Reactive blue 4

Reactive Blue 4 (CAS 13324-20-4), also known commercially as Procion Blue MX-R and Ostazin Brilliant Blue S-R, is a reactive dye that forms covalent bonds with substrate fibers to deliver durable, wash-fast coloration.

Where is Reactive blue 4 used?

• Textile processing: applied to cellulosic fibers like cotton, viscose, and linen under alkaline conditions
• Leather tanneries: through-dyeing and surface coloration where color fastness under wet conditions is a critical performance requirement
• Paper manufacturing: mass coloration and surface treatment of specialty papers where consistent hue and bleed resistance matter
• It also serves as a substrate in biochemical assays.

Good to know: Lab-grade material is used in enzyme substrate preparations requiring tighter purity specifications. Technical and laboratory grades are both available depending on the specific application and purity needs.

Commercial specifications

• Commercial dye concentrations standardized by dye content percentage