Lacquered can

In order to prevent recurrence of the corrosion, a lacquer can be appHed. Alternatively, the environment of the object can be strictiy controlled with regard to relative humidity and pollutants. 

Many older finishes can be removed with single solvents or blends of petroleum solvents and oxygenates. Varnish can be removed with mineral spirits, shellac can be stripped with alcohols, and lacquers can be removed with blends of acetates and alcohols (lacquer thinners). The removal mechanism is one of dissolving the coating, then washing the surface or wiping away the finish. This method is often used to reamalgamate or liquefy old finishes on antique items of furniture. 

Acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, ethyl acetate, and tetrahydrofuran are solvents for vinyhdene chloride polymers used in lacquer coatings methyl ethyl ketone and tetrahydrofuran are most extensively employed. Toluene is used as a diluent for either. Lacquers prepared at 10—20 wt % polymer sohds in a solvent blend of two parts ketone and one part toluene have a viscosity of 20—1000 mPa-s (=cP). Lacquers can be prepared from polymers of very high vinyhdene chloride content in tetrahydrofuran—toluene mixtures and stored at room temperature. Methyl ethyl ketone lacquers must be prepared and maintained at 60—70°C or the lacquer forms a sohd gel. It is critical in the manufacture of polymers for a lacquer apphcation to maintain a fairly narrow compositional distribution in the polymer to achieve good dissolution properties. 

The epoxy-acrylic resin referred to above is a graft copolymer prepared by the polymerisation of acrylic monomers in the presence of the epoxy resin in such a way that grafting of the acrylic onto the epoxy takes place. Water dispersibility is achieved by neutralising carboxyl groups in the acrylic polymer chain with ammonia or amine. Amino or phenolic resins are used as crosslinkers. Alternatively, solvent-borne epoxy-amino or epoxy-phenolic lacquers can be used. 

Most natural foods contain small amounts of tin but canned foods may have significant tin levels (NAS 1977 WHO 1980). Tin concentrations in fresh meats, cereals, and vegetables reportedly range from 0.1 to 1.0 mg tin/kg (Schafer and Femfert 1984). However, concentrations of tin ranging from 1.8 to 500 mg/kg have been reported in canned foods (Schafer and Femfert 1984 Sherlock 1987), with usual values below 100 mg/kg (NAS 1977). Foods from all- lacquered cans usually had tin concentrations below 25 mg/kg (WHO 1980). Current data from the Can Manufacturers Institute (CMI 1988) indicate that more than 90% of tin-lined cans used for food today are lacquered. Only light colored fruit and fruit juices are packed in unlacquered cans, since tin helps maintain the color of the fruit. 

The tin content of foods has been reported by several investigators (64-67). Storage of food in tin-alloyed cans increases the tin concentration in foodstuffs bottled foods have essentially no tin (67). The practice of coating cans with lacquer — used widely in industrialized countries, but not in some developing nations (65) — reduces the leaching of tin, but even with lacquer cans. Imperfections In the coating (pinholes) allow contact of foods with metal. The concentration of tin in selected foods packaged in various types of cans is illustrated in Table VI. 

Lacquer can be used on such varied items as furniture and small brooches (Fig. 12.5). Boxes have always been very popular. 

The possible roles of nails (fingers and toes) in exposure to chemicals include direct contact with the cuticle and nail, inhalation from volatilization of a chemical applied to the nails, and oral intake via nail biting and finger sucking. Consumer products of relevance include nail lacquers ( polishes ) and nail lacquer removers applied via various means (applicator, cotton ball, etc.). Also, handwashing, dishwashing, shampoo, hard surface cleaning, etc., products would involve nail contact, as would contact with residential water and soil, and paints and paint removers, and petrol. Nail lacquers can include toluene, 1,1,1-trichloroethane, and phthalates, while nail lacquer remover can include ethyl acetate. 

Foil hard 0.018-0.020 mm plus 6-8 g/m2 wax, 4-12 g/m2 vinyl type lacquer or PVdC coating of 10 g/m2 and above. Lowest foil gauge in use is 15 Pm. Note that special HS lacquers can be formulated to adhere to PVdC, Aclar, PP, etc. 

Methylisobutylketone (MIBK) which is used as solvent for inks and lacquers can be prepared from acetone through a catalytic three-step process base-catalyzed production of diacetone alcohol (DA), acid dehydration of (DA) into mesityloxide (MO) then hydrogenation of (MO) on a noble metal ... 

Is PEG always a suitable preservative In my opinion, there are very few situations in which PEG is not suitable as a preservative for wet wood. One, however, is obvious when the object is going to be kept outdoors. The solubility of the PEGs in water makes them leach when it rains. Even with a sheltering roof, the hygroscopicity of the PEGs makes them leach at relative humidities above 80%. A coating of lacquer can protect the object in an outdoor situation and delay the effect of the PEG hygroscopicity, but it cannot be prevented. 

Manufacturing Ethyl acetate (CH3COOCH2CH3), a solvent used in making varnishes and lacquers, can be produced by the reaction between ethanol and acetic acid. The equilibrium system is described by the equation CH3COOH -F CH3CH2OH... 

Today, coatings technology has advanced to the point where these distinctions are no longer meaningful paints can contain resins, varnishes may be pigmented, enamels can contain oils, and lacquers can contain resins ... 

Lacquers are clear, synthetic coatings, most often cellulose-based (such as nitrocellulose often modified with a resin, cellulose acetate, methyl cellulose, ethyl cellulose, and benzyl cellulose) that dry through evaporation of a solvent. Lacquers can be made from a liquid lacquer base, a starting point for speciality lacquers (e.g., automotive) which most often contain the film-forming material in concentrated solution with or without other components. The base may be up to 25% nitrocellulose. 

The principal application of solid Thiokol elastomers is as gaskets, O-rings, gasoline, and fuel hose lines, gas meter diaphragms, and as rollers, which are used for lacquering cans. 

Chapter 9 it was explained that the viscosity of an emulsion is little greater than that of the continuous phase. It is not influenced by dispersed phase polymer molecular weight and is influenced by dispersed polymer concentration only at high concentrations. So, if the film-former of a lacquer can be emulsified, then, in principle, the lacquer can be supplied as an emulsion at much higher solids. 

The resistance of the outside lacquer can be tested using an aggressive preparation, for example a cream containing methyl nicotinate appeared to be quite aggressive towards the external lacquer. 

Nitrocellulose lacquers can be formulated with a large number of ketone solvents. Acetone, a fast evaporating solvent, will tolerate large additions of cheaper aromatic diluents to the nitrocellulose lacquers. The low viscosity of acetone and the hydrocarbon additions affords low solution viscosities. Other ketones that are useful as nitrocellulose solvents and that have high aliphatic and aromatic dilution ratios include MEK and MIBK. Additional ketones that find use in nitrocellulose lacquers include methyl /i-amyl ketone, methyl isoamyl ketone, dipropyl ketone, diisobutyl ketone, and cyclohexanone. Selection of the ketone often will depend on the desired evaporation rate. 

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