Colorants tinctorial strength

Color Tinctorial strength Solubility 25°C (g/100 ml) Stability to Compatibility with food constituents... 

The pigments are manufactured either by reaction of the dianhydride with an amine or N,N -diaLkylation of the diimide. They are characterized by high tinctorial strength, excellent solvent stabiUty, very good weatherfastness, moderate brightness, and range in color from red to violet. An exception is the dianhydride which is not stable to alkah. 

Paprika and its oleoresin are approved for use in foods in general where its appHcation as a color additive frequendy ovedaps its use as a spice. Both products have good tinctorial strength and are used at 0.2—100 ppm to produce orange to bright red shades. 

In addition to the color and the tinctorial strength, which ate very important factors for the molecular design of anthraquinone dyes, affinity for fibers, various kinds of fastness (light, wet, sublimation, nitrogen oxides (NO ) gas, washing, etc), and apphcation properties (sensitivity for dyeing temperature, pH, etc) must be considered thoroughly as well. 

Anthrimides. Despite the facts that anthrimides have excellent leveling properties and cover a wide range of colors from yellow to black, they have htde commercial importance because of their duller shades and lower tinctorial strength. However, the anthrimides are important intermediates for manufacturing anthrimidocarbazoles. Some examples of anthrimide dyes are Cl Vat Orange 20 [6370-69-0] (149), (Cl 6302S), Cl Vat Violet 16 [4003-36-5] (150) (Cl 65020] Cl Vat Black 28 [128-79-0] (151) (Cl 65010] and Cl Vat Red 48 [4478-06-2] (152) (Cl 65205) (Fig. 6). 

In the manufacture of colored papers, it is best to add the dyestuffs before addition of rosin size and alum. This is not always possible in continuous dyeing procedures where dyestuffs must be added to stock containing size and/or alum, and this may cause premature laking of the dyestuffs and subsequent loss of tinctorial strength and/or dullness of shade. The proper selection of dyestuffs can help to reduce these disadvantages. 

Commercially produced metal-substituted chlorophylls such as copper chlorophylls and copper chlorophyllins that can be obtained by chemical modification of natural chlorophylls have better stability, solubility, and tinctorial strength, but they cannot be considered natural food colorants and will be discussed later. 

Although chlorophyll and chlorophyllin colorants seem to be easily obtained, in practice their production as natural food colorants is rather difficult. The sensitivity of chlorophylls to certain enzymes, heat, and low pH, and their low tinctorial strength greatly limit their manufacture and application as food additives, principally when the pigments are isolated from the protective environment of the chloroplasts. The well-known instability of chlorophylls prompted extensive research for developing... 

Triphenylmethane dyes show inferior lightfastness properties. They are, however, still one of the most important groups of synthetic dyes due to their brilliance, high tinctorial strength, and low cost. Several reviews have appeared on di- and triphenylmethane dyes.1-5 However, the color-forming precursors — leuco dyes — have received less attention in the literature. 

The primary chemical aspect of a mesomeric pigment system concerns the correlation between tinctorial strength and extent of electron delocalization. A higher degree of conjugation in a molecule is associated with a bathochromic shift color strength improves with the intensity of absorption. A resonating system proliferates by ... 

After all differences in tinctorial strength are accounted for, any remaining deviation is due to the inherent difference in shade between the two pigments and cannot be eliminated by simply adapting the amounts. It is useful to describe the remaining color difference by referring to the CIELAB system. 

This pigment has little impact on the market today and is only occasionally found in printing inks or in office articles, for instance in colored pencils. Its shade is more reddish and its tinctorial strength superior to that of P.Y.l. The low specific surface area of the types which are still commercially available makes for good hiding in print. Solvent resistance and other fastness properties equal those of P.Y.l P.Y.2 is only slightly less lightfast than P.Y.l. 

P.Y.62 exhibits comparably low tinctorial strength. A 0.5% pigment concentration in HD PE is necessary to produce 1/3 SD colorations (containing 1 % Ti02), compared to the 0.17% pigment concentration required to afford equal depth of shade with the somewhat more reddish diarylide yellow pigment P.Y.13. 

P.Y.183 is bleed resistant in plasticized PVC, where its poor tinctorial strength is of some disadvantage. 1/3 SD samples (5% TiOz) require 1.64% pigment. Such systems provide a lightfastness which is equal to step 6 on the Blue Scale 1/3 SD transparent colorations correspond to step 6-7 on the Blue Scale. 

In polyamide, P.Y.190 is heat stable up to 270°C. In this medium, the pigment has a somewhat redder shade and demonstrates noticeably higher tinctorial strength than in HDPE. 0.3% of the commercially available type are sufficient to produce 1/3 SD colorations. 

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