Paints and varnishes

Most black pigments are made of carbon black formed by depositing carbon from a smoky flame of natural gas on a metal surface. Lampblack is made similarly by burning oik Bone blacks are made from charred bones. Graphite occurs naturally or can be prepared from coal in electric furnaces. Mineral blacks come from shale, peat, and coal dust. Iron oxide blacks are found in nature or prepared. Blue lead sulfate is a pigment for priming. Of these, carbon black is su[XTinr. 

A surface coating protects the substrate against abrasion, moisture, light, and corrosion. The binder for the pigment and extenders is fluid before application and rigid soon after. Natural binders range from gum arable to fish oil. The first varnishes were solutions of natural resins, having transparency, hardness, amorphous structure, and little permanence. 

Synthetic resins form the heart of the paint industry. The tw o main types of synthetic resins are condensation polymers and addition polymers. Condensation polymers, formed by condensation of like or unlike molecules into a new, more complex compound, include polyesters, phenolics.. iniino resins, polyurethane, and epoxies. Addition polymers include polyvinyl acetate, polyvinyl chloride, and the acrylates, 

Alkyds are the most widely used protective-coatings at 1-million pounds annual world consumption. Brittle and insoluble in common solvents, they are manufactured with a plasiici/m. -Manipulating the molecular structure produces alkyds with the desirable properties. 

Phenol (Cf HjOH) reacts readily with aldehydes to form oil. soluble compounds called phenolic resins that dry rapidly, are hard, chemical and abrasion resistant, but they tend to yellow with age. 

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HOCH2C = CCH2OH. White solid, m.p. 58 C, b.p. 238- C prepared by the high pressure reaction between ethyne and methanol and also from BrMgCCMgBr and methanal. Used in electroplating (Ni), as a corrosion inhibitor, and in paint and varnish removal. 

CoAsS, are also used as sources. The ore is roasted and Co is precipitated as the hydroxide and then reduced to Co with carbon (hep below 417 - C, cep to m.p.). The metal is silvery white and readily polished. It dissolves in dilute acids and is slowly oxidized in air. Adsorbs hydrogen strongly. The main use of cobalt is in alloys. Cobalt compounds are used in paints and varnishes, catalysts. Cobalt is an essential element in the diet. World production 1976 32 000 tonnes metal. 

Bitumen paints and varnishes, which are mixtures of hard bitumen, usually oxidized, and a light or very light solvent. 

Hydrocarbon resins are used extensively as modifiers in adhesives, sealants, printing inks, paints and varnishes, plastics, road marking, flooring, and oil field appHcations. In most cases, they ate compounded with elastomers, plastics, waxes, or oils. Selection of a resin for a particular appHcation is dependent on composition, molecular weight, color, and oxidative and thermal stabiHty, as weU as cost. A listing of all hydrocarbon resin suppHers and the types of resins that they produce is impractical. A representative listing of commercially available hydrocarbon resins and their suppHers is included in Table 6. 

ISO 7724-1-1984, CIE Standards Colorimetric Observers Paints and Varnishes—Colorimetry, Part 1, Principles-, ISO 7724-2-1984, Part 2, Colour Measurement, ISO, Geneva, Swit2erland. 

ISO 7724-3-1984, 1st ed.. Paints and Varnishes—Colorimetry, Part 3, Calculation of Colour Differences, ISO, Geneva, Switzerland. 

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

Other Derivatives and Applications. Copolymerization of DCPD with other unsaturated substances has received wide attention, and several useful appHcations have been developed. With drying oils (qv) thermal copolymerization leads to the production of resinous products, the so-called bodied oils, that give improved drying and result in paint and varnish coatings of greater resistance to weathering. 

Paint and varnish manufacturing Resin manufacturing closed reaction vessel Varnish cooldng-open or closed vessels Solvent thinning Acrolein, other aldehydes and fatty acids (odors), phthalic anhydride (sublimed) Ketones, fatty acids, formic acids, acetic acid, glycerine, acrolein, other aldehydes, phenols and terpenes from tall oils, hydrogen sulfide, alkyl sulfide, butyl mercaptan, and thiofen (odors) Olefins, branched-chain aromatics and ketones (odors), solvents Exhaust systems with scrubbers and fume burners Exhaust system with scrubbers and fume burners close-fitting hoods required for open kettles Exhaust system with fume burners... 

Thin coatings consist of paints and varnishes, which are applied as liquids or powdered resin with a thickness of about 0.5 mm [e.g., epoxy resin (EP) [2]]. Typical thick coatings are bituminous materials [3] and polyolefins [e.g., polyethylene (PE) [4]], thick coating resin combinations [e.g., EP tar and polyurethane (PUR) tar [2]] as well as heat-shrinkable sleeves and tape systems [5]. 

Because of their wide compatibility and solubility, coumarone resins are used considerably in the paint and varnish industry. The resins also find application as softeners for plastics and rubbers such as PVC, bitumens and natural rubber. 

Synthetic resins are extensively used, e.g., in surface finishes, in the fabrication and repair of boat and motor vehicle bodies, in the manufacture of laminated boards, for electrical components, in pattern making and in paints and varnishes. Non-rubber adhesives made from fish glues and from cotton derivatives (e.g. cellulose acetate) tend not to be sensitizing but, depending upon composition and the manner of use, many other types may pose significant dermatitic and fume hazards. 

Wastes from the manufacture, formulation, supply and use (MFSU) of coatings (paints, varnishes and vitreous enamels), adhesive, sealants and printing inks 0801 wastes from MFSU of paint and varnish... 

Lack-industrie,/. (paint and) varnish industry, -lack, m. lac lake, -lasurfarbe,/. transparent varnish color, -laus,/. lac insect, -lausfarb-stoff, m. lac dye. -leder, n. japanned leather, patent leather, -leinol, n. linseed oil for varnish. -losungsmittel, n. lacquer solvent. 

Mesityl oxide is produced by the dehydration of acetone. Hydrogenation of mesityl oxide produces methylisobutyl ketone, a solvent for paints and varnishes ... 

All paints consist of a binder (sometimes called a medium) and pigment. Materials consisting of binder only are called varnishes. Most paints and varnishes contain solvent in order to make the binder sufficiently liquid to be applied. The combination of binder and solvent is called the vehicle. Some paints are available without solvent (e.g. solventless epoxies) but these generally require special methods of application (e.g. application of heat) to reduce the viscosity. 

By means of an ingenious instrument which measured the wetness of a painted surface. Gay found that although the relative humidity of the atmosphere varies appreciably, this is not reflected in the behaviour of paint films. He found that under normal conditions paint films are saturated with water for about half their life, and for the remainder the water content corresponded with an atmosphere of high humidity furthermore, the relative humidity of sea-water is about 98%. It follows from Table 14.3 that the rate at which water passes through paint and varnish films is many times greater than the water consumed by an unpainted specimen exposed under industrial conditions or immersed in the sea. 

When samples of about 1 cm were taken from a single cast film of 100 X 200 mm of a number of paint and varnish films, their resistances varied with the concentration of potassium chloride solution in one of two ways (Fig. 14.2). Either the resistance increased with increasing concentration of the electrolyte (inverse or / conduction) or the resistance of the film followed that of the solution in which it was immersed (direct or D conduction). The percentage of / and D samples taken from different castings varied, but average values for a number of castings were 50% D for the pentaerythritol alkyd and the tung oil phenol formaldehyde varnishes, 57% for urethane alkyd, 76% for epoxypolyamide and 78% for polyurethane varnishes... 

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