Reactive blue 4

Reactive Blue 4 (CAS 13324-20-4, EC 236-363-9) is a dichlorotriazine reactive dye commercially known as Procion Blue MX-R and listed under CI 61205. It belongs to the anthraquinone class of reactive dyes and carries no assigned E-code, as it is not approved for food applications.

In textile dyeing, Reactive Blue 4 forms a covalent bond with cellulose fibres under alkaline conditions, producing wash-fast blue shades on cotton and viscose. It is also used in paper coloration and leather dyeing, where its reactive triazine group anchors the dye molecule directly to substrate hydroxyl or amino groups, improving durability over conventional direct dyes.

Reactive Blue 4 is supplied as a saline suspension and is subject to REACH registration requirements within the European Union. Procurement teams should confirm supplier compliance documentation, including Safety Data Sheets aligned with EU GHS standards, and verify batch consistency through spectrophotometric analysis prior to formulation use.