J Polym Environ
acids to CA films for enhancing the biodegradation [76]. In
US Patent 6,571,802 Yamashita proposed combining the
acid with a stabilizing agent which releases the acid upon
contact with water, thus preventing the additives from
deacetylating the CA and generating acetic acid before
disposal [77]. Robertson in US Patent Application 2009/
0151738 disclosed the idea of making an enhanced
degradable cigarette filter by adding a hydrolysis causing
additive to the filter. The idea is said to require the use of a
coating or pill to hold the hydrolysis agent until the filter is
discarded, then the additive would be released upon contact
with water [78].
In US Patent 6,133,439 Buchanan et al. described
environmentally non-persistent cellulose ester fibers based
upon using a low DS polymer (DS = 2.0–2.2) and anatase
TiO2 [79]. The benefit of this blend was to enhance both
biodegradation and photodegradation in fibers simultaneously and allow synergy between the two mechanisms.
Ishigaki et al. explored this synergy further by evaluating
the benefits of UV irradiation on the enzymatic degradation
of CA fibers without the presence of a photocatalyst like
TiO2 [80]. The UV light resulted in a decrease in the
molecular weight of CA, but did not affect the DS. The
removal of the lower molecular weight material allowed an
increase in surface area, and thus better assess for the
cellulase enzyme. Jang et al. [69] studied the effect of
cellulase degradation on films with anatase TiO2 nanoparticles with UV irradiation. They found that the UV light
significantly changed the surface properties by increasing
the hydrophilicity and lowering the DS. Both these changes
are believed to enhance the enzymatic degradation.
In addition to mixed modes of degradation, one could
choose optimum product designs to enhance disintegration.
A large amount of CA polymer is used to make cigarette
filters, which are often discarded and become litter. Disintegration can be influenced by many factors including:
rainfall, sunlight, biological agents, temperature, atmospheric oxidants, air pollutants, and mechanical agitation.
Various ideas for enhancing smoke filter disintegration
have been patented. Rapid disintegration is a key step in
the disappearance of a discarded litter item, and it also
allows enhanced degradation rates. For example, rapid
water disintegration can be designed directly into consumer
products, and thus reduce visible litter while enhancing
degradation [81–86].
The disintegration of conventional filter cigarettes is
impeded due to the highly entangled network of the fibers,
plus the structure is reinforced by the addition of plasticizers fusing the fibers together. When investigating the
effect of triacetin plasticizer on degradation Haynes and
coworkers came to the conclusion that there was no effect
on the percentage weight loss of the filter due to the
presence or absence of the plasticizer when exposed to the
123
environment [66]. There was only a visible difference in
appearance between the two samples. The sample without
the plasticizer had a less defined shape resembling a discarded cotton ball.
Early disclosures of the concept of a disintegratable
cigarette filter were in US Patents 4,022,740 and 4,074,724
by Morie and Sloan. The concept was to bond the individual fibers in a filter with water soluble polyester polymers which would dissolve upon prolonged exposure to
water and release individual fibers [81, 82]. Tsugaya et al.
[83] disclosed in US Patent 5,947,127 the bonding of
individual fibers with particulate hot-melt adhesive in place
of conventional plasticizers, thus allowing water
disintegratability.
In 1996, new