Coil coating system

Roll and coil coating systems utilize liquid coating materials with organic solvents, which must be stored, manifested, and disposed of according to 40 CFR Part 262 if classified as hazardous waste under 40 CFR Part 261. 

The use of roll and coil coating systems leads to pollution prevention over traditional spray application systems due to their higher transfer efficiency (>95%) and lower volatilization of organic solvents. 

Bismuth vanadate pigments are used in the manufacture of lead-free, weather resistant, brilliant yellow colors for automobile finishes and industrial paints. They are suitable for the pigmentation of solvent-containing paints, water-based paints, powder coatings, and coil-coating systems. It can be mixed with other pigments... 

Fig. 37 Schematic cross section of typical paint systems for steel and galvanized steel (a) automotive coating system including an ED-paint and (b) a coil-coating system for the building industry including a roll-coated paint as corrosion-resistant primer.

Long life and excellent weathering characteristics are required for the main application of coil coatings (architectural cladding). This means that new coil-coating systems have to be fully proved before they are widely adopted. 

Figure 7-68. Examples of technical coil coating systems based on galvanized steel, (a) Fast delamination (b) extremely slow delamination. The samples had been exposed before to 3% NaCl at 40°C for times as indicated (Altgassen, 1996).

Figure 7-69 shows potential profiles of a coil-coating system on galvanized steel for defects only prepared down to a) zinc and... 

Patented modem coil coating system uses infrared radiation in ciuing oven with near infrared emitters and oxidizing chamber for destmction of volatile solvents. ... 

Chem. Descrip. Blend of modified acrylic polymer with hydrocarbons silicone-free Uses Deaerator and leveling agent for coil coating systems Properties Colorless cl. vise, liq. dens. 1.02 g/ml (20 C) flash pt. > 100 C 80% solids... 

Uses Smoothness and leveling agent for aq. systems rec. for water-thinnable varnishes, coil coating systems... 

P.V.D.F. Polyvinylidene fluoride (p.v.d.f. or p.v.f.2) dispersions are applied by the coil-coating process. They are blends of p.v.d.f. resin and acrylic. The combination produces a system which has excellent weather-ability and which can be bonded via an adhesive primer to a galvanised steel or aluminium substrate. 

Granular bed filters are used in ten coil coating plants to remove residual solids from the clarifier effluent, and are considered to be tertiary or advanced wastewater treatment. Chemicals may be added upstream to enhance the solids removal. Pressure filtration is also used in this industry to reduce the solids concentration in clarifier effluent and to remove excess water from the clarifier sludge. Figure 7.4 shows a granular bed filter and Table 7.13 presents the heavy metal removal data of a lime clarification and filtration system. 

Hamilton Standard of the U.S. EPA has reported several coil coating plants wastewater treatment case histories.8,9 A full-scale wastewater treatment plant system has performed well for treatment of the wastewater generated from coil coating steel subcategory operations. The process principles and operational data of the full-scale treatment of a steel subcategory wastewater are summarized herein for the convenience of readers ... 

Another specialty area is coil coating, which involves coating metal coils by continuous operation. Modern roller systems afford speeds of up to 200 m/min. Most coils are made of cold-rolled and surface treated steel, aluminum, or alloys of the latter with manganese or magnesium. Coating systems are based on alkyd or acrylic resins, oil-free polyester, silicone-modified polyester or acrylic resin, poly(vinylidene fluoride), or poly(vinyl fluoride). Water-reducible systems, mainly based on acrylic resins, have been developed for aluminum as well as for steel coils [21-24], Drying is carried out by continuous operation in gas- or oil-heated multichamber ovens. 

The plastics industry uses P.Y.173 to color various polymers. Incorporated in plasticized PVC, P.Y.173 is one of the tinctorially weaker pigments of its class. 1.8% pigment is required to produce 1/3 SD specimens containing 5% TiOz. The systems are almost completely fast to overcoating. P.Y.173 demonstrates excellent lightfastness and durability in rigid PVC and in PVC plastisols intended for coil coating. 

Inhibitive Primers. The traditional primers are red lead and linseed oil, alkyd resins and zinc potassium chromate, proprietary epoxy, alkyd, urethane and latex systems with modified phosphate, borate and molybdate pigments. Chromate-based pigments, although in use in aircraft coatings, automotive primers and coil coating primers, are subject to environmental concern on the toxicity of hexavalent chromium which is likely to result in their replacement by innocuous products. 

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