Tall oil fatty acid-based alkyd-acrylic copolymers

56 Pages·2014·2.03 MB·English

by  Pirita Rämänen

Laboratory of Polymer Chemistry
Department of Chemistry
University of Helsinki
Helsinki, Finland

TALL OIL FATTY ACID-BASED ALKYD-
ACRYLIC COPOLYMERS:
SYNTHESIS, CHARACTERIZATION, AND UTILIZATION IN
SURFACE COATING APPLICATIONS

Pirita Rämänen

ACADEMIC DISSERTATION
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

To be presented, with the permission of the Faculty of Science of
the University of Helsinki, for public criticism in Auditorium A110 of the Department
of Chemistry, on November 28th 2014, at 12 o’clock.

Helsinki 2014
Supervisor

Professor Sirkka Liisa Maunu
Laboratory of Polymer Chemistry
Department of Chemistry
University of Helsinki
Finland

Opponent

Professor Mats Johansson
Department of Fibre and Polymer Technology
School of Chemical Science and Engineering
Royal Institute of Technology
Sweden

Reviewers

Professor Maija Tenkanen
Department of Food and Environmental Sciences
University of Helsinki
Finland

&

Professor Eduardo Garcia-Verdugo
Department of Inorganic and Organic Chemistry
Universitat Jaume I
Spain

ISBN 978-951-51-0462-5 (paperback)
ISBN 978-951-51-0463-2 (PDF)
http://ethesis.helsinki.fi

