Paint Driers

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 “Silkins”. When ground with drier adsorbing pigments, calcium minimizes loss of dry by being preferentially absorbed.

Cerium (Rare earth) is a primary drier, promotes polymerization and imparts through drying property. In alkyd based varnishes Cerium is more active as compared to lead. In contrast with lead driers, Cerium does not cause turbidity in oils and alkydbased varnishes.

It has a synergistic effect when used in combination with Cobalt resulting in the need for using a lower percentage of Cobalt and thereby offering an economy. In airdrying white colourless or clear or pastel shades care must be taken to predetermine the quantity required to obtain satisfactory drying in order to avoid yellowing. As a replacement to lead, Cerium finds use in lead-free composition and where sulphur containing pigments are used. It also resists atmospheric hydrogen sulphide stain.

Copper is an anti fouling agent. It is used in ship bottoms paints. Copper Octoate Hydrolyses gradually in to Copper Hydroxide & Octoic Acid in the presence of seawater, Copper Hydroxide is an active toxicant.

It is used as a rot proofing agent in textiles, cordage etc. & to prevent dry rot & mildew growth in timber. Its insecticidal properly is taken advantage of to import a long lasting protection against termites, beette & ambrosia & many other insects attacking timber/lumber, Copper may be applied on textile fabrics by dipping, spraying or impregnation. The recommended dosage is 2% to 2.5% as metal.

Iron Octoate is used in backing finishes, since it promotes rapid drying by polymerization. It is an excellent wetting agent for carbon black & iron oxide. It prevents adsorption of driers on the surface of the pigments & increases gloss. In airdry finishes it is useful in eliminating film tackiness of paints containing a high percentage of non-drying oil component such as fish oil.

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.

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.

Miscible with organic solvents and oils. Suitable to use with other siccatives. Used for Polyester and Isocyanurate foam initiator. Potassium Octoate is used in conjunction with Cobalt for a synergistic effect and to reduce discoloration of the final Gel-Coat. Potassium may offer cost savings as well as a decline in gel-time drift.

Strontium Octoate is replacement of Lead Octoate, where Lead free Paint/Ink is required. It improves through drying in adverse effect like high humidity & low temperatures.

Zinc being an auxiliary drier, used in conjunction with redox metals. The primary function of zinc is to keep the film “Open” by retarding Surface dry, thus permitting hardening through out & preventing surface wrinkling, particularly in Cobalt containing films & enamels.

Zinc is a powerful wetting & dispersing agent, & when incorporated early in formulation, it greatly reduces the time of mixing & grinding. Because of the extremely light colour, Zinc can be added without discoloring the film.

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.