Cobalt driers

Cobalt. Without a doubt cobalt 2-ethyIhexanoate [136-52-7] is the most important and most widely used drying metal soap. Cobalt is primarily an oxidation catalyst and as such acts as a surface or top drier. Cobalt is a transition metal which can exist in two valence states. Although it has a red-violet color, when used at the proper concentration it contributes very Httie color to clear varnishes or white pigmented systems. Used alone, it may have a tendency to cause surface wrinkling therefore, to provide uniform drying, cobalt is generally used in combination with other metals, such as manganese, zirconium, lead, calcium, and combinations of these metals. 

PrtparaHon of imprcvited dr% r. If the commercial driers (cobalt and lead) specified under MiUmol and Equipment above are not available, the following improvised driers can be made using either flashlight batteries or powdered lead oxide CPbjOt). These improvised driers are used in the same manner as the commercial driers. 

Chem. Descrip. Calcium drier Uses Drier in org. coatings, inks, polyesters Properties Gardner 5 max. sp.gr. 0.950-1.010 dens. 7.91-8.42 Ib/gal vise. (Gardner) B max. flash pt. 104 F (PMCC) 10.0 0.1% metal Troymax Drier Cobalt 6% [Troy]... 

In stoving paints it is usually satisfactory to include low levels (0.01-0.05% metal on binder) of a single primary drier. Cobalt, manganese, cerium and iron (which only acts as a drier at higher temperatures) are used. Unacceptable discoloration in pale colours can be a hazard, particularly with iron and cerium. 

Driers. These are generally soaps of cobalt, manganese, and other metals formed with organic acids such as linoleic, naphthenic, and other organic acids. They catalyze oxidation of drying oils (qv), and thus are used in inks that dry by oxidation (see Driers and metallic soaps). 

Air oxidation of dyestuff waste streams has been accompHshed using cobalt phthalocyanine sulfonate catalysts (176). Aluminum has been colored with copper phthalocyanine sulfonate (177,178). Iron phthalocyanine can be used as a drier in wood oil and linseed oil paints (179). 

Vehicles. The soHd pigments are dispersed iato the ink vehicle, which consists of a combination of resia, oil, and solvent. The solvent is absorbed by the paper, leaving a partially dry ink film of resia and oil that biads the pigment to the paper. This film then hardens by oxidation. Oxidation of the vehicle is aided by varnish driers, ie, metallic salts. Cobalt driers are considered the most effective (see Driers and metallic soaps). 

Cobalt. There is no U.S. mine production of cobalt. Refining of imported nickel—cobalt mattes has not occurred since the mid-1980s. About 1600 t of secondary cobalt was recycled from scrap by 13 faciUties in the United States representing - 22% of total U.S. consumption. The price of the metal was around 44/kg. Most is imported from Zaire and Zambia. Increasing quantities are coming from Russia. Historically, the price of cobalt has been quite volatile and dependent on the pohtical environment in those countries. Cobalt is used in superaHoys, 40% catalysts, 14% paint driers, 11% magnetic alloys, 10% and cemented carbides and other uses, 16%. 

Zirconium tetrafluoride [7783-64-4] is used in some fluoride-based glasses. These glasses are the first chemically and mechanically stable bulk glasses to have continuous high transparency from the near uv to the mid-k (0.3—6 -lm) (117—118). Zirconium oxide and tetrachloride have use as catalysts (119), and zirconium sulfate is used in preparing a nickel catalyst for the hydrogenation of vegetable oil. Zirconium 2-ethyIhexanoate [22464-99-9] is used with cobalt driers to replace lead compounds as driers in oil-based and alkyd paints (see Driers and metallic soaps). 

Branched-chain acids have a wide variety of industrial uses as paint driers (7), vinyl stabilizers (8), and cosmetic products (9). Cobalt and manganese salts of 2-ethyIhexanoic acid and neodecanoic acid are used as driers for paint, varnishes, and enamels litbium, magnesium, calcium, and aluminum salts of 2-ethyIhexanoic acid are used in the formation of greases and lubricants (see Driers and metallic soaps). Derivatives of isostearic acid have been used as pour point depressants in two-cycle engine oils, as textile lubricants, and in cosmetic formulations. Further industrial appHcations can be found (10). 

