Handbook of Solvents - George Wypych - ChemTech - Ventech!

14
Solvent Use in Various Industries
Attempts to reduce solvent use in the production of various materials require background
information on the current inventory, the reasons for selecting certain solvents, the effect of
various solvents on the properties of final products, future trends and the possibilities for
solvent replacement.
Information on solvent use investigates these areas. This chapter is possible only because
of a thorough evaluation by large groups of scientists and engineers assembled by US
Environmental Protection Agency. This has produced Compliance Sector Notebooks which
contain invaluable information on solvent use. Full documents can be found on the EPA
website at http://es.epa.gov/oeca/sector/index.html. These are useful in the investigation of
a particular industry. Similar data from other countries were not available but open literature
and patents have been included to help the reader to understand changes occurring in
other countries.
14.1 ADHESIVES AND SEALANTS
George Wypych
ChemTec Laboratories, Inc., Toronto, Canada
Adhesives and sealants are manufactured from a variety of polymers. Their selection and
their combinations used impact solvent selection. Most solvent systems are designed to
optimize the solubility of the primary polymer. Adhesives can be divided into ones which
bond by chemical reaction and ones which bond due to physical processes. 1 Chemically
reactive adhesives are further divided into three more categories for those that bond through
polymerization, polyaddition, or polycondensation. Physically bonding adhesives include
pressure sensitive and contact adhesives, melt, or solution adhesives, and plastisols.
Polymerization adhesives are composed of cyanoacrylates (no solvents), anaerobic
adhesives (do not contain solvents but require primers for plastics and some metals which
are solutions of copper naphthenate), 2 UV-curable adhesives (solvent-free compositions of
polyurethanes and epoxy), rubber modified adhesives (variety solvents discussed below).
Polyaddition adhesives include epoxy and polyurethane polymers which can either be
100% solids, water-based, reactive or non-reactive hot melts or contain solvents mostly to
regulate viscosity. Typical solvents include methyl ethyl ketone, acetone, mineral spirits,
toluene, and xylene. 3 Polycondensation adhesives include phenol-formaldehyde resin,
polyamides, polyesters, silicones and polyimides. With the exception of polyesters (which
require ethanol and N-methylpyrrolidone as solvents) and polyimides (which require