Solvents aqueous cleaners

Cleaning, the removal of unwanted matter, is the beginning of the treatment cycle for metal. The unwanted matter may be carbon smut, welding flux, ink, oxidation products, oil, fingerprints, or other material. Cleaners may be classified as solvent-based or aqueous. Within the aqueous class there are many subclasses, the most important of which are the alkaline cleaners. There are also a variety of ways to apply cleaners. As of the mid-1990s, solvent-based cleaner usage is declining. 

Butyl glycol ethers, the largest volume derivatives of -butyl alcohol used ia solvent appHcations (10), are obtained from the reaction of 1-butanol with ethylene oxide. The most important of these derivatives, 2-butoxyethanol, is used principally ia vinyl and acryHc paints as well as ia lacquers and varnishes. It is also employed ia aqueous cleaners to solubilize organic surfactants. 2-Butoxyethanol [111-76-2] has achieved some growth at the expense of the lower alkoxyethanols (ie, methoxy and ethoxyethanol) because of 2-butoxyethanol s lower toxicity. 

Diphase Cleaning. Use of an organic solvent top layer over a mild aqueous cleaner solution was popular for aiding in the removal of buffing compounds, especially on zinc base die castings. Use of this diphase cleaning has declined with the decline in buffed zinc castings. 

Semi-aqueous cleaners based on halogen-free solvents, advantages and disadvantages... 

Semi-aqueous cleaners usually are formulated for very specific applications. No user considering cleaning with the semi-aqueous process should adopt it without a legitimate demonstration of operation of the solvent mixture/water decanter without the actual soil components present. Of secondary but significant importance is a demonstration of the immersion and spray cleaning operations with actual soil components. 

Butyl glycol ethers such as 2-butoxyethanol are the largest-volume derivatives of n-butanol used in solvent applications. They are used in vinyl and acrylic paints, lacquers, varnishes, and aqueous cleaners to solubilize organic surfactants. 

The term semi-aqueous cleaners refer to cleaners comprised of solutions of natural or synthetic organic solvents that are used in conjunction with water in some part of the cleaning cycle. These cleaners are generally biodegradable. In the metal cleaning industry, the semi-aqueous cleaners are also called emulsion cleaners. 

Water-miscible semi-aqueous cleaners include low molecular weight alcohols, ketones, esters, and organic amines. Table 13.4 gives some properties of water-miscible cleaners. N-methyl-2-pyrrolidone-based solvents have a high solvency for a number of contaminants and are completely water-soluble. Acetone (CH3COCH3) removes heavy oils quite effectively hut tends to leave a residue and it is also quite flammable. Acetone cleaning or wipeclean should be followed by a methanol rinse or wipeclean to remove the residue. 

---