Inorganic pigments

Inorganic Pigment
Sudhansu Senapati

Inorganic Pigments
Inorganic pigments are metallic salts or Oxides; not based on carbon chains or rings.
Inorganic Pigments Particle shape
2
Agglomerate ParticlesAggregate ParticlesPrimary Particles
Cuboid Spherical Rod shaped Irregular shaped

Light & weatherfastness
Ability of a pigment to retain its color and chemical & physical factors intact in outdoor exposure.
o Pigments Chemical composition, structure, particle shape, size and concentration is
responsible for light and weatherfastness.
o Light is mostly responsible for color & gloss change and chalking of the film.
o Shorter wavelength radiation of sunlight acts with rain water and atmospheric oxygen to form
extremely reactive radicals (OH, HO2), which deteriorate the coating by oxidative attack.
o Pigments acts as a catalyst or itself undergoes chemical change in photochemical reaction.
3

Heat & Chemical Resistance
Ability of pigment to retain its chemical & physical characteristics after exposure to chemicals and
heat.
o Inorganic pigments, especially Oxides are chemically very stable thus have highly protective
effect on substrate.
o Sulfide based pigments oxidized by atmosphere to form sulfate which are washed in rain.
o TiO2 Pigment is responsible for chalking because of their photochemical activity.
o TiO2 Pigments can be stabilized by reducing the radical producing hydroxyl group on the TiO2
surface.
o Oxides pigments have better heat stable than sulfide pigments, Oxide hydroxides and
carbonates. 4

Inorganic Pigments : Classification
5
Inorganic Pigments
White Pigments
Colored Pigments Black Pigments
Specialty Pigments

White Pigments
o Pigments that contribute light-scattering properties to coatings are generally known as white
pigments.
o High refractive index
o Good in hiding
o Found as pigments and leads
o White lead is basically lead carbonate (2PbCO3 , Pb(OH)2)
o Lithopone pigment is mixture of barium sulfate (BaSO4) and Zinc sulfide (ZnS)
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White Pigments : Classification
8
White Pigments
Titanium Dioxide Zinc Sulfide Zinc Oxide

Titanium Dioxide (TiO2)Pigments
o Natural occurring oxide of titanium, chemical formula TiO2 (O=Ti=O)
o Generally occurs from modification of Ilmenite, Rutile and Anatase Pigment.
o TiO2 Pigment has wide range application in Coating, Sunscreen, Paper & Food etc.
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Physical Properties
Chemical Formula TiO2 (Ti + O - ), O = Ti = O
Other Name Pigment White 6 (PW6)
Specific gravity Rutile - 4.21, Anatase- 3.85 gm/cm3
Particle Size 0.2 to 0.3 µm
Particle Shape Spherical
Refractive Index Rutile – 2.7, Anatase – 2.55
Mohs Hardness 5.5 to 7.0
Heat resistance Rutile - 1800⁰C, Anatase 700⁰C

Types of TiO2
o Three types of TiO2 is found in nature:
o Rutile: Formed by crystallization of magma with high titanium and low iron contents;
most thermodynamically stable one.
o Anatase: Anatase is one of three mineral forms of titanium dioxide, it becomes a rutile
when it is exposed above 700 degrees centigrade.
o Brookite: orthorhombic variant of TiO2, which occurs four natural polymorphic forms.
o Titanium dioxide has eight modifications
o Rutile, anatase & Brookite produced by three metastable phase through syntheticall
(Monoclinic, tetragonal & Othorombic)
o Five high pressure forms (α-PbO2-like, baddeleyite-like, Cotunnite- like, Orthorhombic OI,
and Cubic phase) 11

Rutile / Anatase
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Rutile Anatase
Crystal system:-Tetragonal, Crystal Shape:-Acicular Crystal system:-Tetragonal, Crystal Shape:-Pyramidal
Thermodynamically most stable
Anatase is a type of polymorph which becomes a rutile when it
is exposed above 700⁰C
Most harder (Mohs Hardness- 6.5 to 7) Softer (Mohs hardness 5.5)
Highest density (4.21 gm/cm3 ) Lowest density (3.85 gm/cm3 )
Rutile has blue undertone Anatase has yellow undertone
High Absorbance properties (absorption band at <415 nm),
Used in outdoors
Low absorbance properties (absorption band at <385 nm), Not
recommended for outdoors
Refractive indices:- 2.7 Refractive indices:- 2.55
Photocatalytics Properties:- Low, UV resistance:- High Photocatalytics Properties:- High, UV resistance: Low
Tinting Strength and Hiding:-High Tinting Strength and Hiding:-Low
Manufacture process: Sulfate & Chloride Manufacture process: Sulfate
Cost: Expensive Cost: Lower than Rutile

