Bismuth vanadate pigment

Pigment Yellow 184 formula BiVO or mixed crystals of TBiVO -TBi MoO  

Bismuth vanadate pigments are inorganic yellow pigments that have gained significant commercial importance over the last two 

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Recently, BASF placed a new reddish yellow bismuth vanadate pigment on the market (trade name Sicopal Yellow L 1600). 

The production process for bismuth vanadate pigments consists usually of a precipitation reaction followed by a calcination step. This calcination leads to an appreciable increase in particle size as demonstrated in Figure 30. The calcination step is different from producer to producer and can be completely absent depending on the precipitation process and the desired product properties. 

Bismuth vanadate pigments are used in the manufacture of lead-free, weather resistant, brilliant yellow colors for automobile finishes and industrial paints. They are suitable for the pigmentation of solvent-containing paints, water-based paints, powder coatings, and coil-coating systems. It can be mixed with other pigments... 

Recently, different producers have developed bismuth vanadate pigments for the use in plastics. These pigments are used in every type of polymer, especially in polyethylene and technical plastics. 

The annual production of bismuth vanadate pigments is now about 500 t. In the near future an increasing market of 1000 to 2000 t/a is expected. 

The actual volume of bismuth vanadate pigments is estimated to be around 12001 a and is steadily increasing. 

BASF and Cappelle also offer reddish bismuth vanadate pigments within their product range [3.112, 3.113]. 

All commercial bismuth vanadate pigments are based on pure bismuth vanadate with monoclinic or tetragonal structure. The most important properties of all bismuth vanadate pigments are... 

In the following the physical and coloristic properties of a pure bismuth vanadate pigment are given (Sicopal Yellow L 1100, BASE) ... 

Bismuth vanadate pigments are used in the manufacture of lead-free, weather resistant, brilliant yellow colors for automotive OEM and re-finishes, industrial and... 

Bismuth vanadate pigments are high-quality yellow pigments. They lie in the higher price range for inorganic pigments because the raw materials are relatively expensive. 

Bismuth vanadate pigments are insoluble in water and alkalies. Only in strongly alkaline media, e.g. mixtures with cement, will they sometimes show instability and undergo a change in shade. Acid media with a pH of less than 2 cause perceptible solubilization, depending on how well the pigment has been stabilized. 

Bismuth vanadate pigments have a much higher chroma than yellow iron oxide and nickel titanate pigments. In full shades and the palest tints, bismuth vanadate pigments show superlative fastness to weathering. 

Bismuth vanadate pigments exhibit very good light fastness in both deep and pale shades. They show excellent weather resistance in full shades, and are superior to lead chromate in this respect. In full shades they are comparable with the best organic pigments and have the greatest durability in deep reductions. 

About 95 % of the total volume of bismuth vanadate pigments is used in paint manufacture and about 5 % in plastics processing. This ratio may change however in the future in favor of plastics coloration. 

The chemistry of bismuth vanadate pigments makes them sensitive to acids. Ho v-ever, tests in which acids were applied to baking finishes under practical conditions have shown that the acid resistance of these pigments is normally comparable to that of a highly stabilized lead chromate. The application of bismuth vanadate pigments in powder coatings and coil-coatings should be tested in customer material, because in such cases - more than in standard liquid paint systems - the suitability depends on the total formulation. 

Thermostable bismuth vanadate pigments are available today with a heat stability of 260 to 280 °C. They exhibit very good fastness to light and weathering in plastics for outdoor use. In weathering tests on plastics pigmented with 0.5 % cadmium yellow or 1 % bismuth vanadate, the bismuth vanadate pigment was superior both under artificial conditions (Xenotest, 4000 h) and outdoors (5 years). 

Bismuth vanadate pigments exhibit low solubility in water. They can therefore be removed from wastewater largely by mechanical means, for example in wastewater treatment plants. An appreciable increase in water solubility occurs only at pH levels of less than 2. 

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