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Metallic-colored thermoplastic molding material

Metallic-colored thermoplastic molding material description/claims

This application is a divisional patent application of U.S. patent application Ser. No. 10/495,099, filed Jan. 21, 2005, now U.S. patent Ser. No. ______, granted ______, and related to prior PCT Patent Application PCT/EPO1/12906, filed Nov. 8, 2001, and claims priority to and incorporates the aforesaid priority applications in their entireties by reference thereto.

1. Field of the Invention

The invention relates to a metallic-colored thermoplastic molding material containing metal glitter in various admixtures.

In addition, the invention relates to a method for manufacturing this molding material and use of a molding material according to the invention to manufacture molded bodies.

Metallic-colored thermoplastic molding materials are used, for example, in situations where plastics have displaced metal components, but for reasons of design it is important that the optical appearance of the molded bodies be adapted to the metallic structure of the former metallic components.

2. Background of the Prior Art

In principle, this adaptation can be accomplished in two ways: First, by using an expensive and costly subsequent coloration coating of the molded parts or, second, by using a molding material that already has the desired color effect. The second approach is preferred for economic and ecological reasons.

Such a metallic-colored thermoplastic molding material, from which the invention departs as prior art, is known from DE 197 28 914 A1.

What is disadvantageous in the molding material described there is that it tends to form visible flow lines during processing using the injection molding method, particularly when complicated molded parts with openings are manufactured. These flow lines impair the uniform perception of color and produce qualitatively poor molded part surfaces. As a result, not just the quality but also the usability of the molded piece is diminished.

The objective of the invention is to disclose a molding material with whose use this undesirable formation of flow lines does not occur, in order to thereby improve the quality of the goods manufactured. In addition, an objective of the invention is to disclose a method with which molding materials can be manufactured in which the final product manufactured from it is free of flow lines. Finally, an objective of the invention is to disclose a molded body with openings whose flow lines are not visible.

This objective is attained by the present invention in that the percentage by weight of metal glitter in the metallic-colored thermoplastic molding material is greater than 5% and less than or equal to 15%. In an especially advantageous embodiment of the invention, the percentage by weight of metal glitter in the metallic-colored molding material is preferably greater than 6%, in particular the percentage lies between 6% and 13%. Surprisingly, molded bodies that are fabricated from this type of molding material with a considerably increased percentage of metal glitter have no visible flow lines. At the same time, the mechanical properties are advantageously retained.

In a preferred embodiment of the invention, the molding material contains hexagonal metal glitter. The metal-glitter admixture is advantageously any mixture of square, rectangular and hexagonal metal glitters. As a result, the shape of the metal glitter is better adapted to naturally occurring crystalline lattice structures.

These metal glitters are coated in another embodiment of the invention, in order to intensify bonding to the base material and improve mechanical properties.

The objective is also attained in that, in an especially favorable embodiment of the invention, the molding material of this type contains a metal-glitter admixture whose edge-length distribution is not a Gaussian distribution.

It is advantageous if this distribution is at least monomodal, preferably bimodal or multi-modal, whereby “modal” in the sense of the invention means that only metal glitter particles of almost the same size and shape are present. Surprisingly, these types of admixtures produce a situation where the flow lines that are inevitably present no longer emerge optically in the final product and are therefore not visible.

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