Manufacturing process of TiO2
o TiO2 manufactured by two Process:
o Sulfate Process: Titanium dioxide produce by the reaction of titanium containing raw material
with Sulphuric acid at 150 to 220⁰ C.
o Chloride Process: Titanium containing raw material Chlorinated at 700-1200⁰C with Carbon
and Chlorine gas to produce titanium tetra chloride. The tetra chloride is oxidized at 900-1400⁰C
to form TiO2.
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Chloride Process
TiO2
Cl2C,
>700⁰C
TiCl4
O2
TiO2 + 2Cl2
>900⁰C
Sulfate Process
FeTiO3 + 2H2SO4 → TiOSO4 + FeSO4 + 2H2O
TiOSO4 + (n+1)H2O → TiO2•nH2O + H2SO4
TiO2•nH2O → TiO2 + n.H2O

Sulfate Process
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Milling Digestion
H₂SO₄
Clarification Crystallization
Centrifuge
Vacuum
Evaporator
HydrolysisFiltration
Milling Titanium Dioxide
Ilmenite

Chloride Process
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Chlorine
Oxidizer
Coke
Chlorinator
Cooling Tower
Evaporator
Oxygen
Ore
Separator
TiO2

Sulfate / Chloride Process
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Sulfate Process Chloride Process
Long established and simple technology New technology
Uses lower grade, cheaper ores like Ilmenite Needs high grade ore like Rutile
Batch process Continuous process
More equipments and man power need Less equipments and man power need
Large amounts of waste materials
small amounts of waste formed with toxicity
problems: Cl2 and TiCl4
Pollution control expensive Recovery and recycling of chlorine possible
Produces anatase and Rutile pigments only produces Rutile pigments
Temp. 500-1100°C (Depends on pigment type) Temp. 1200-2400°C

Surface Treatment
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Base
Material
SP
CP
Inorganic
surface
Treatment
Filters Dryer
Milling
Organic
Surface
Treatment
TiO2
Inorganic surface treatment
Al2O3
SiO2
ZrO2
Organic surface treatment
Hydrophilic surface
Polyalcohol(Trimethyl propane, TMP)
Hydrophobic Surface
Polydimethyl Siloxane, PDMS

Nanoscale TiO2
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o Nanoscale TiO2 pigments is approximately 100 times finer than the TiO2 pigments.
o The production volume of Nanoscale TiO2 is less than 1 percent than TiO2 pigments
o Currently Nanoscale TiO2 are mainly used in High sun protection creams, textile fibers or wood
preservatives
Nanoscale TiO2 Pigments
Pigment
Code(Name)
Available form Primary particle size pH BET Surface Area
Zeta
potential
TiO2-70 Powder 33.4 nm 3.5 63 m2/g 48 mV
TiO2-120 Powder 12.5 nm 3.3 115 m2/g 52 mV
TiO2-40 Powder 42.3 nm 3.42 38 m2/g 49.5 mV
TiO2 Powder 27.2 nm 3.62 52 m2/g 14.1 mV
TiO2 Aqueous Suspension 17 nm 4.04 117 m2/g 51 mV

2. Zinc Sulfide & Oxide Pigments
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Zinc Sulfide Pigments
20
o Commercially, two types of Zinc Sulfide are available in market
o Lithopone: Produced by precipitation and subsequent calcination of a mixture of zinc sulfide
(ZnS) and barium sulfate (BaSO4)
o Used in primers, plastic masses, putties and fillers, artists color and emulsion paint.
o Used with combination of TiO2 pigments for good hiding, and it also used as pigment for
UV resistance paint.
o Sachtolith: Pure zinc sulfide is marketed as Sachtolith, Its produced by mixing of Na2S solution
with cobalt treated zinc salt solution.
o Used in Paint, Plastics, thermoplastics and as dry lubricates for fabrication.
o Both pigments has good bacterial and fungi resistance.

Zinc Oxide pigments
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o Zinc Oxide produced by three method
o Direct Process: By reduction of zinc ore into zinc vapors by coal and then oxidation of zinc
vapor into zinc oxide.
o Indirect Process: Zinc is melted and boiled; resultant vapor is oxidized by air combustion to
give zinc oxide.
o Wet Process: By Precipitation of zinc sulphate or chloride with carbonate, later washed and
calcined
o Used as biocidal, antifouling, anti corrosion and UV resistant additive in paint; Not used as
primary pigment.

Colored Pigments : Classification
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Colored Pigments
Oxide &
Hydroxides
Bismuth
Pigments
Ultramarine
Pigments
Cadmium
Pigments
Chromate
Pigments
Iron Blue
Pigments

1. Oxide and Hydroxide Pigments
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Oxide & Hydroxide : Classification
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Oxide and Hydroxide
Pigments
Iron Oxide
Pigments
Chromium Oxide
Pigments
Mixed metal
Oxide Pigments

1. Iron Oxide Pigments
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o Colors include from yellow, orange, red, brown, to black.
o Good in chemical and physical stability
o Nontoxicity
o Low Price
o Iron oxide pigments two types:
o Natural Iron oxide pigments
o Synthetic Iron oxide pigments

Natural Iron Oxide Ores
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Natural Iron Oxide Ores
Color Natural ore Formula Structure Color shift (by Increase particle size)
Yellow Goethite α-FeOOH Diaspore Green yellow to brown yellow
Red Hematite α-Fe2O3 Corundum Light red to dark violet
Black Magnetite Fe3O4 Spinel Black
Brown Maghemite γ- Fe2O3 Spinel super Brown
Umber
Iron Oxide +
Manganese
Oxide
Fe2O3 + MnO2 -
Raw umber: Deep brown to greenish brown
Burnt umber: Dark brown with red
undertone

