|Concerns regarding the environment as well as the health and
safety of workers and consumers and consumers of solvent-based
adhesives are gaining momentum worldwide. In the United States
of America, for example, the local, state and federal governments
are setting stricter limits on plant emissions and the volatile
organic compound (VOC) content of adhesives. A combination of
factors including performance considerations, excise taxes and
regulations governing VOCs will motivate adhesive manufacturers
to evaluate advances made in water-based technology and encourage
their customers to consider solventless systems.
Lembaga Getah Malaysia has successfully developed water-based
pressure sensitive adhesives using NR latex. These novel adhesives
are particularly suitable for coating crepe paper used in
the manufacture of pressure sensitive adhesive (PSA) masking
A pressure sensitive tape is a tape which adheres to a surface
at room temperature with the aid of light finger pressure.
Typical applications of masking tapes are for painting, spraying,
carton sealing and packaging, bundling and splicing.
All the materials used in the preparation
of the pressure-sensitive adhesives are either aqueous dispersions
or solutions. Preparation of the various adhesives involves
mixing of these aqueous ingredients in the required proportions
by normal stirring. Such waterborne adhesives, being dispersions,
need to be kept agitated to prevent the adhesive particles
from settling out. Excessive stirring or pumping rates, however,
can cause foaming of the adhesive resulting in unevenness
or gaps in the applied adhesive. Another factor to consider
in the mixing process is the potential for contamination by
dirt or impurities: filtration may be effected with a system
within the piping or by pouring the adhesive over a filter.
The main advantages of waterbased adhesives
include absence of VOCs and hazardous air pollutants (HAPs),
no explosion risk, reduced generation of hazardous wastes,
lower insurance costs, and no need for solvent recovery or
air pollution control systems. There are some limitations,
however, in processing waterborne adhesives including increased
generation of wastewater and sludge, may need onsite wastewater
treatment, cleaning is more time and energy intensive, and
dry/cure ovens have higher energy consumption.