This document summarizes research into developing more sustainable waterborne polyurethane coatings using bio-based materials. It discusses two main strategies - hard segment functionalization and soft segment functionalization. Hard segment functionalization involves incorporating ionic groups directly into the polymer backbone during synthesis. Recent work used dimethylolpropionic acid for this. Soft segment functionalization grafts ionic groups onto bio-based polyols, such as grafting mercaptopropionic acid onto a vegetable oil-based polyol using UV-mediated thiol-ene reactions, making the polyol more hydrophilic and dispersible in water. The functionalized polyol can then be used to synthesize waterborne polyurethanes. The

1. BIOBASED WATERBORNE POLYURETHANES FOR COATINGS
Jevgenij Lazko, Loïc Poussard, Jérôme Mariage, Jean Marie Raquez, Philippe Dubois
jevgenij.lazko@materianova.be
Materia Nova, Laboratory of Polymeric and Composite Materials (SMPC), Avenue Copernic 1, 7000 Mons, Belgium
Center of Innovation and Research in Materials & Polymers (CIRMAP), University of Mons (UMons), Place du Parc 23, 7000 Mons, Belgium
Copyright : photo © Denis Lecuyer
REFERENCES
1. K.L. Noble, Progress in Organic Coatings. 1997, 32, 131.
2. L. Poussard, J. Lazko, J. Mariage, J.M. Raquez, P. Dubois, Progress in Organic Coatings. 2016, 97, 175.
3. C. Fu, Z. Zheng, Z. Yang, Y. Chen, L. Shen, Progress in Organic Coatings. 2014, 77, 53.
INTRODUCTION
The evolution of the regulatory requirements relevant to health,
safety and environment is currently driving research into finding
new alternatives for polyurethane-based coatings. Development of
waterborne polyurethanes (WPU) was undoubtedly a major
technological advance that significantly reduced volatile organic
compounds emissions [1]. Further sustainability improvements can
be achieved replacing petro-based chemistry by renewable bio-
based alternatives, using for instance polyols issued from abundant
and low cost agro-industrial oils, and particularly of unsaturated
ones. The selected polyols for the present studies were fatty dimer
functionalized Veopur polyols, recently developed by Vandeputte
Oleochemicals.
HARD SEGMENT FUNCTIONALIZATION
Due to the intrinsic hydrophobicity of plant oil-based polyols, the predominant
strategy to obtain WPU consisted in hard segment functionalization: the
incorporation of ionic hydrophilic segments directly into polymer backbone during
the synthesis. Dimethylolpropionic acid (DMPA) neutralized with triethylamine
(TEA) was the couple of charges improving amphiphilic properties used in our
recent works about the synthesis of biobased WPU for coating applications and the
influence of process parameters on their physicochemical, mechanical and thermal
properties [2]. Characterizations showed that WPU formulations based on
renewable polyol Veopur and H12MDI could be considered as promising materials
for sustainable coatings. An appropriate choice of hard segment content might be
used to meet specific requirements for various applications and supports (wood,
metal, walls).
ACKNOWLEDGEMENTS
This research was supported by
the Cornet Program in the frame
of the “Cost-effective biopolymer
interior coatings” Biocoat project
(Convention n° 1317997).
SOFT SEGMENT FUNCTIONALIZATION
An alternative strategy, soft segment functionalization, consists on grafting charges directly on the biobased polyols. This functionalization brings new
amphiphilic properties to the polyols, enhancing their hydrophilic character and eventually their dispersability in water. Such modified polyols may finally
react with diisocyanates to form WPUs. In this respect, solvent-free UV-mediated thiol-ene grafting of mercapto-carboxylic acids on polyol might represent a
sustainable environmentally friendly approach fully considering intrinsic chemical assets of unsaturated vegetal oils [3].
0,511,522,533,54
[ppm]
86 %
Veopur-MPTEA
34 %
Veopur
2,42,52,62,72,82,933,1
2,42,52,62,72,82,933,1
Veopur
34 %
86 %
MPTEA
TEA
Veopur-MPTEA
1H NMR spectra of the reference Veopur, MPA grafted Veopur and
functionalized Veopur after neutralization with TEA.
The soft-segment functionalization strategy recently investigated in
Materia Nova Research Center consisted on grafting mercaptopropionic
acid (MPA) on biobased polyol Veopur double bonds, using solvent-free
UV mediated thiol-ene reaction performed in bulk. Grafted carboxylic
moieties were then neutralized by TEA and, in the last step, this
functionalized water dispersable polyol was finally polymerized with
commercial water soluble polyisocyanates to form WPU. The influence of
key process parameters on grafting efficiency was investigated,
modification being followed by Iodometric titration and 1H NMR. The
emphasis was also placed on the influence of grafting rate on water
dispersability of functionalized polyols and coating properties of
corresponding WPUs.
HO
O
O
HO
O
O
HO
O
O
HO
O
O
COO
- +
HNEt3
S
S
COO
- +
HNEt3
NHCO
O
OCHN
O
COO -
NHCO
O
HNEt3
+
OCN NCO
NHCO
O
OCHN
O
NHCO
O
OCHN
O
COO -OCN NCO HO OH
COO
HNEt3
+
-
HNEt3
+
2) Dispersion in water
3) Addition dispersable polyisocyanate
1) 50 wt% MEK, 80°C, 5h
2) Addition of water
3) MEK removal
1) Solvent-free
photochemical
thiol-ene grafting
UV
HS
COOH
NEt3
Biobased Polyol
Hard segment ionic
functionalization
Soft segment ionic
functionalization
Waterborne Polyol
Waterborne Polyurethanes