Natural Iron Oxide Pigments
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Natural Iron Oxide manufacture Process
Beneficiation
Process
o Disaggregation: Size Reduction of ore
o Hydraulic washing: Separation of gangue from ore, its also called gravity separation
o Magnetic separation: Separation of gangue from ore by using their magnetic properties.
o Froth floatation method: Collectors and froth stabilizer are added to separate gangue from
the ore. Mostly used to remove gangue from sulfide ores.
o Leaching: Ore is treated with chemicals to convert the valuable metals within into soluble
salts while impurity remain insoluble
o Drying: Remove moisture by using different drying equipments
Fine Grinding
Process
o Milling: Reduction of particle size to very fine size

Synthetic Iron Oxide Pigments
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Synthetic Process
Laux Process
o Iron Oxides are obtained as a by-product of the aniline process.
o Used for production of Black and Yellow Iron Oxide.
o These pigments also used for preparation of Red Iron Oxide.
Calcination
Process
o High temperatures are required for this process (550⁰C to 1150⁰C).
o Used for Black Iron Oxide to oxidize in to Red or Yellow Iron Oxide.
o At very controlled conditions brown oxide pigments are obtained.
Penniman Process
o Iron Oxide obtained by reaction of metallic iron with oxygen in presence of acid catalysts.
o Used for production of very high quality red and black pigments.
Precipitation
Process
o Iron salts react with caustic soda in the presence of oxygen.
o Controlled temp., pH, purity, concentration and reaction velocity influence product quality
o Produces extremely high quality Pigments.

Natural / Synthetic Iron Oxide
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Natural Iron Oxide Synthetic Iron Oxide
Found in nature Man-made
Contain contaminants like clay and MnO Doesn’t contain any contaminants
Purity: Low, Cost: Low Purity: High, Cost: High
Tinting Strength : Low Tinting Strength : High (50% more than Natural)
Large Particle Size Small Particle Size
Poor Hiding Better Hiding
Limited Color Space Broad Color Space
Poor consistency in Properties Better consistency in Properties
Color of Ore deposits are variable by nature Manufacture keeps close color standards
Better in flow properties Poor in flow properties

Yellow Iron Oxide
o Natural occurring oxide of goethite , with structure α-FeOOH.
o Generally known as Geothite, loess and Ocher.
o Used in Coloration of Paint, Inks, cosmetics, paper industry etc.
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Physical Properties
Chemical Formula Fe2O3H2O
C.I. Name Pigment Yellow 42 & 43 (PY42 & 43)
Specific gravity 4 to 4.3 gm/cm3
Particle Shape Acicular
Refractive index 2.4
Mohs Hardness 5 to 5.5
Heat resistance 260⁰C

Manufacture: Yellow Iron Oxide
o Yellow Iron Oxide is manufactured using two process:
o Process for Natural Yellow Iron oxide:
o Process includes Beneficiation and fine grinding process
o Uses Goethite as ore
o Pigment Name: Pigment Yellow 43
o Process for Synthetic Yellow Iron oxide:
o Following processes are used to manufacture Yellow Iron Oxide (Pigment Yellow 42).
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Laux Process
2Fe + C6H6NO2 + 2H2O  2FeOOH + C6H5NH2
Scrap Iron
Yellow Iron
OxideNitrobenzene Aniline100⁰C

Manufacture: Yellow Iron Oxide
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Precipitation
Process
2FeSO4 + 4NaOH + ½H2O  2FeOOH + 2Na2SO4 + H2O
Iron(II) Sulfate
Yellow Iron
Oxide
Sodium sulfateCaustic Soda
10- 90⁰C
10-100Hr
Penniman Process
2Fe + ½ O2 + 3H2O  2FeOOH + 2H2
Scarp Iron Yellow Iron Oxide Hydrogen
Oxidation
Sulfuric acid
20- 50⁰C

Surface Treatment: Yellow Iron Oxide
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o Surface treatment enhances pigment properties and controls particle shape and
particle size distribution
o Two types surface treatment:
o Inorganic surface treatment:
o Alumina(Al2O3), Aluminium hydroxide Al(OH)3 & Silica (SiO2).
o Enhances the Dispersibility, heat stability and performance properties of
pigments
o Organic surface treatment:
o Aliphatic amines, hydroxyl carboxylic acids, aliphatic alcohols and polysiloxane.
o Enhances the Dispersibility in organic medium and hydrophobicity
Yellow Oxide Core
Inorganic modifiers
Organic modifiers

Properties: Yellow Iron Oxide
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o Colors – From bright yellow to very dull yellow as per purity.
o Generally green to red undertone.
o Excellent light & weatherfastness and solvent & chemical resistance; has high refractive
index thus better hiding
o Poor heat resistance
o Synthetic grades are used in Paint, Ink and cosmetic industry.
o Zinc ferrite (ZnFe2O4) based yellow oxide has better heat resistance(300⁰C)
o Nano scale yellow iron Oxide (Transparent yellow oxide)- Particle size 50 nm
o Used in Automotive metallic shade and transparent wood stain

