From the chemical structure, beta naphthol series pigments also belong to the monoazo pigment, but they use beta naphthol as coupling component and chromatography is mainly orange and red, yellow and orange to separate the monoazo pigment, so it is classified as beta naphthol series pigments.
The naphthol series pigments came out earlier, and the first variety appeared in 1885. Prior to this, beta naphthol was used as a component of ice dyed dyes to dye cellulose fibers such as cotton fibers. Since the dye produced on the fiber is insoluble in water, the C.I. pigment red 1 was obtained in 1885 by the coupling of diazonium salt with beta naphthol. The pigment, called "Para Red", is considered the first valuable synthetic organic pigment that was widely used in textile printing and dyeing at that time.
C.I. pigment red 3
C.I. pigment red 3, also called toluidine red, is one of the 20 largest organic pigments in the world, like pigment red 5. Its fastness to solvent is not high enough, such as its resistance to alcohol, aliphatic hydrocarbons, aromatic hydrocarbons and dibutyl phthalate fastness grade 3, ester and ketone fastness resistance worse.
Pigment red 3 is mainly used in air drying paint, and its color changes slightly with the size and distribution of particles. Therefore, pigment manufacturers usually provide a series of pigment products. The larger the shade, the more blue the shade, but the stronger blue light is chemically modified pigment red 3.
With coarse particles of pigment red 3 Modulation paint when in use, the generated film with longer drying time, the original gloss film will wrinkle, this phenomenon is unique to the pigment, called "toluidine red skin" phenomenon.
Panchromatic Toluidine Red products, light fastness and fastness to weathering is very good, but to join the two white pigment products after the fastness are sharply reduced. The pigment is preferably used with a full color or similar color depth for interior wall latex paint or short-term outdoor advertising and marking.
Pigment red 3 in baking enamel is very easy to bloom, only for the panchromatic and baking enamel, paint products only used at low temperature. Pigment red 3 is often mixed with molybdenum red.
Pigment red 3 in printing ink application is very limited, because the application performance of chromatography with the same series of naphthol AS pigments in ink in much better than it. Pigment red 3 is mainly used to modulate flexible ink. When used in offset printing ink, the glossiness of the product is poor, and the ink product is very sensitive to the organic solvent.
In plastic coloring, pigment red 3 can have the conditions for rigid PVC products and a small amount of added products, full color titanium dioxide after the light fastness of nearly.