Handbook of Solvents - George Wypych - ChemTech - Ventech!

18.3 Indoor air pollution by solvents 1235
the required properties may be selected. The influence extends to dissolving of binders, reduction
of paint viscosity, pigment wetting, etc. Optimized dissolving of binders can be
achieved by selecting the appropriate solvent mixtures, in which the density approaches that
of the binder solubility range. Nevertheless the selection of an optimized solvent mixtures is
difficult because there are conflicting requirements and outcomes. 2,5 On one hand, the
chemical nature of the solvents should be similar to those of the binder to improve the flow
but on the other hand, the solubility and hydrogen-bonding abilities of the solvents should
be at the edge of the binder solubility range, because this results in rapid drying with low retention
of solvents.
18.3.2 OCCURRENCE OF SOLVENTS IN PAINTS AND VARNISHES
18.3.2.1 Solvents in products
Classification
Authorized commissions in Germany describe various groups of solvents in paints and varnishes:
The Association of Varnish Industry VdL (Verband der Lackindustrie) classifies solvents
generally used in paints and varnishes in the following groups: 4 Aliphatics, alcohols,
aromatic hydrocarbons, esters, glycols, glycol ethers, ketones, terpenes, gasoline, water.
The commission of Hygiene, Health and Environmental Protection (Hygiene,
Gesundheit und Umweltschutz) which belongs to the German Standards Commission DIN
(Deutsches Institut für Normung e.V.) also describes solvents which may be present in
paints as follows: 10
• Aliphatics (white spirit, turpentine substitutes, cyclohexane)
• Aromatic hydrocarbons (toluene, xylenes, naphtha, styrene)
• Alcohols (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, glycols)
• Ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone)
• Esters (methyl acetate, ethyl acetate, butyl acetate)
• Others: methylpyrrolidone, oils of turpentine
Chlorinated hydrocarbons are not contained in the above list. Benzene is not included
as it is obsolete, although it is sometimes found in some petroleum solvent-based paints.
Shortcomings
The description of paints and varnishes is usually neither complete nor reliable:
• Instructions and comments from manufacturers and suppliers differ in quantity and
quality. Usually manufacturers or suppliers are not committed to indicate the exact
details of their product’s composition. They often omit information (e.g.,
information concerning product components, additives or by-products).
• Lack of standards. In Europe there are some mandatory standards concerning
products used in construction (e.g., asbestos, formaldehyde in particle board,
organic solvents in certain activities and installations are prohibited).
• Solvents or other organic compounds may be present, in low concentrations, in
some products (even in water-based paints), e.g., as additives or by-products
although there is no reference to them.
• Additives (e.g., low molecular compounds such as esters or glycol ethers with high
boiling points) serve as aids for the formation of films, in repelling water, in
assisting plasticization or for other functions. In solvent-based paints, additives or
diluting agents are often intentionally mixed in.