Red Iron Oxide
o Natural occurring oxide of Hematite with chemical formula α-Fe2O3.
o Generally two type hematite uses as pigment; Oolitic hematite and hematite rose.
o Used in Coloration of Paint, plastics, rubber, ceramics, inks, paper, concrete, cement, etc.
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Physical Properties
Chemical Formula Fe2O3
Pigment Name Pigment Red 101 and 102
Specific gravity 4.2 to 5.3 gm/cm3

Manufacture: Red Iron Oxide
o Red Iron Oxide is manufactured using two process:
o Process for Natural Red Iron oxide:
o Uses hematite (Oolitic hematite and hematite rose) as ore.
o Pigment Name: Pigment Red 102
o Process for Synthetic Red Iron oxide:
o Following processes are used to manufacture Red Iron Oxide (Pigment Red 101).
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Calcination
Laux Process
2Fe3O4 + ½O2  3Fe2O3
Iron Oxide black Red Iron Oxide
800⁰C

Manufacture: Red Iron Oxide
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Calcination
Copperas Process
3FeSO4 + ½O2  Fe2O3 + 2SO3 +FeSO4
Iron(II) Sulfate Red Iron Oxide
Sulfur Oxides
Metal sulfates800⁰C
Penniman Process
Fe + 4HNO3 + Fe2O3 + Fe(NO3)2  2Fe2O3 + 4NO3 + NH4NO3
Scarp Iron
Red Iron Oxide
Nitrogen Oxides
Ferrous nitrate Nitric acid
Iron Oxide seed
Ammonium
nitrate
70- 90⁰C
Precipitation
Process
2FeSO4 + 4NaOH + Fe2O3 + ½O2  2Fe2O3 + 2Na2SO4 + 2H2O
Iron(II) Sulfate
Red Iron Oxide Sodium sulfate
Caustic Soda
Iron Oxide seed
80⁰C
pH 7

Surface Treatment: Red Iron Oxide
39
o Surface treatment enhances pigment properties and controls particle shape and particle
size distribution
o Alumina(Al2O3) and Silica (SiO2)
o Enhances the Dispersibility, stability and performance properties of pigments
o Amino-functional polysiloxane (amino propyl methyl siloxane – dimethyl siloxane co-
polymer).
Red Oxide Core
Inorganic modifiers
Organic modifiers

Properties: Red Iron Oxide
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o Colors – Paler red to dull brownish re as per purity and particle size.
o Yellow to blue under tone as per particle size change from smaller to larger.
o Over dispersion of pigment make them darker in shade.
o Excellent Heat, solvent and chemical resistance.
o High refractive index and better hiding
o Synthetic grades are used in Paint, Plastics, Ink and cosmetic industry.
o Nano scale Red iron Oxide (Transparent red oxide)- (Particle size 80 nm)
o Used in Automotive metallic shade and transparent wood stain

Black Iron Oxide
o Natural occurring oxide of Magnetite with chemical formula Fe3O4.
o It is a mixture of FeO and Fe2O3.
o Used in Coloration of Paint, plastics, rubber, ceramics, inks, paper, concrete, cement, etc.
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Physical Properties
Chemical Formula Fe3O4
Pigment Name Pigment black 11
Particle Shape Spheroidal

Manufacture: Black Iron Oxide
o Process for Natural black Iron oxide:
o Uses magnetite (mixture of FeO & Fe2O3) as ore.
o Process for Synthetic black Iron oxide:
o Following processes are used to manufacture black Iron Oxide .
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Precipitation
Process
2FeSO4 + 4NaOH + Fe + O2  Fe3O4 + 2Na2SO4 + 2H2O
Iron(II) Sulfate
Black Iron
Oxide
Sodium sulfate
Caustic Soda
Scarp Iron
90⁰C
pH 7
Laux Process
9Fe + 4C6H6NO2 + 4H2O  3Fe3O4 + 4C6H5NH2
Scrap Iron
Black Iron
OxideNitrobenzene Aniline
100⁰C

Surface Treatment: Black Iron Oxide
43
o Surface treatment enhances pigment properties and controls particle shape
and particle size distribution
o Alumina(Al2O3), Aluminium hydroxide Al(OH)3 and Silica (SiO2)
o Enhances the dispersibility and performance properties of pigments
o Phenyl methyl polysiloxane and hydroxyl carboxylic acids.
Black Oxide Core
Inorganic modifiers
Organic modifiers

Properties: Black Iron Oxide
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o Colors – Black with lower TS than carbon black.
o Brown to blue under tone as per particle size change from smaller to larger.
o Synthetic grades are used in Paint, Ink, rubber and cosmetic industry.
o Excellent weathering, solvent and chemical resistance but weaker in heat resistance.
o High refractive index and better hiding but poor in heat resistance.
o Manganese ferrites(FeMn2O3) based black iron oxide has better heat resistance (500⁰C)
o Nano scale black iron Oxide (Particle size 10 - 60 nm)
o Used in cosmetics, rubber filler, magnetic inks, building and construction, etc.

