Diazo orange pigment prepn. - to obtain a product with good covering properties and reduced binder requirements

摘要

The novel prepn. of the diazo pigment of formula (I): i.e. C.I. Pigment Orange 34, comprises coupling tetrazotised 3,3'-dichlorobenzidien with 2 equivs. of 1-(p-tolyl)-3-methylpyrazolone-(5), present in pptd. form, in an inorganic acid medium. A good covering pigment obtd. having reduced binder uptake, unlike the product of US 3567707 which has high binder uptake. Compared with the process of DT 2302482, the present process is more rapid and less expensive.