What are the raw materials for making white pigment?

What are the raw materials for making white pigment?

As a seasoned supplier of white pigments, I've witnessed firsthand the intricate world of pigment production and the crucial role that raw materials play. The journey to creating high - quality white pigments is a blend of science, art, and the right choice of starting materials. In this blog, I'll delve into the primary raw materials used in making white pigments, their properties, and how they contribute to the final product.

Titanium Dioxide (TiO₂)

Titanium dioxide is by far the most widely used raw material for white pigments. It has several outstanding properties that make it a top choice in the industry.

Properties

• High refractive index: Titanium dioxide has a very high refractive index, which means it can scatter light effectively. This property gives white pigments made from TiO₂ their excellent hiding power. When applied as a coating, it can cover the underlying surface completely, making it ideal for paints, coatings, and plastics.
• Chemical stability: It is highly resistant to chemical reactions, which ensures the longevity of the pigment. Whether it's exposed to acidic or alkaline environments, TiO₂ - based white pigments maintain their color and integrity over time.
• UV resistance: Titanium dioxide can absorb and scatter ultraviolet (UV) light. This is crucial in applications such as outdoor paints and plastics, as it helps protect the underlying material from UV - induced degradation, such as fading and cracking.

Production

There are two main methods of producing titanium dioxide: the sulfate process and the chloride process. The sulfate process involves reacting ilmenite (a titanium - iron ore) with sulfuric acid, followed by a series of purification and calcination steps. The chloride process, on the other hand, uses rutile or synthetic rutile as the raw material and reacts it with chlorine gas at high temperatures. The chloride process generally produces a higher - quality product with better particle size control.

Zinc Oxide (ZnO)

Zinc oxide is another important raw material for white pigments.

Properties

• Antibacterial and antifungal properties: In addition to its white color, zinc oxide has natural antibacterial and antifungal characteristics. This makes it a popular choice in applications such as paints for hospitals, schools, and other public buildings where hygiene is a concern.
• Good heat resistance: It can withstand relatively high temperatures without significant degradation. This property is useful in high - temperature applications, such as in some industrial coatings and plastics that may be exposed to heat during processing or use.
• UV absorption: Similar to titanium dioxide, zinc oxide can absorb UV light. It is often used in sunscreens and other UV - protecting products, as well as in outdoor coatings to enhance their UV resistance.

Production

Zinc oxide can be produced through several methods, including the indirect process (French process) and the direct process. The indirect process involves heating zinc metal to vaporize it, and then oxidizing the zinc vapor in air. The direct process uses zinc ores, such as zinc carbonate or zinc sulfide, which are roasted to produce zinc oxide.

Zinc Sulfide (ZnS)

Zinc sulfide is also a significant raw material for white pigments, especially in certain specialized applications.

Properties

• Good dispersion: Zinc sulfide particles can disperse well in various media, such as polymers and solvents. This property ensures a uniform distribution of the pigment in the final product, resulting in a consistent color and appearance.
• Low toxicity: It is relatively non - toxic, making it suitable for use in applications where human contact is likely, such as in some food packaging materials and children's toys.
• Luminescence properties: Some forms of zinc sulfide exhibit luminescence, which can be useful in applications such as glow - in - the - dark products.

Production

Zinc sulfide is typically produced by reacting zinc salts, such as zinc sulfate, with a sulfide source, such as hydrogen sulfide or sodium sulfide. The reaction results in the precipitation of zinc sulfide, which can then be further processed and purified. For high - quality applications, such as Engineering Plastic Zinc Sulfide, additional steps may be taken to control the particle size and surface properties of the zinc sulfide.

Calcium Carbonate (CaCO₃)

Calcium carbonate is a common and cost - effective raw material for white pigments.

Properties

• Low cost: It is abundant and relatively inexpensive to obtain, which makes it an attractive option for applications where cost is a major consideration.
• Good whiteness: Calcium carbonate has a high degree of whiteness, which can contribute to the overall brightness of the white pigment.
• Good filler properties: It can act as a filler in addition to being a pigment. In paints, plastics, and rubber, calcium carbonate can improve the mechanical properties of the final product, such as hardness and stiffness.

Production

Calcium carbonate can be obtained from natural sources, such as limestone, marble, and chalk. It can also be produced synthetically through a precipitation process, where calcium hydroxide reacts with carbon dioxide. The synthetic calcium carbonate often has better particle size control and purity compared to the natural sources.

Barium Sulfate (BaSO₄)

Barium sulfate is used in some high - end white pigment applications.

Properties

• High density: Its high density gives it good settling properties, which can be useful in some coating applications to prevent the pigment from floating or separating.
• Chemical inertness: Barium sulfate is highly chemically inert, which means it is resistant to most chemical reactions. This property makes it suitable for use in harsh chemical environments.
• Good gloss and smoothness: In coatings, barium sulfate can contribute to a high - gloss and smooth finish, enhancing the aesthetic appeal of the final product.

Production

Barium sulfate can be mined from natural barite deposits. It can also be produced synthetically by reacting barium salts, such as barium chloride, with a sulfate source, such as sodium sulfate. The synthetic barium sulfate can be tailored to have specific particle sizes and surface properties for different applications.

Conclusion

The choice of raw materials for making white pigments depends on a variety of factors, including the desired properties of the final product, cost, and the specific application. Titanium dioxide is the dominant raw material due to its excellent hiding power and other properties, but zinc oxide, zinc sulfide, calcium carbonate, and barium sulfate also play important roles in different niches.

As a white pigment supplier, I understand the importance of providing high - quality products that meet the diverse needs of our customers. Whether you're in the paint, plastics, coatings, or other industries, we have the expertise and resources to offer you the right white pigment solutions. If you're interested in learning more about our white pigments or are looking to start a procurement discussion, I encourage you to reach out. Our team is ready to assist you in finding the best raw material - based white pigments for your specific requirements.

References

• Lewis, R. J. Sr. (Ed.). (2004). Hawley's Condensed Chemical Dictionary. John Wiley & Sons.
• Kirk - Othmer Encyclopedia of Chemical Technology. (2005). John Wiley & Sons.
• Pigment Handbook, Volumes 1 - 3. (1973 - 1978). John Wiley & Sons.