JPS58176227A - Antistatic treatment of expanded plastic molding - Google Patents

Abstract

PURPOSE:To produce an expanded plastic molding having excellent appearance and antistatic property, by attaching a conductive resin to the surface of a pre-expanded expandable plastic molding and subjecting the molding to main expansion in a mold. CONSTITUTION:Expandable plastic particles (e.g., polystyrene particles pre- impregnated with an easily volatile expanding agent such as butane or Freon. Then, the particles are immersed in a solution of a conductive resin [e.g., N,N, N-trimethyl-N-(beta-acryloyloxyethyl)ammonium chloride polymer] and dried to coat their surfaces with the conductive resin. Then, the coated resin particles are placed in a suitable mold and subjected to main expansion by heating to produce the titled molding prevented from being electrostatically charged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a foamed plastic molded product that is less likely to generate static electricity.

Foamed plastic molded products, such as expanded polystyrene,
It is lightweight and inexpensive, making it an indispensable material for packaging. However, these devices are easily charged with static electricity, and therefore some parts (such as integrated circuits) cannot be used due to dust adhesion or static electricity damage.

As a countermeasure, a method of incorporating a surfactant is known, but this method is difficult to prevent static electricity damage at low humidity. The method of kneading conductive substances such as carbon black and metals is effective, but it is expensive and
Moreover, since the molded product is colored dark, its aesthetic appearance is impaired.

According to the present invention, the appearance of the molded product does not change compared to an untreated product at a relatively low cost, and at a humidity of, for example, 40%R.
Provided is a method for manufacturing a foamed plastic molded product that can sufficiently prevent the generation of static electricity even at low humidity of 0H or lower.

The method of the present invention involves pre-foaming foamable plastic particles into which a gasifying expansion agent has been mixed beforehand, coating the surface with a conductive resin, and then main-foaming and molding in a mold. It is characterized by

Expandable plastic particles preloaded with a gasifying expanding agent are well known in the industry, and many are commercially available. These are manufactured, for example, by dissolving an expanding agent such as a hydrocarbon such as butane, pentane, or hexane, or a halogenated hydrocarbon such as freon into polystyrene particles. In the present invention, any such commercially available expandable plastic particles can be used, and the particles are not limited to so-called expanded polystyrene molded products as long as the method and principle of foam molding are common.

The conductive resin that can be used in the present invention refers to one having a conductive group, for example, a quaternary ammonium group, in the resin molecule itself. Examples thereof include N-(β-(
(meth)acryloyloxyethyl) -N, N, N
-) (meth) such as trimethylammonium chloride
Acrylic acid quaternary ammonium salt, N-(3-(meth)
(meth)acrylamide quaternary ammonium salts such as (acryloylaminopropyl)-N,N,N-)limethylammonium chloride, N-vinylbenzyl-N;

Homopolymers containing styrenic quaternary ammonium salts such as N,N-)limethylammonium chloride,
and copolymers of this monomer and other copolymerizable monomers, such as methyl (meth)acrylate, styrene, etc.

These conductive resins are used in the form of an aqueous solution or dispersion, with the addition of an interfacial agent to improve wettability to the plastic surface and/or an adhesive to improve adhesion of the conductive resin, such as SBR latex, if necessary. .

The method of the present invention is similar to the conventional method for manufacturing foamed plastic molded products, except that the pre-foamed plastic is immersed in the conductive resin liquid, dried, and then the main foaming is performed after the pre-foamed plastic is coated on the surface. There is no difference.

As mentioned above, the present invention is characterized in that the conductive resin is attached to the foamable plastic at the stage of pre-foaming, but the effect is sufficient if it is attached at the stage of unfoamed beads before pre-foaming. In addition, in order to obtain the desired effect, the amount of adhesion must be increased, but in that case, the beads adhere to each other, resulting in poor workability and making it impossible to produce a perfect molded product.

Furthermore, adhesion after molding is not suitable for continuous work, and the effect is insufficient because it adheres only to the surface of the molded product.

Example 1 Nium chloride polymer surfactant (wetting agent) l tt water 89
〃Put polystyrene that has been pre-foamed to about 30 times the size in the above solution, stir well, then take it out and dry it naturally or
Dry with hot air at ~60°C. Approximately 5 by molding after drying
A polystyrene molded product with 0 times foaming was manufactured.

The half-life and frictional charging voltage of the molded product at 20°C, 940% R, H are as follows.

Table-1 (Note) The measuring equipment is as follows.

When the molded product of the present invention was actually used, there was practically no negative effect due to static electricity.

Example 2 Styrene copolymer surfactant (wetting agent) l tt water 89
In the same manner as in Example 1, polystyrene that had been pre-foamed approximately 30 times was treated to produce a molded product.

The half-life and frictional charging voltage of the molded product at 20°C, 940% R, H are as follows.

When the molded product of the present invention was actually used, there was practically no negative effect due to static electricity.

Example 3 Polymer SBR latex 20 Surfactant (wetting agent) 1 Water
74 In the same manner as in Example 1, polystyrene that had been pre-foamed approximately 30 times was treated to produce a molded product.

The half-life and frictional charging voltage of the molded product at 20"C, 40% R, and H are as follows.

Table 3 When the molded products of the present invention were actually used, there was practically no adverse effect due to static electricity.

Patent applicant Hiroki Takeuchi
Isamu Kaji is represented by patent attorney Takao Akaoka.

Claims (1)

[Claims] An antistatic method characterized by pre-foaming expandable plastic particles pre-mixed with a gasifying expansion agent, coating the surface with a conductive resin, and then main foaming and molding in a mold. Method for manufacturing foamed plastic molded products.