The metal salts of neodecanoic acid have found wide usage as driers for paints and inks (95,96). Metal neodecanoates that are used include silver (80), cobalt (82), and zirconium (79), along with lead, copper, manganese, and 2inc (see Driers and metallic soaps). 

Cobalt in Driers for Paints, Inks, and Varnishes. The cobalt soaps, eg, the oleate, naphthenate, resinate, Hnoleate, ethyUiexanoate, synthetic tertiary neodecanoate, and tall oils, are used to accelerate the natural drying process of unsaturated oils such as linseed oil and soybean oil. These oils are esters of unsaturated fatty acids and contain acids such as oleic, linoleic, and eleostearic. On exposure to air for several days a film of the acids convert from Hquid to soHd form by oxidative polymeri2ation. The incorporation of oil-soluble cobalt salts effects this drying process in hours instead of days. Soaps of manganese, lead, cerium, and vanadium are also used as driers, but none are as effective as cobalt (see Drying). 

Eor water-based alkyd paints, greater (0.2% cobalt on a resin basis) concentrations of drier are required than for other systems because the reaction of the drier with water decreases the activity of the catalyst. The cobalt content of oil-based paint formulations is usually 0.01—0.05% cobalt. Although the concentration of cobalt in the formulations is small, the large volume of paints, inks, and varnishes constitute a significant use for cobalt chemicals. 

A.ctive driers promote oxygen uptake, peroxide formation, and peroxide decomposition. At an elevated temperature several other metals display this catalytic activity but are ineffective at ambient temperature. Active driers include cobalt, manganese, iron, cerium, vanadium, and lead. 

Naphthenates of cobalt, manganese, calcium, copper, iron, zinc, and zirconium are used as driers in printing inks. Their use in coatings is declining as a result of the use of higher metal content synthetic driers and the overall trend to latex paint in architectural coatings. 

Metal Linoleates and Resinates. The calcium and cobalt salts of Hnoleates and resinates are used chiefly as components of metallic driers used in printing inks. Copper Hnoleate [7721-15-5] is used in antifouling paints for marine use (4). 

Studies by and nmr of the reactions of ethyl Hnoleate with oxygen ia the presence of cobalt driers iadicate that the cross-linking reactions... 

The net result is formation of water and a high concentration of free radicals. The cobalt cycles between the two oxidation states. Lead and 2irconium salts cataly2e drying throughout the film and are called through driers. Calcium salts show Httle, if any, activity alone, but may reduce the amount of other driers needed. 

Similar reactions also occur with organic peroxides, dioximes, paint driers such as cobalt naphthenate and furfural. It is interesting to note that the cure time is dependent on the humidity of the atmosphere. With lead peroxide the rate doubles by increasing the relative humidity from 40 to 70%. The most important... 

In the United States softer stocks have been employed using a drying oil which is incorporated with a drier such as cobalt naphthenate to harden the oil. 

Kobalt-rosa, n. cobalt red. -salz, n. cobalt salt, -spat, m. (Afm.) aphaerocobaltite. -speise, /. cobalt speias. -trockner, m. cobalt drier, -verbindung, /. cobalt compound, -vitriol,... 

A paint rarely consists solely of pigment dispersed in a solution of a binder. For one reason or another, small quantities of ancillary materials called additives are included. The oldest and still the most important are the driers which are used in all air-drying and many stoving paints containing drying oils. They are organic salts of certain metals, notably cobalt, calcium, barium, zirconium and manganese, with lead very much in decline. 

Are used to accelerate autoxidation and hardening of oxidisable coatings. Metal soaps, used as paint driers, can be made from a variety of carboxylic acids, including the commercially important naphthenic and 2-ethyl hexanoic acids, tall oil, fatty acids, neodecanoic and isononanoic acid. Cobalt is unquestionably the most active drier metal available. Metallic driers such as cobalt naphthenate or octoate and zinc salts can interact with UVAs, HALS, or AOs. 

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