Polyethylene, soluble dyes

In 1904 Bally obtained a bluish violet solid by alkali fusion of benzanthrone at approximately 220 °C. Two isomeric compounds were isolated by vatting the reaction mixture and filtering off a sparingly soluble sodium salt. Oxidation of the filtrate gave a blue vat dye, violanthrone (6.75 Cl Vat Blue 20), as the main component. The less soluble residue similarly afforded a violet product, isoviolanthrone (6.76 Cl Vat Violet 10). The formation of isoviolanthrone can be suppressed by carrying out the fusion in a solvent such as naphthalene or a polyethylene glycol in the presence of sodium acetate and sodium nitrite. Dyes of this type are often referred to as dibenzanthrones. 

Most carriers are aromatic compounds, and have similar solubility parameters to the polyethylene tcrephthalate) libers and to some disperse dyes. 

The use of different dyes which are soluble in polar and nonpolar solvent allows oxidized (polar) sites in polymers to be stained. Methylene blue, which is soluble in water, ethanol and polar solvents, penetrates part of the surface of oxidized polyethylene, whereas Sudan III, a red dye soluble in nonpolar solvents, is miscible with the apolar region on a polymer surface [487]. 

---