Handbook of Solvents - George Wypych - ChemTech - Ventech!

14.23 Printing industry 1021
nated hydrocarbons. 3 An additional requirement was to optimize the solvent mixture to
prevent swelling of the rubber in blanket cylinders and rollers. It is predicted that the European
industry will increase rate of the introduction of radiation-cured inks and eliminate
isopropanol from fountain solutions. 4 It is expected that radiation-cured flexographic inks
will grow by 30%/year in the next five years. 5 In Germany, 70-80% of emissions or 47,000
ton/year will have to be eliminated by the year 2007. 6 Beginning in 1999, the UK industry
must keep VOC concentration below 5 tonnes/year per plant. 7 VOC concentration in outside
atmosphere must not exceed 150 mg/m 3 (50 mg/m 3 if there is more than 5% aromatic
solvents). Reactive hot melts are being used in book binding. 8 This will eliminate emissions
from currently used solvent adhesives.
Solvent replacements are not the only solution at hand. Solvent-containing systems often
give better quality than replacement systems, therefore methods have been developed to
make the solvent based materials more acceptable. A soil bed biofiltration system was
tested in California with excellent results. 9 This biofilter is a bed of soil impregnated with
microorganisms which use VOC as their food. Present California regulations require that
such a treatment system has a 67% capture and VOC destruction efficiency. The new
method was proven to have 95.8% efficiency. In addition to environmental issues with solvents,
the printing industry has addressed the source of their raw materials. Present systems
are based on petroleum products which are not considered renewable resources. Terpenes
are natural products which are now finding applications in the print industry. 10 In Denmark,
of 70% cleaning solvents are vegetable oil based. These and other such innovations will
continue to be applied to reduce solvent use and emissions. It is also reported 10 that water-based
system replaces fountain solutions.
Other factors are driving changes. Odors in packaging materials and the migration of
solvent to foods are unacceptable. Most odors in packaging materials are associated with
process and coalescing solvents. 11 Foods which do not contain fat are more susceptible to
the retaining the taste of solvents. Printing inks which may be acceptable for foods containing
fat may not be suitable for fat-free applications (see more on this subject in Chapter
16.1). 12
Many recent inventions have also been directed at solving the current environmental
problems of printing industry. 13-21 The solvent in gravure printing inks not only contribute to
pollution but also to the cost of solvent recovery and/or degradation. A new technology is
proposed in which a solvent free ink with a low melting point can be processed in liquid
state and then be solidified on cooling. 13 A non-volatile solvent for printing inks was developed
based on a cyclic keto-enol tautomer and a drying oil. 14 An alcohol soluble polyamide
for rotary letterpress printing inks was developed 15
and subsequently adapted to
flexographic/gravure inks. 18 A polyamide was also used in a rotary letterpress ink which
enabled low alcohols to be used as the solvent with some addition of an ester. 16 This new ink
is compatible with water-based primers and adhesives which could not be used with solvent-based
inks. Inks for jet printers are water sensitive. One solvent-based technology was
developed using esters and glycols 17 and the other using low alcohols. 20 Another recent invention
describes aqueous ink containing some low alcohols. 19 UV and electron beam cured
ink concentrates were also developed. 21
This information from open and patent literature clearly indicates that industry is actively
working on the development of new technological processes to reduce emissions of
solvents.