Unigrafia
Helsinki 2014
ABSTRACT
Due to increased awareness of environmental issues and tightened
legislation, bio-based substitutes for traditional petroleum-based polymers
are being increasingly sought. Tall oil fatty acid (TOFA) is an attractive
material for that purpose being a by-product of kraft pulping. Thus, it is
abundant year-round, the price is reasonable, and it does not compete with
foodstuff materials.
In this study, the preparation and properties of TOFA-based waterborne
materials for various coating and barrier applications were examined. Alkyd-
acrylic copolymers were synthesized from conjugated and nonconjugated
fatty acid-based alkyd resins, as well from rapeseed oil-based alkyd resins for
comparison. The polymerization was performed in a miniemulsion, because
of the stability and copolymer formation issues. The ratio between the alkyd
resin and acrylate monomers was varied and the effect on copolymerization
and the copolymer binder properties, such as monomer conversion and
grafting of acrylate to the alkyd resin was studied. It was observed that the
monomers butyl acrylate (BA) and methyl methacrylate (MMA) showed
dissimilar affinity for the grafting site. The steric hindrances prevented MMA
from reacting with the double bonds of the fatty acids as readily as BA. The
allylic, especially the bis-allylic sites, were the principal grafting sites of
MMA, for energetic reasons. However, this effectively retarded the
polymerization and increased the homopolymerization of the acrylates.
Limiting monomer conversion was overcome, using post-initiation.
This research showed that it is possible to prepare stable dispersions of
TOFA-based alkyd-acrylate copolymers with varied chemical composition.
Self-standing films of these dispersions can be prepared and the dispersions
applied effortlessly on paperboard and utilized as barrier material. An
increased amount of alkyd resin made the copolymer films more brittle and
increased their hydrophobicity. Oxygen barrier performance of the materials
was not adequate, but was improved with cellulose. Various cellulose types
were modified with TOFA to improve the compatibility between cellulose and
polymer matrix. Modified cellulose was added to the copolymer dispersion to
improve the mechanical and barrier performance of the copolymer films and
coatings. Enhanced strength as well as increased oxygen barrier properties
were clearly observed when cellulose was used as filler. The water barrier of
the coatings was favorable despite the material composition.
ACKNOWLEDGEMENTS
This research was carried out in the Laboratory of Polymer Chemistry,
University of Helsinki, during the years 2005-2014 under the supervision of
Professor Sirkka Liisa Maunu. The work was carried out mainly in Finnish
BioEconomy Cluster’s (FIBIC) Future Biorefinery (FuBio) research
programme. Finnish Funding Agency for Technology and Innovations
(TEKES) and Graduate School of Natural Polymers (Luonnonpolymeerien
tutkijakoulu) are gratefully acknowledged for funding this research.
I wish to express my deepest gratitude to my supervisor Professor Sirkka
Liisa Maunu for giving me the opportunity to participate in interesting
research projects and for her guidance, encouragement, and patience during
these years. I am also very thankful for Professor Heikki Tenhu, the head of
the Laboratory of Polymer Chemistry, for creating a pleasant atmosphere in
the lab.
I thank Professor Maija Tenkanen and Professor Eduardo Garcia-Verdugo
for reviewing this thesis and their valuable comments.
I would like to thank my collaborators at VTT Technical Research Center
of Finland for making the cooperation in these projects enjoyable. I thank
Pauliina Pitkänen, Dr. Martta Asikainen, Saila Jämsä, Nina Leppävuori, and
Dr. Salme Koskimies for fruitful discussions and providing the alkyd resins,
and Soili Takala for performing numerous applications and measurements. I
am grateful to Dr. Leena-Sisko Johansson at Aalto University for the XPS
measurements.
I thank Dr. Sami Hietala, Dr. Vladimir Aseyev, Seija Lemettinen, Juha
Solasaari, and Ennio Zuccaro for their kind and valuable help whenever
needed. I would like to thank all the members, past and present, of the
Laboratory of Polymer Chemistry. Without you the laboratory would not
have been such a nice place to work in. Special thanks go to Tommi for his
help and patience relating to NMR issues, Pekka for assistance with the
synthesis work, and Joonas for all the help and substituting for me at the
important moment.
Finally, warmest thanks go to my parents, siblings, and friends for all the
support they have given me during these years. My dear husband, Juha,
without you I would not be here. Thank you for all your love, encouragement,
and patience. My little sweetie, Silja, you didn’t make this easier, but showed
the meaning of life.
CONTENTS
Abstract ....................................................................................................................... 3
Acknowledgements .................................................................................................... 4
Contents ...................................................................................................................... 5
List of original publications ...................................................................................... 7
Abbreviations and symbols ....................................................................................... 8
1 Introduction .................................................................................................... 10
1.1 Background ............................................................................................ 10
1.2 Alkyd resin ............................................................................................... 11
1.3 Alkyd-acrylic copolymers ...................................................................... 13
1.4 The drying process ................................................................................. 16
1.5 Barrier dispersions ................................................................................ 18
1.6 Objectives of this study.......................................................................... 20
2 Experimental ................................................................................................... 21
2.1 Materials ................................................................................................. 21
2.1.1 Synthesis of copolymers ..................................................................... 21
2.1.2 Celluloses used as fillers ..................................................................... 24
2.1.3 Films and coatings .............................................................................. 25
2.2 Characterization ..................................................................................... 25
3 Results and discussion ................................................................................... 27
3.1 Alkyd resin structureII ........................................................................... 27
3.2 Alkyd-acrylate copolymers .................................................................... 29
3.2.1 ConversionI,III ...................................................................................... 29
3.2.2 Particle sizeI ......................................................................................... 31
3.2.3 Acrylic degree of grafting and grafting sites in alkyd resinI-III ........ 32
3.2.4 Thermal propertiesI,III ........................................................................ 36
3.3 Surface modification of celluloseIV ...................................................... 38
3.3.1 Surface modification .......................................................................... 38
3.3.2 Degree of substitution ........................................................................ 40
3.4 Film properties ....................................................................................... 41
3.4.1 Oxidative dryingI,II ............................................................................. 42
3.4.2 Mechanical propertiesIII .................................................................... 42
3.4.3 Barrier propertiesIII, unpublished data ........................................................45
3.4.4 Effect of celluloseunpublished data ........................................................... 46
3.4.5 Applications ........................................................................................ 48
4 Conclusions ..................................................................................................... 50
5 References ........................................................................................................ 52
LIST OF ORIGINAL PUBLICATIONS
This thesis is based on the following publications. Some unpublished
material is also presented.

