METHOD OF PRODUCING ACID-BASIC INDICATOR FOR CREATING FLEXIBLE PH-SENSITIVE SYSTEMS Russian patent published in 2017 - IPC C09D5/00 

FIELD: chemistry.

SUBSTANCE: method of producing an acid-basic indicator dye is described, the composition of which is characterized by the chemical formula C₂₆H₁₈N₄S₂O₁₀Na₂ for the creation of flexible pH-sensitive systems operating in the range of pH=6.0÷9.0, comprising the steps of diazotizing the disodium salt of 4,4'-diaminostilbene-2,2'-disulfonic acid diluted with hydrochloric acid, adding an aqueous solution of sodium nitrite with stirring and cooling in a quantity equivalent to amin and azocoupling of the previously prepared solution of the diazonium salt of disodium salt of 4,4'-diaminostilbene-2,2'-disulfonate and resorcinol in sodium hydroxide solution, with subsequent isolation and purification of the precipitate of dark brown colour.

EFFECT: dye with improved consumer, technological, economic quality of dyeing is obtained: low production cost, high degree of dye use and strength of the resulting colour, fast response time, stability during sterilisation, storage stability.

1 cl