Process for plating plastic part after overmolding

Abstract

A plastic part is provided with decorative metallized surfaces as well as overmolded thermoplasticelastomer grip portions. The plastic part is overmolded with the TPE prior to metallizing the remaining exposed surfaces of the part. A TPE compound with saturated midblocks is used which is stable in the acid environment and elevated temperatures of the plating.

Description

BACKGROUND OF THE INVENTION[0001]This invention concerns a process for forming a plastic part, such as a case for a tape measure or other item in which there is a low-durometer grip portion and with other, rigid surfaces of the plastic substrate being plated with a shiny metallic coating. In particular, the invention is directed to a process in which the rigid plastic part is first subjected to an overmolding step to add the grip portion(s), and is then subjected to a plating or metallizing process. This process of overmolding first and then metallizing represents a significant improvement over the conventional technique of metallizing first and then overmolding, as it avoids scratching and damage to the shiny metal surfaces that can occur in the overmolding step.[0002]Metal plating of plastic materials is commonly done in the industry to provide a decorative, shiny metal finish to a molded plastic part. This can be done using an electroless plating technique or a combination of ele...

AI Technical Summary

Benefits of technology

[0006]Accordingly, it is an object of the present invention to provide a technique for forming metallized rigid plastic parts with overmolded grip portions, and which avoids the drawbacks inherent with the techniques of the prior art.

[0010]In a preferred embodiment, the thermoplastic elastomer is a compound having saturated elastomer midblocks and which is adapted to withstand exposure to the acid environment and elevated temperature of a plating bath. The decorative metal plating is carried out by preparing the exposed portions of the molded and overmolded substrate in a bath of chromic acid to etch the surface of said exposed portions. Then the substrate is subjected to electroless palladiumizing in a bath of stannous chloride and palladium chloride to produce a palladium tin layer on the surface of the exposed portions. A subsequent bath removes any plastic residue from the palladium tin layer on the exposed portions. Then the part is placed in successive plating baths of copper, nickel, and chrome for electroplating the palladium tin on the exposed portions, and produces a durable, shiny metal surface.

Problems solved by technology

Where the overmolding process is used for forming grip portions on a metal-plated plastic part, the action of placing the previously plated plastic part into the mold does often result in scratching or damaging to the other surfaces, including surfaces that are left uncovered by the overmolded grip portions.

These scratches are deemed unacceptable in the finished product, and so the parts or cases with scratching are scrapped.

However, because of the additional manufacturing steps involved in attaching the elastomeric grips, this technique increases manufacturing costs.

However, that objective has thus far eluded the industry.

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