Handbook of Solvents - George Wypych - ChemTech - Ventech!

14.31 Wood furniture 1043
REFERENCES
1 EPA Office of Compliance Sector Notebook Project. Profile of the Water Transportation Industry.
US Environmental Protection Agency, 1997.
14.31 WOOD FURNITURE
George Wypych
ChemTec Laboratories, Inc., Toronto, Canada
The US wood furniture industry operates over 11,000 manufacturing facilities which employ
over 250,000 people. Total sales are over $22 billion. Several operations use solvents,
including veneer application (adhesives), derosination (certain types of wood contain rosin
which may interfere with the effectiveness of certain finishes; rosin is removed by application
of a mixture of acetone and ammonia), pretreatment (coating contains coalescing solvent
(slow evaporating) and diluent (fast evaporating), a new UNICARB � technology uses
carbon dioxide in the mixture with a coalescing solvent which eliminates the need for a diluent),
several finishing operations (stains, paints, fillers, inks used to print simulated wood
grain on plywood, topcoat, and cleaning liquids). Nitrocellulose lacquers are commonly
used in the USA; polyurethane and unsaturated polyester finishes are still rarity. Solvents
and thinners used in paints include toluene and xylene. Adhesives usually contain solvents
such as methyl isobutyl ketone, methyl ethyl ketone, xylene, toluene, and
1,1,1-trichloroethane. Table 14.31.1 shows the relative amounts of VOC emissions from
different finishing components depending on furniture type and type of process used. The
long process consists of applications of 3 or more coats of stain, a washcoat, a filler, a sealer,
a highlight, and two to three topcoat applications. In the short-sequence process two stain
coats are applied, followed by a washcoat, a sealer, and two top coat applications. Office
furniture uses only one application of a stain, a sealer, and a topcoat.
Tables 14.31.2 and 14.31.3 provide data on the reported releases and transfers of solvents
by the US furniture and fixtures industry. Toluene, xylene, methanol, and methyl
ethyl ketone are released in the largest quantities. The furniture and fixtures industry is one
of lesser contributors of VOCs releases and transfers among the US manufacturing industries.
Several alternative technologies are under development and some are at the field trial
stage. 3-12 Waterborne clear varnishes are being used increasingly but the market is still dominated
by solvent-based varnishes. One reason may be that waterborne varnishes are 2-3
times more expensive than solvent-based products. 3 It is also not clear if waterborne varnishes
have lower odor and can be applied at the same rate as solvent-based products.
Waterborne varnishes have one important advantage in clear coatings for they have no color
therefore the natural wood color is more vivid. Two-component water-based polyurethane
coatings have been introduced recently. 4 They have a very low VOC content and have very
good drying speed, gloss, and potlife. The drying rate and potlife are controlled by the ratio
of isocyanate and hydroxyl components. Increasing this ratio increases drying speed but
decreases potlife. However, at 4 hours, potlife is acceptable. Polyurethane dispersions are
used in furniture adhesive applications, and are especially useful in the lamination of
kitchen tables. 5