Brown Iron Oxide
Natural brown iron oxide:
o Brown: Naturally occurring oxide obtained from Maghemite (γ-Fe2O3).
o Obtained brown to bluish black colors
o Raw umber: Naturally occurring mixture of iron (Fe2O3), manganese oxide (MnO) and
aluminium silicate (Al2SiO5)
o Obtained color from deep brown black to cloudy coal black with yellowish undertone.
Synthetic brown iron oxide:
o Blend brown: Made by mixing of Yellow, Red and Black iron oxide
o Obtained color from bright to deep chocolate brown with reddish to yellowish undertone.
o Burnt umber: Heating or Calcination of raw umber
o Obtained color from deep brown to a rich black with reddish undertone.
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Brown Iron Oxide
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Physical Properties
Brown Iron Oxide Natural Synthetic
Pigment name Brown, Raw umber Blend brown, Burnt umber
Chemical Formula Fe2O3 , Fe2O3+MnO Fe2O3 , Fe2O3+MnO
Pigment Name Pigment brown 7 Pigment brown 6
Specific gravity 4.1 to 5 gm/cm3 4.3 to 5.2 gm/cm3
Particle Shape Cubical/Acicular Mixture / Acicular
Particle Size 0.7 to 2 µm 0.3 to 0.8 µm
Refractive index Brown-2.08 to 2.4, Raw umber-1.87 to 2.17 Blend brown- 2.3 to 2.5, Burnt umber-2.2 to 2.3
Mohs Hardness 5 to 6.5 5.5 to 6.5
Heat resistance 175⁰C 315⁰C

Manufacture: Brown Iron Oxide
o Process for Natural brown Iron oxide:
o Uses Maghemite (γ-Fe2O3) as ore.
o Due to strong magnetic properties it mostly not used for pigment.
o Process for Raw umber:
o Uses umber (Fe2O3 + MnO + Al2SiO5) as ore.
o Process for Synthetic Blend brown Iron oxide:
o Process for Synthetic Burnt umber:
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Yellow Iron Oxide Red Iron Oxide Black Iron Oxide Brown Iron Oxide
Raw umber Brown Iron Oxide
Calcination
300⁰C to 500 ⁰C
90⁰C

Surface Treatment: Brown Iron Oxide
48
o Surface treatment enhances pigment properties and controls particle
shape and particle size distribution
o Alumina(Al2O3), Aluminium hydroxide Al(OH)3 and Silica (SiO2)
o Enhances the dispersibility, heat stability and performance
properties of pigments
o Polysiloxane, Phenyl methyl polysiloxane.
Brown Oxide Core
Inorganic modifiers
Organic modifiers

Properties: Brown Iron Oxide
49
o Natural brown oxide and Raw umber have low tinting strength and less hiding.
o Synthetic raw umber have better tinting strength and hiding power.
o Pigment tone changed as per particle size change from larger to smaller.
o Raw umber has good light fast and chemical resistance but poor in heat resistance.
o Burnt umber has good light fast, chemical resistance and heat resistance
o Burnt umber used as a transparent pigments for furniture finishes color.
o Manganese ferrites(FeMn2O3) based brown iron oxide has better heat resistance (500⁰C)
o Used in Paint, stain, artist paint, cosmetic, construction etc.

2. Chromium Oxide Pigments
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Physical Properties
Chemical Formula Cr2O3
Pigment Name Pigment Green 17
o Known as chromium oxide green pigments, Chemical formula (Cr2O3).
o Obtained lighter to darker green with yellow to blue undertone at small to large particle size.
o Chrome green is blend of chrome yellow and iron blue pigment.

Chromium Oxide Pigments
51
o Excellent heat, chemical and solvent resistance, and has good light fastness & IR resistance.
o Manufacture by following two process:
o Reduction of alkali Dichromates:
o Reduction of Ammonium Dichromate:
Na2Cr2O7 + S Cr2O3 + Na2SO4
Na2Cr2O7 . 2 H2O + (NH4)2SO4 Cr2O3 + Na2SO4 +6H2O + N2
200⁰C
o Pigment use in paint, plastics, toys and cosmetics industry as per heavy materials limits and
their soluble fraction.
o As per EU classification its come under harmful substance (Xn) and substance is dangerous
for environment (N).

3. Mixed metal Oxide Pigments
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Mixed metal Oxide pigments
Pigment C.I Name Chemical Formula Crystal structure Color
Cobalt blue
Pigment blue 28 CoAl2O4
Spinel
Reddish blue
Pigment blue 36 Co(Al,Cr)2O4 Greenish blue
Cobalt green Pigment green 50 (Co,Ni,Zn)2TiO4 Inverse spinel Green
Zinc iron brown Pigment Yellow 119 ZnFe2O4 Spinel Light to medium brown
Spinel black
Pigment black 28 Cu(Cr, Mn)2O4
Spinel Black
Pigment black 22 Cu(Fe,Cr)2O4
o Better light & weather fastness, heat and chemical resistance.
o Use in Paint and color; as per EC guidelines not permitted for food, cosmetics and
pharmaceutical products.
o Mixed metal oxides with heavy metals are toxic, not recommended for paint and colors.

