Method of tinting a plastic article

Abstract

A method of tinting a plastic article is provided. The method comprises the steps of (a) providing a plastic article comprising a thermoset or thermoplastic polymer; (b) contacting at least a portion of the surface of said plastic article with a treatment composition comprising at least one dye and water; (c) maintaining said portion of said plastic article in contact with said treatment composition for a period of time at least sufficient to form a tinted plastic article; (d) removing said tinted plastic article from contact with said treatment composition; and (e) rinsing said tinted plastic article with water to remove excess dye. The method is carried out in the absence of an organic solvent, without the need for fixing or further processing steps.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method of tinting a plastic article without the use of organic solvents. A plastic article such as a molded article of thermoplastic polyurethane or polycarbonate is contacted with a treatment composition which includes one or more dyes and water.BACKGROUND OF THE INVENTION[0002]Colored plastic articles can be prepared by means of incorporating (e.g., by means of compounding) pigments and / or dyes directly into the polymeric materials from which the articles are prepared. Such direct incorporation methods result in the colorant being dispersed substantially throughout the molded article. Direct incorporation methods are not particularly well suited for the preparation of molded articles that are only slightly colored or tinted (e.g., less than opaque), such as in the case of sunshade lenses. It is typically difficult to adequately and sufficiently disperse the small amounts of colorant required to prepare slightly colored...

AI Technical Summary

Benefits of technology

[0012]wherein the treatment composition is characterized by the absence of organic solvent. An advantage of the present invention is that it can be carried out without the need for fixing or further processing steps.

[0013]In an additional aspect the invention further involves a dye separation process after the dye operation is completed, the separation process including the further steps of:

[0014](i) contacting the treatment composition with particulate activated carbon to form a mixture of the treatment; composition and particulate activated carbon;

[0015](ii) isolating a dye-free liquid comprising water from the mixture; and

[0016](iii) adding at least one dye to the dye-free liquid, thereby forming a further treatment composition. This further processing is useful when recycling of the treatment composition is desired, such as for environmental reasons. It is also possible to dispose of the treated water, for example by sending the water to the drain for treatment in a water treatment facility.

Problems solved by technology

Such direct incorporation methods result in the colorant being dispersed substantially throughout the molded article.

Direct incorporation methods are not particularly well suited for the preparation of molded articles that are only slightly colored or tinted (e.g., less than opaque), such as in the case of sunshade lenses.

It is typically difficult to adequately and sufficiently disperse the small amounts of colorant required to prepare slightly colored or tinted plastic articles, by means of direct incorporation methods.

In addition, the resin of the master-batch will be exposed to at least two heat cycles (one during the preparation of the master-batch, and another during preparation of the dyed molded article), which can result in a final molded article having degraded physical properties, and, due to thermal yellowing, a color different from the one intended.

Additionally, the use of organic solvents can cause odor problems in the end product, necessitating an additional processing step of baking to remove the solvent.