Utilization of Green Materials for Coating Applications - Green Materials from Plant Oils - page 300

pollutant (HAP) characteristics, and are viable alternatives to petroleum-
based coalescing solvents such as Texanol s . Dimethyl succinate is also used
in the synthesis of dimethyl succinyloyl succinate, which is further pro-
cessed to produce quinacridone pigments. 50 Methyl soyate (soybean oil
methyl ester) offers very low flammability, a Kauri-butanol (Kb) value of 58,
very high flash point (4360 1F), low VOC levels ( o 50 g L 1 ), low toxicity,
non-HAP status, and is useful as a coalescing solvent. 51 Ethyl lactate (ethyl
a-hydroxy propionate) is derived from corn and is a non-HAP, 100% bio-
degradable, non-carcinogenic and non-ozone-depleting coalescing solvent
(Kb value 500) used in specialty coatings, paint strippers and grati re-
movers. 52-53 Technical grade D-limonene, the major component of the oil
extracted from citrus rind, is a useful bio-based solvent with a Kb value of 67
and has better solvent properties than mineral spirits (Kb value 37). 54 Soy
Technologies, LLC markets Soyanol t , a series of compositions containing
soybean oil derivatives as viscosity and flow modifiers for solvent-based
coatings and as coalescents for waterborne coatings. 55
Reactive diluents function as solvents for resins and react into the
final film rather than evaporating after coating application, thus they
reduce viscosity without increasing VOC content. Reactive diluents prepared
from tung oil via a Diels-Alder reaction with different dienophiles,
methacryloxypropyl trimethoxysilane and triallyl ether acrylate improved the
tensile strength and tensile modulus of a long oil soybean oil alkyd without
significantly altering the elongation-at-break values. 56
12.2.7 UV-curable Coatings
The use of epoxidized palm oil, epoxidized soybean oil, epoxidized linseed
oil, epoxy norbornene linseed oil, and the naturally occurring epoxidized oil,
vernonia oil, in cationic UV-cured coatings has been reported by various
authors. 57-60 Radiation-curable acrylates have been synthesized by reactions
of epoxidized vegetable oils and acrylic acid. 61,62 The saturated fatty acids
provide flexibility, while the terminal methyl groups of the fatty acid chains
play a significant role in the delocalization of electrons around the double
bond during free radical production by UV radiation. Allnex markets a var-
iety of vegetable oil derivatives for UV coatings, e.g., epoxidized soybean oil
acrylate (Ebecryl s 860) for improved flow and leveling, fatty-acid-modified
polyester hexacrylate (Ebecryl s 450) for rapid cure, fatty-acid-modified epoxy
diacrylate (Ebecryl s 3702) for promoting pigment wetting and flow and
leveling, and fatty-acid-modified hexafunctional polyester acrylate oligomer
(Ebecryl s 870) for fast cure response. M¨ller et al. described UV-cured wood
coatings prepared with acrylated epoxidized linseed oil and characterized
their performance properties such as gloss, scratch resistance, solvent re-
sistance and adhesion. 63
Yin et al. synthesized vegetable-oil-based photo-initiators by grafting acetic-
acid-based thioxanthone and 4-(dimethylamino) benzoic acid to the backbone
of epoxidized soybean oil. 64 The vegetable oil-based photo-initiators were