Bismuth Vanadate Pigments
o Naturally occurs in form of rare minerals clinobisvanite and dreyerite.
o These have monoclinic and tetragonal chemical structure
o Bright yellow color pigment with greenish undertone. Used in paint, plastics and cosmetics.
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Physical Properties
Chemical Formula BiVO4
Pigment Name Pigment Yellow 184
Particle Shape Platelet
Mohs Hardness 5 to 6

Manufacture: Bismuth Vanadate
o Synthetically manufacture by precipitation process.
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By using
Sodium Vanadate
[Bi(NO3)3 + HNO3] + [Na3VO4 + NaOH]  BiVO4 + 4NaNO3 + H2O
Bismuth
nitrate Bismuth
Vanadate
Sodium nitrate
Nitric acid
Sodium
vanadate
Caustic soda
+
pH - 7
10- 90⁰C
By using
Ammonium
Vanadate
[Bi(NO3)3 + HNO3] + [NH4VO3 + 3NH4OH]  BiVO4 + 4NH4NO3+ 2H2O
Bismuth
nitrate Bismuth
Vanadate
Ammonium
nitrate
Nitric acid
Ammonium
vanadate
Ammonium
hydroxide
+
pH - 7
10- 90⁰C

Surface Treatment: Bismuth Vanadate
56
o Surface treatment enhances pigment properties and controls particle shape
and particle size distribution
o Alumina(Al2O3), Calcium or Zinc phosphate and Silica (SiO2)
o Enhances the dispersibility, heat stability and performance properties
of pigments
o Amino alkyl alkoxy silane (3-aminopropyltriethoxysilane)
Bismuth Vanadate Core
Inorganic modifiers
Organic modifiers

Properties: Bismuth Vanadate
57
o High strength and brilliant color with greenish to reddish yellow undertone.
o Better gloss, light & weather fastness and hiding power (RI-2.45).
o Better solvent and migration resistance but weaker in chemical resistance (Color change in
acid media at pH <2).
o Application: 95% in Paint & automotive industry and 5% in plastic industry.
o Expensive inorganic pigments, due to relatively expensive raw material.

Cadmium Pigments
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o Obtained in Yellow, Orange and Red color with high durability.
o Cadmium Yellow: Occurs from Cadmium sulfide or mixture of Zinc and Cadmium sulfide.
o Cadmium Orange and Red: Occurs from Cadmium sulfoselenide, when sulfur is replaced by
selenium in the cadmium sulfide.
o Larger the selenium content, the color changes from yellow to orange, red and dark red.
o Better light and weather fastness, migration resistance and hiding power (RI- 2.5).
o Application: 90% in plastics and 10% ceramics (As per heavy materials limits and soluble
fraction).
o As per EU and NTP (US) classification its come under harmful substance – Carcinogenic (Xn)
and dangerous to environment (N).

Chromate Pigments
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o Chrome Yellow(PY34): Can be Pure or mixture of lead chromate & lead Sulfochromate.
o Molybdate Orange and Red (PR104): Mixture of lead molybdate with lead Sulfochromate.
o Colors depend on proportion of molybdate in the mixture.
o Chrome Green (PG15): Mixture of Chrome Yellow and Iron blue.
o Fast chrome green (PG48): Mixture of Chrome Yellow and Phthalocyanine blue & green.
o Better light and weather fastness, migration resistance and hiding power (RI- 2.65).
o Used in Paint and plastics industry (Within heavy materials limits and their soluble fraction).
o As per EU and GHS classification its come under harmful substance-Carcinogenic (Xn) and
dangerous to environment (N).

Ultramarine Pigments
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o Ultramarine is obtained by calcination of china clay, feldspar, anhydrous sodium carbonate,
sulfur & a reducing agent
o Reddish Blue (PB29): 75% of reaction product is blue pigment with other by products.
o Violet (PV15): Obtained by heating blue pigment with ammonium chloride at 240⁰C.
o Pink (PR259): Obtained by treating violet with hydrogen chloride gas at 140⁰ C.
o Excellent light fast and migration resistance but poor in chemical resistance
o Lower refractive index (1.5), thus poor hiding.
o Used in Paint, powder coating, plastics, rubber, cosmetics, etc.

Iron Blue Pigments
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o Two types of Pigment blue 27: Water insoluble (CI no: 77510) and soluble (77520)
o Obtained by aging and oxidization of hexacyanoferrate (HCF Prepared by precipitation of
Ferrous cyanides with ferrous salts in aqueous solution).
o Potassium, sodium and calcium HCF are used to manufacture iron blue.
o Have excellent light and weather fastness in mass tone but poor in tint tone.
o Very poor heat resistance, ignites in air at 140⁰C and has volatile content at 60 ⁰C.
o Better solvent resistance but poor in chemical resistance (Decomposes in concentrated acid)
o Mostly used in ink industry and very less in automotive finishes.
o Water soluble iron blue is used in paper industry to produce blue paper.

