''Ω·1, showing good antistatic properties.

Blend composition Aliphatic linear urethane resin 306 parts by weight (Teramo Rhapta 4125 (manufactured by Sumitomo 7-41 Urethane Co., Ltd.)) Conductive zinc oxide 234 parts by weight Isopropyl alcohol 93 parts by weight n-butanol
93 parts by weight toluene
93 parts by weight Cyanine Green 5 parts by weight Example 3 The following formulation was uniformly mixed and dispersed in a ball mill to prepare a conductive coating composition of the present invention. Next, the obtained conductive coating composition was applied to a foamed polyethylene molded article by air spraying, and a coating film having a coating thickness of 10 μm was formed by air drying.

This molded product showed no deformation of the material, and the surface resistance value was measured as I x 10'Ω·l, indicating good antistatic properties.

Blend composition Aliphatic linear urethane resin 34.01 parts (Desmora Fuku 4125 (manufactured by Sumitomo Bayer Urethane)) Carbon black 10.0 parts by weight Isopropyl alcohol 100.0 parts by weight n-butanol 100.0 parts by weight Toluene
100.0 parts by weight Example 4 The following formulation was uniformly mixed and dispersed in a ball mill to prepare a conductive coating composition of the present invention.

The obtained conductive coating composition was spray-coated onto primary foamed polystyrene beads, air-dried, and then molded. Next, as a result of evaluating the flame retardancy of this molded product, the combustion rate of a molded product processed without coating with the conductive paint composition of the present invention was 1.15 (ml/5et); The combustion rate of the product coated with a conductive paint composition and molded was 0.5 (am/5ee), which ranked as self-extinguishing.

However, the combustion rate (m+a/5ec) is the distance in the direction of the self-limit indicator line (rhyme)/the time the flame reaches the self-limit indicator line (se
c).

Blend composition Resin group linear urethane resin 353 parts by weight Graphite 164 parts by weight Isopropyl alcohol 67 parts by weight n-butanol
67 parts by weight toluene
67 weight 1 part [Effect of the invention] By applying the coating composition of the present invention to foamed plastic beads and molded products thereof, conductivity is imparted to them without causing melting or agglomeration deformation, and problems caused by static electricity can be solved. Since it can be removed, the scope of application is expanded not only in the construction field, but also in fields such as the electronics industry, precision equipment industry, measuring instrument industry, and optical equipment industry such as cameras, and the use in these fields can be expected to expand.

Claims (1)

[Scope of Claims] (A) Aliphatic linear urethane resin, (B) mixed solvent containing alcohol solvent as main component, (C) fine metal powder and/or conductive metal oxide and/or, A conductive coating composition for foamed plastic beads and molded products thereof comprising carbon black and/or graphite.