3 RECENT INNOVATIONS

Organic solvents that function as weak acids and bases may offer the best alternative to chlorinated hydrocarbons. One promising substitute is N-methyl-2-pyrrolidone, which has proven capabilities as a solvent for a wide variety of polymers. At least one patent has been issued for a paint stripper including N-methyl-2-pyrrolidone as a major ingredient (Francisco 1988).

West (1991) suggests that a formulation based on the dimethyl esters of mixed acids, such as adipic or succinic, may produce a slower-acting or more specific paint remover that may be effective for art conservation purposes. He states that the dimethyl esters are available through DuPont Company. The introduction of dimethyl esters may be the most exciting recent innovation in the paint stripper industry. 3M has recently begun marketing a product, Safest Stripper, that lists water, dimethyl adipate, and dimethyl glutarate as its primary ingredients. A positive review of this product has been published (Capotosto 1989).

Dumond Chemicals markets a series of paint strippers under the product name Peel-Away. In this system the paste is applied to the substrate and then covered by a fibrous laminated cloth. The cloth is designed to slow the rate of solvent evaporation and assist in clearance. When the stripping job is finished, the cloth is removed with the paint and paste adhering to it. The substrate is then washed and neutralized. The technical data supplied by Dumond Chemicals on the different Peel-Away strippers was not specific enough for inclusion in the formula listings at the end of this report. Peel-Away 1 is alkaline based (sodium hydroxide) and formulated for interior and exterior paint removal. Peel-Away 4 is acid based and designed for use on a cementitious substrate. Five of the Peel-Away series are cold solvent strippers with specific mention of methylene chloride in two of the products. Recently, Peel-Away 6 has been introduced; this “safe remover” employs both dimethyl esters and N-methyl-2-pyrrolidone.

Richard Wolbers, associate professor at the University of Delaware, has introduced varnish remover systems based on organic solvents gelled in a water-soluble, polyacrylic acid resin (Carpobol Resins, manufactured by BF Goodrich Industries). These water-soluble resins require an activator selected from a group consisting of cationic surfactants, nonionic surfactants, simple organic bases, or combinations thereof in an aqueous solution. Examples of suitable simple organic bases include isopropanolamine, triethanolamine, diethan-olamine, and monoethanolamine. Surfactant types include polyoxyethylene (15) cocoamine and bis (2-hydroxyethyl) cocoamine (Ethomeen C/25 and Ethomeen C/12, manufactured by Akzo Chemicals Inc.). These solvent-based systems may be engineered to remove specific coatings or to not react with a specific type of substrate. The patent offers a more detailed description of the principles behind these systems (Wolbers 1991).