Case Study # 80
1. Headline: Substitution of organic solvent-based
flexographic printing ink on polyethylene to water-based
flexographic printing ink.
2. Background: Landskrona Emballage is a printing company
that mainly produces packages for food and sanitary
articles. The material printed is mostly polyethylene of
different qualities. The company has 40 employees and the
turnover in 1993 was US$ 3.8 million. The case study was
performed in 1991.
3. Cleaner Production Principal: The cleaner technology
principle involves material substitution of water-based
flexographic printing inks which are free from organic
solvents.
4. Description of Cleaner Production Application:
Process and Waste Information: The chemicals handled in
the production were used in the printing process and in
cleaning the printing equipment. The printing ink commonly
used contained 70% organic solvents, principally ethanol
and different glycols. When cleaning the equipment for the
presses, solvents were used which normally were included
in the printing ink.
It is important that the ink must be easy to remove from
press parts and yet have a short drying time during the
printing. Another important requirement is that the ink
has to be resistant to chemicals. The printing quality of
the inks free from volatile organic solvents on products
like bread packages, postal order material and sanitary
articles is now fully comparable with solvent based
printing quality. The modifications made on the equipment
also contributed to the printing quality.
The importance of good adherence between the printing ink
and the polyethylene film increases when printing with
water-based ink. An important factor is the level of
treating (ie the change of the surface tension on the
polyethylene film). Treating equipment was installed in
line on the press to achieve better control over the level
of treatment which is influenced by, for example, the
amount of slip agent and the storing time. In order to
deal with excess ozone, an ozone converter was included in
the equipment.
Traditionally, centrifugal pumps are used to pump ink from
ink fountains to an ink train. Problems, including scum
formation and packing caused by the build-up of layers of
dried ink, arise with this form of pumping when using
water based ink. The problems can be almost completely
eliminated by using peristaltic pumps. All six ink trains
in the presses were equipped with peristaltic pumps.
To limit the amount of ink transferred to a roller,
different types of blades are used to rake off ink excess.
The water-based printing technology required an effective
blade system, something which lead to the installation of
a double blade enclosed chamber system. Problems with
frothing between the rollers could in this way be avoided.
The water based printing ink dries slower than organic
solvent based ink. The drying process is therefore
important. Efforts have been made to modify and make the
drying process more effective and the drying units between
different ink trains were therefore re-built.
The solvent-based printing ink was easy to wash away with
ethanol and ethylene glycol. Since the new water-based ink
is harder to remove, it was necessary to change the
washing routines. The longer washing time can be
compensated for by less need for cleaning of the new
equipment such as the chamber blades and peristaltic
pumps. The new cleaning with water also clearly improves
the work environment.
Since 1991, all printing is being done with water-based
inks in the modified press. The emission of solvents has
in the printing line been considerably reduced from 20
tons a year to nearly zero.
Scale of Operation: The company employs 40 people and the
turnover in 1993 was US$ 3.8 million. The equipment is
available on the market
Material/Energy Balances and Substitutions:
Material Category Quantity Before Quantity After
Waste Generation
discharge of organic
solvents 20 tons nearly 0
Feedstock Use N/A N/A
Water Use N/A N/A
Energy Use N/A No increase
5. Economics: The total investment cost in technology was
US$ 304,000 (1990).
6. Advantages: Generally, the following advantages can be
ascribed to the water-based technology in relation to
solvent-based printing inks:
-Considerable reduction of the discharge of solvents
-No inflammable printing ink
-Improved working environment
-Improved environmental reputation in society and public
relations through visible environmental improvement
activities
7. Constraints: Not reported
8. Contacts
Lars Siljebratt
The Foundation of TEM,
Asumsgatan 38 275 37 Sjobo
Sweden
TEL: +46-416-273 00
FAX: +46-416-273 12
Landskrona Emballage AB
Bevergatan 1
Box 4084
261 04 Landskrona
Sweden
Tel: +46-418-169 70
9. Keywords: Sweden, printing, flexographic printing,
material substitution, ink, polyethylene, peristaltic
pump.
10. Reviewer's Comments: This case study was translated from
Swedish and submitted by the Swedish Foundation of TEM to
UNEP IE. It was edited by UNEP IE in July 1995, but has
not undergone a formal technical review.