Black Pigments
64
o The most important black pigments are carbon black, iron oxide black and mixed metal oxide
black.
o Carbon black and soot are formed either by pyrolysis or by partial combustion of vapors
containing carbon.
o Carbon black is produced by burning oils, fats or resinous materials.
o The flame is cooled for carbon black deposition
o Iron Oxide and mixed metal iron oxide black are manufactured by using natural ore or
different iron salts by using synthetic process.

Carbon black Pigments
65
o Different grades of black are acetylene black, channel black, furnace black, lamp black and
thermal black; According to manufacturing process
o Carbon blacks are mostly used in rubber and paint industry
Physical Properties
Chemical Formula C
Pigment Name (PB 7 – Carbon, PB 6 – Lamp, PB 8 - Vine black)
Particle Size 13 to 95 nm
Refractive index Opaque

Manufacture: Carbon black
66
Carbon black manufacture process
Chemical Process Manufacturing Process
Currently
used
Raw material used
Incomplete
Combustion
Furnace black process 95% Petrochemical oil and coal tar oil
Degussa gas black process
5%
Coal tar Oil
Channel black process Natural gas
Lamp black process Petrochemical oil and coal tar oil
Thermal cracking
Thermal black process Natural gas
Acetylene black process Acetylene
For commercially available pigments, first two letters in the name stands for color strength and last one for the grade
For eg.: MCC – medium color channel black, HCF – high color furnace black
HC: high color, MC: medium color, RC: regular color, LC: low color
F: Furnace process, C: channel process.

Manufacture: Furnace Black
67
Feedstock:
o Petrochemical oil and coal tar oil are mostly used.
o Preheated oil and air are fed into the reactor in a controlled amount.
In the Reactor:
o Partial combustion, decomposition, particle formation takes place at 1200 to
1900⁰C temperature.
Quenching:
o Water is injected to stop the reaction by reducing temperature (500 to 800⁰C) of
carbon black smoke. Then smoke is sent to heat exchanger further cooling (250⁰C).
Separation:
o Fabric filter bags are used to separate carbon black and tail gas from smoke.
o Light and fluffy carbon black powder is removed from bag and collected in the tank.
Pellet formation:
o Carbon black is mixed with biding agent & water, and then dried in rotary drier.

Gas Black: Channel & Degussa
69
Channel black process:
o Uses natural gas as raw material.
o Uses H-shaped steel channel to produce pigment.
o Very less yield of channel black pigment (3-6%)
o Produces lot of waste and environmental pollutants.
o This process was stopped in US in 1976, due to low profit and environmental difficulties.
Degussa gas black process:
o Similar to channel black process but coal tar oil is used as raw material.
o Produces very less waste and pollutants
o Higher yield and better production rate than Channel black (up to 60%)
o Produces high quality pigment like channel black
o Mostly used in rubber, inks, plastics and coatings.

Manufacture: Gas Black
70
o Feed stock is partially vaporized and the vapor is transferred to production chamber along
with combustible carrier gas (Hydrogen, coke oven gas and methane)
o This mixture is aflamed by the many burners in a series.
o The burner flames are quenched by a cooling water rotating drum, where carbon black is
deposited and flue gas rises up as smoke
o Air is passed to the drums at regular intervals to control particle size of carbon black.
o This carbon black is scrapped and transferred using pneumatic conveyor.
o Carbon black is also separated from smoke using bag filters.

Manufacture: Lamp Black
72
o Feed stock (Petrochemical and coal tar oil) is burned in a flat steel vessel, to produce
carbon black containing smoke.
o The oil is continuously introduce in vessel to keep constant feed stock level.
o The off gas containing carbon black is shocked in to a conical exhaust pipe.
o The properties of carbon black depends on distance between vessel and exhaust and
amount of air sucked in to apparatus.
o The process is stopped at regular intervals to remove coke containing residue
o Produces coarse black (100nm), production rate 100 kg/h, this process very rarely used

Manufacture: Thermal Black
74
o Natural gas along with air is heated in a furnace as temperature reaches 1400⁰C, air is cut off
and natural gas undergoes pyrolysis.
o Due to this endothermic reaction, temperature falls to 900⁰C.
o Product is discharged (Carbon black & hydrogen gas) and a new heating period is started.
o Carbon black containing smoke are cooled using water and separated using bag filters.
o Fine thermal (FT) black is produced using natural gas diluted with hydrogen gas (120-200nm)
o Medium thermal (MT) black is produced using undiluted natural gas (300 – 500nm).
o Produces non-reinforcing carbon black, mostly used in rubber industry.

Manufacture: Acetylene Black
76
o Acetylene or acetylene containing gas (feedstock) is charged into a the preheated reactor.
o The decomposition heat evolved is maintained in the reactor to produce carbon black.
o Carbon black is collected at the bottom and transferred to a storage tank.
o Gives high yield (95-99%) with high rate of production 500 kg/h
o The application of Acetylene black is limited due to the high price.
o Mostly used in electric conductive agents, dry cell, colors, etc.

