Cellulosic Fibre Hydrolysis Kinetics in Exhaust Dyehouse Operations
Exhaust cellulosic dyeing demands progressive alkali dosing and strict pH control to prevent glycosidic cleavage from destroying fabric bursting strength.
Vinyl Sulfone Fixation
Covalent Bond
Chemical reaction between a vinyl sulfone reactive dye and the hydroxyl groups of a textile fibre results in a permanent molecular attachment that resists bleeding. Vinyl sulfone fixation requires the presence of an alkali to convert the precursor sulfate ester into the reactive vinyl form. This transformation occurs typically at temperatures between 40 and 60 degrees Celsius, making it a versatile choice for both exhaust and continuous dyeing.
Bond strength develops.
Process Control
Control over the pH of the dye bath is the most critical factor for ensuring a high yield. During vinyl sulfone fixation, the rate of alkali addition must be slow enough to allow the dye to distribute evenly through the fabric before it binds. Uneven application leads to unlevelness that is difficult to correct without stripping the color.
Hydrolysis Limitation
Competition between the fibre and the water molecules in the bath can lead to deactivation of the dye. If the vinyl sulfone fixation is not managed correctly, a significant portion of the dye reacts with water instead of the cellulose. This unfixed dye must be thoroughly removed through multiple soaping stages to ensure wash fastness.
Fastness Property
Stability of the bond under acidic conditions ensures that the color does not fade when exposed to perspiration or atmospheric pollutants. Fabrics that have undergone proper vinyl sulfone fixation exhibit excellent wet fastness and shade consistency. This reliability makes the chemistry a staple for high-volume retail goods.