Arihant Metallica

Boisar, Thane, Maharashtra

Calcium being an auxiliary drier, has little drying action in itself but is very useful in combination with active driers like Cobalt & Lead Octoate. In vehicles that show poor tolerance for lead, calcium can replace part of the lead with a larger amount of calcium to prevent the precipitation of the lead & maintain drying efficiency. Calcium is often used to replace lead where toxicity of lead must be avoided. Calcium is also useful as pigment wetting & dispersing agents & help to improve hardness & gloss & reduce “Silkinsâ€. When ground with drier adsorbing pigments, calcium minimizes loss of dry by being preferentially absorbed.

Zirconium is a most useful & efficient auxiliary drier. Zirconium like lead serves as a through drier & is generally used in combination with Cobalt, Manganese & Calcium. Unlike Lead, Zirconium is a poor pigment wetting & dispersing agent.

Zirconium is an active cross-linking agent & as such improves hardness of stoved films as well as their adhesions.

Zirconium is not as effective in phenolic resin based media it is recommended as a catalyst for epoxy esters. Use of Lead driers in combination with Zirconium is to be avoided totally.

Lead is a through drier & is always used as active or top drier. It promotes hard & through drying throughout the film. When lead is used with cobalt or Calcium Octoate it is advisable to add Calcium Octoate first to eliminate possibility of Lead Octoate to react with unreacted pthalic anhydride of alkyd resin, which could form Lead Pthalate. In exterior paints & floor finishes Lead is used along with Manganese to produce tough & hard film. It is also used in Polyurethane finishes as auxiliary drier. Lead drier improves the drying time of double boiled linseed oil.

Lead in combination with cobalt & calcium are suggested, particularly for long oil alkyds lead is the most important drier. However some of the problems connected with lead driers such as sulfur staining & reaction with polybasic acids are overcome by inclusion of calcium drier. As lead is toxic in nature its usage toys & edible film packaging is to be avoided.

Manganese driers are intermediate in activity & they have both oxidizing & polymerizing properties. It used alone in backing finishes & along with Cobalt & Lead in air drying applications. When used in combination with Lead, hard tough & durable films are produced. It is mainly used for exterior paints, floor finishes, backing enamels, foundry chemicals etc. the dosage of Cobalt Octoate can be minimized by using Manganese Octoate as it is capable of replacing Cobalt because of its high activity.

One disadvantage in use of manganese driers is their relative dark color, which has a tendency to discolor white or light finishes.

It is an extremely active & most widely used drier in coatings & capable of being used even as a single Drier. It is primarily an oxidation catalyst & acts as a “Surface Drierâ€. It may have a tendency to cause surface wrinkling, hence to provide uniform drying, it is generally used in combination with other auxiliary driers. It is generally added at 0.05 to 0.5% depending on the vehicle solids. Cobalt drier prevents atmospheric humidity to enter into paint films due to its unique property. This will help to increase gloss & reduces brittleness of the film. This drier is a universal drier, which is essential in all media.

As quantity of Cobalt Drier used is very small, it minimizes discoloration in paints & enamels as compared with other Driers. Cobalt does not discolor white paints as the deep blue color of the cobalt counteracts the yellow of the oils & resins & thereby enhances the whiteness of the paint. Cobalt is an effective accelerator for catalytic action of MEKP to polymerize unsaturated polyester resin.

Barium can be used in place of lead and calcium. It does not give haze like lead in alkyds. It is mainly used in P.V. C. as heat and light stabilizer with cadmium.

Applications

• Used as a catalyst in rubber manufacturing
• Used as catalyst in top-grade printing ink
• Available for coating grinding dispersant, ultraviolet light absorbent, etc.