Forms of carbon black
78
o Very light and fluffy powder; original form.
o Pulverized to remove unwanted gases (NO2, CO, CO2, etc)
o Particle size 10 to 80 nm.
o Mostly used in coatings.
o Carbon black powder is rolled in rotating drums at 550 rpm to give
small spheroids.
o Pellet size 0.125 – 0.8 mm
Dry Pelletized black
o Mostly used in rubber industry.
o Carbon black, water and some amine based additives are mixed in
beading machine at 300 to 750 rpm then dried 150 – 250⁰C for 60 min.
o Pellet size 1-2 mm
Wet Pelletized black
Primary black

Surface Treatment: Carbon black
79
Carbon black surface treatment by two method
o Surface Oxidation:
o Pigment is heated with oxidizing agent at high temperature
o Surface obtains hydrophilicity due to oxygen containing groups
o Reaction is very unstable and hard to control
o Reaction with diazonium salts:
o Takes place at lower temperatures, the group carried by diazonium group is attached to
the pigment surface
o Hydrophilicity is achieved by more stable process

80
o Oxidizing Agents used:
o Air, Nitric acid, Nitrous acid, Sodium hypochlorite and Ozone.
o Oxygen containing group like ether, carboxyl, hydroxyl, ketone, phenol, etc. are attached
on surface of carbon black
o Treatment with diazonium salts:
o Aliphatic groups like poly acids, poly esters, poly glycols, etc. are attached to carbon
black surface directly.
o Similar groups are attached as aryl substitutions to the carbon surface.
o The Benzene ring holds the pigment surface and treatment group together like a hook.

81
Oxidation type surface treatment Surface treatment with diazonium salt

Properties: Carbon Black
82
o It has excellent heat resistance (1200⁰C) above that it transforms to graphite at 3000 ⁰ C.
o Good light absorption power (99.8%), including Infrared and ultraviolet light.
o pH of pigment depends on degree of oxidation, pH>7 (low oxygen content, basic surface
oxides), pH <6 (high oxygen content, acid surface oxides)
o Oxidation treatment enhances blackness and gives blue undertone.
o Mostly gas black is used in paint industry due to better dispersibility, non flocculation, gloss,
rheology, coloristic and weather resistance properties.

Black iron oxide / Carbon Black
83
Black Iron Oxide Carbon black
Found naturally or made synthetically Made by different process
Made using Iron containing components Made using Carbon containing components
Iron salt or ironic material used as raw material Carbon containing Oil and gas used as raw material
Large particle size(0.3 to 0.8 µm), weaker strength Small particle size(10 to 80 nm), Better strength
Less hiding than carbon black (RI-2.42) Better in hiding (Opaque)
Poor heat resistance (180⁰C) Better heat resistance (1200⁰C)
Higher mohs hardness ( 5.5 to 6.5) Lower mohs hardness ( 2.5 to 3.5)
Density is higher than Carbon black (4.6 to 5.3 gm/cm3 ) Density is lower than oxide black (1.8 to 2.1 gm/cm3 )
Brown or blue undertone Blue undertone

Specialty Pigments
85
o Five types pigments that produce special effect.
o Magnetic Pigments
o Anticorrosion pigments
o Luster Pigments
o Transparent Pigments
o Luminescent pigments

Magnetic Pigments
86
o Five types magnetic pigment available:
o Iron oxide pigments
o Cobalt containing iron oxide pigments
o Chromium dioxide pigments
o Metallic iron pigments
o Barium ferrite pigments
o used in magnetic information storage system such as audio and video cassettes, floppy disk,
hard disk, high density recording media, computer tapes, etc.

Anticorrosion Pigments
87
o Phosphate pigments: Zinc, Aluminum, Chromium, metal and multiphase Phosphate.
o Other Phosphate containing Pigments: Iron Phosphide, Zinc hydroxyphosphite.
o Borosilicate Pigments
o Borate Pigments
o Chromate pigments: Zinc containing, Strontium chromate, Lead silicochromate.
o Molybdate Pigments
o Lead and Zinc Cyanamides
o Ion Exchange Pigments
o Metal Oxide Pigments: Red Lead, Calcium Plumbate, Zinc and calcium ferrites, Zinc Oxide.
o Powdered metal Pigments: Zinc dust, Lead powder.
o Flake Pigments
o Organic Pigments

Luster Pigments
89
o Four types Luster pigment available:
o Nacreous and Interference Pigments
o Natural Pearl Essence
o Basic lead carbonate
o Bismuth Oxychloride
o Metal oxide – Mica pigments
o Metal effect Pigments
o Consist flake of aluminum, copper & copper – zinc alloys and Zinc.
o Used in colorants to achieve additional properties like color depth, brilliance, iridescence,
color shift (flop), metallic effect and other spectacular effects.

Transparent Pigments
90
o Five types Transparent pigment available:
o Transparent Iron oxide
o Transparent Iron blue
o Transparent Cobalt blue and green
o Transparent Titanium dioxide
o Transparent Zinc oxide
o Used in Cosmetics, plastic & polyethylene industry and paints as transparent UV-light
shielding chemical.

Luminescent Pigments
91
o Four types Luminescent pigment available:
o Luminescence of crystalline Inorganic Phosphors
o Sulfides and selenides
o Oxysulfides
o Oxygen dominant phosphors
o Halide Phosphors
o Used in lighting, X-ray technology, Cathode ray tubes and Product coding industries.

Inorganic pigments

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