Driers, coatings

Uses Drier for paints, in food-contact coatings drier migrating from food pkg. 

Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes Uses Drier for paint, varnish, in food-contact coatings drier migrating from food pkg. adhesion promoter bonding rubber to steel and other metals catalyst accelerator in unsat. polyester resins accelerator in food-contact crosslinked polyesters Regulatory FDA 21CFR 175.300, 177.2420, 181.25... 

Precaution Combustible Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes Uses Drier for paints, in food-contact coatings drier migrating from food pkg. 

These overtone stains are normally composed of pigments, oils, solvents, and driers. The important quaHty of glazes and wiping stains is the abiHty to apply a color coat which can be wiped on and then highlighted to add depth and contrast to the overaU appearance of the finish. 

Iron. This is a specialty drier that is considered active at temperatures of about 130°C. For this reason iron 2-ethyIhexanoate [19583-54-1] is used in bake coatings that require maximum hardness. The principal drawback of using iron driers is that iron contributes a characteristic brownish red color to the coating and should only be used in dark pigmented systems. It has been reported that iron aids the dispersion of carbon black pigment and reduces the tendency for orange peel film defects (6). 

Cerium/Rare Earth. Cerium 2-ethyIhexanoate [56797-01-4] and rare-earth driers promote polymerization and through dry. Like iron they are active at elevated temperature and, since they do not contribute to film discoloration, are recommended for white bake finishes and overprint varnishes where color is critical. Rare earths also find use at the other end of the temperature spectmm in coatings dried at low temperature and high humidity. 

Because of the toxicity associated with lead compounds, governmental rulings have severely limited the use of lead drier in coatings. From a performance viewpoint the use of lead in aluminum paint will destroy the leafing characteristics of the film. Coatings containing lead that are exposed to sulfur fumes will discolor. 

Bismuth. Bismuth 2-ethyIhexanoate [72877-97-5] is an auxiliary drier that has been promoted for drying under adverse conditions. Like rare earths, in some coatings it is reported to give better results than zirconium at low temperature and high humidity. 

Loss of Dry. When the initial dry time of a solvent-based coating becomes substantially longer after aging, it is said to lose dry. The primary cause of this problem has been identified as adsorption of the drier on the pigment surface. Pigments with large surface areas are the worst offenders. 

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. 

W. S. Stewart, in W. H. Madison, ed.. Paint Driers andEidditives, Federation Series of Coatings Technology Federation of Societies for Paint Technology, Philadelphia, Pa., 1969, Unit 11, pp. 1—26. 

In modem manufacturing methods the oil is sometimes reacted directly with the glycerol to form a monoglyceride and this is then reacted with the acid to form the alkyd resin. When the resulting surface coating is applied to the substrate the molecules are substantially linear. However, in the presence of certain driers such as lead soaps there is oxidative cross-linking via the unsaturated group in the side chain and the resin hardens. 

We will cover a simple drying model to examine the radiation drier of coated paper. We assume there are no major temperature or humidity variations in the direction of the paper web thickness, and that temperature T and humidity u are constant in the direction of thickness. This assumption requires that the capillary action be ignored, and the pressure gradient of water is zero on the assumption hu/dx = dT/dx = 0. How is it possible that the humidity distribution remains uniform ... 

The velocity of a coated paper web is 17 m s and the width of the IR drier is 0.4 m. Thus the delay time in one drier is 0.4/17 = 0.0235 s. This yields an indication of the processes inside the drier, using the above calculated values ... 

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. 

Liquid and solids Coating Spray drier, fluidized bed coater... 

Hanni et al. (1976) described a continuous fluidized bed drier using the centrifugal principle. It consisted of a perforated horizontal cylinder rotating inside a plenum with hot air blown across the outside of the cylinder and perpendicular to the axis of rotation (Figure 1.20). Vanes placed in the air inlet allowed the incident angle of the air flow to be varied from 0° to 45° to the perpendicular. Particles were fluidized inside the Teflon-coated stainless steel cylinder which could be tilted by up to 6° in order to control particle residence time. The cylinder, of... 

This is a very broad class of compounds commonly used in coatings. Over 400-500 different alkyd resins are commercially available. They are polyesters containing unsaturation that can be cross-linked in the presence of an initiator known traditionally as a drier. A common example is the alkyd formed from phthalic anhydride and a glyceride of linolenic acid obtained from various plants. Cross-linking of the multiple bonds in the long unsaturated chain R produces the thermoset polymer by linking R groups of separate molecules with each other. 

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