| 摘要 |
A method for dyeing nylon filaments for use in wear-indicating toothbrushes includes immersing a batch of a first nylon filament for between 10 minutes and 80 minutes in an aqueous solution containing between 0.01% and 0.19% weight to volume of Indigotine dye, said solution having a pH between 1 and 7 and having a temperature between 50 DEG C. and 90 DEG C., the dye penetrating into the filament to color an outer cross-sectional region and not penetrating into an inner cross-sectional region of the filament; removing the batch of the first nylon filament from the solution, and repeating the steps for a batch of a second nylon filament, reusing the same solution.
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