Solventborne coatings

Silicones are also the predominant defoamer components in solventborne coatings. Products with a correct balance of compatibility and incompatibility can be synthesized by selectively modifying the silicone backbone with polyether and/or alkyl chains. 

Isocyanates also react with water if this happens in a solventborne coating during application, CO2 is generated, which may reduce gloss or result in... 

The procedures specified by the US EPA for testing paint products for compliance with VOC limits are described in Federal Reference Method 24, which employs several ASTM test standards. VOC values for waterborne or solventborne coatings are calculated by the following formula ... 

A wide range of rheology modifier additives is commercially available for solventborne coatings. Some important classes are discussed in the following chapters. 

The final part of the picture concerns recyclability of coating materials. Improvements in transfer efficiency to substrate and recycle and reuse of overspray are becoming of increasing importance. The use of super critical CO2 processing and application is being commercialised and is seen to offer potential benefits over conventional solventborne technologies. 

Flow Coat Conversion. Solventborne flow coaters are a major source of hydrocarbon emissions. This source became an early target for a replacement system. An alternative to reduce emission was the gas incinerator, but high capital costs and gas consumption precluded its use. 

Further, the dislocations in the world oil supply and the resultant discontinuities in petrochemical prices increased the cost of traditional low-solids solventborne systems and the cost of curing higher temperature thermosetting systems as well. The coatings industry responded to these pressures with new technology low-emission coatings. 

Automotive Finishes. Important industrial automotive topcoats are produced from alkyd resins. Two-coat metallic finishes consist of an acrylic clearcoat and a metallic basecoat. Solventborne basecoats are generally composed of cellulose acetobutyrate and a low molecular mass, branched polyester resin which exhibits high reactivity with precondensed melamine cross-linking resins. 

Environmental Protection. On account of the high paint transfer efficiency and low solvent content, environmental pollution in electrodeposition coating is much lower than with spray coating. The solvent contents of electrodeposition paints relative to the solids content are 5-10% in comparison with solventborne spray paints with a solvent content of 50-100%. The most important sources of emission are the electrodeposition tank, the rinsing zone, the stoving oven, and the drain of the ultrafiltrate [3.125]. Developments in new electrodeposition paints aim to reduce the organic volatile solvent content, to have fewer condensation products in the stoving ovens, and to have lead-free formulations [3.126]. 

Wheels are electrocoated engine blocks are coated with heat-resistant, usually waterborne materials. Other parts (e.g., steering equipment and shock absorbers) are painted with two-pack, one-coat epoxy systems that are usually solventborne use of waterborne systems is, however, increasing. 

Field trials have shown that the expected durability of the new waterborne coating systems is equal to that of conventional solventborne paints. As a further advantage, the number of single coats can be reduced from three to two. Standard freight cars are painted with a three-coat alkyd system consisting of an anticorrosive primer, an intermediate coat, and a topcoat, total DFT is ca. 150 pm. Such systems are being replaced by single-coat systems of waterborne acrylic resins and acrylic copolymers to reduce solvent emission. 

Solventborne paints are based on synthetic resins (e.g., acrylate styrene copolymers) which are soluble in aliphatic and/or aromatic hydrocarbons. The properties of these coatings are chiefly determined by the nature and proportion of the monomers. 

The need for waste air treatment can generally be avoided by replacing conventional, high-solvent paints by low-solvent coatings. In some cases smaller waste air treatment plants may be necessary for specific demarcated areas where, for example, a solventborne layer is applied. 

However, the poor adhesion of the surface does not allow a further painting stage. The surface of Parylene coatings can be modified by a special plasma coating. In this way, an interlayer is placed to provide good adhesion to the substrate as well as to a subsequent primer. After this procedure, the hydrophobic Parylene polymer again becomes paintable with both solventborne and waterborne spray primers." ... 

Decorative paints, so called because they form a decorative coating inside and outside buildings, represent over 50% of coatings consumption in both the USA and Europe. This market can be further divided into trade and retail sectors. The former supplies the professional painter while the latter serves the retail outlets. One of the most noticeable developments in the retail sector in recent years has been the increase in paint sales from the large DIY stores at the expense of the smaller suppliers. Both retail and trade sectors can be further divided into waterborne emulsion paints , for walls, ceilings, etc., and solventborne gloss, primer, varnish, etc. 

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