I Uschanov, P.; Heiskanen, N.; Mononen, P.; Maunu, S. L.;
Koskimies, S. Synthesis and characterization of tall oil
fatty acids-based alkyd resins and alkyd-acrylate
copolymers. Prog. Org. Coat., 2008, 63, 92-99.

II Rämänen, P.; Maunu, S.L. Structure of tall oil fatty acid–
based alkyd resins and alkyd-acrylic copolymers
studied by NMR spectroscopy. Prog. Org. Coat., 2014, 77,
361-368.

III Rämänen, P.; Pitkänen, P.; Jämsä, S.; Maunu, S. L. Natural oil
based alkyd-acrylate copolymers: New candidates for
barrier materials. J. Polym. Environ., 2012, 20, 950-958.

IV Uschanov, P.; Johansson, L.-S.; Maunu, S. L.; Laine, J.
Heterogeneous modification of various celluloses with
fatty acids. Cellulose, 2011, 18, 393-404.

The publications are referred to in the text by their Roman numerals.

Author’s contribution to the publications:
Pirita Rämänen (née Uschanov) was responsible for the synthesis and
characterization of the copolymers, drew up the research plan, and wrote the
manuscript in close collaboration with the coauthors (I,III). The author
independently drew up the research plan, was the first author, and wrote the
manuscripts in close collaboration with the coauthors (II,IV).

In addition, the author contributed to a publication that is directly related to
this thesis:

Rämänen, P.; Penttilä, P. A.; Svedström, K.; Maunu, S. L.; Serimaa, R. The
effect of drying method on the properties and nanoscale structure
of cellulose whiskers. Cellulose, 2012, 19, 901-912.

7
ABBREVIATIONS AND SYMBOLS
ADG Acrylic degree of grafting
BA Butyl acrylate
CPMAS Cross polarization magic angle spinning
CTO Crude tall oil
DB Double bond
DECA Decanoic acid
DLS Dynamic light scattering
DMA Dynamic mechanical analysis
DSC Differential scanning calorimeter
DS Degree of substitution
FTIR Fourier transform infrared spectroscopy
GMA Glycidyl methacrylate
HD Hexadecane
HMBC Heteronuclear multiple-bond correlation
HSQC Heteronuclear single quantum correlation
IPA Isophthalic acid
IV Iodine value
KOH Potassium hydroxide
KPS Potassium persulfate
LINA Linoleic acid
MCC Microcrystalline cellulose
MFC Microfibrillated cellulose
MMA Methyl methacrylate
NMR Nuclear magnetic resonance
O/C Oxygen/carbon ratio
OH Hydroxyl
OLA Oleic acid
OTR Oxygen transmission rate
PE Pentaerythritol
PINA Pinolenic acid
RegCell Regenerated cellulose
RH Relative humidity
RO Rapeseed oil
RT Room temperature
SDS Sodium dodecyl sulfate
SEC Size exclusion chromatography
ssNMR Solid-state NMR
TAN Total acid number
TGA Thermogravimetric analysis
THF Tetrahydrofurane
TMP Trimethylol propane
8
TOFA Tall oil fatty acid
TsCl p-Toluene sulfonyl chloride
VOC Volatile organic compound
W-TOFA TOFA-modified cellulose whiskers
WVTR Water vapor transmission rate
XPS X-ray photoelectron spectroscopy

Cobb Cobb test for 1800 s
1800
DH° Bond dissociation energy
G’ Storage modulus
G’’ Loss modulus
T Glass transition temperature
g
T Onset temperature
onset
wt% Weight percent

9
Introduction

1 INTRODUCTION
1.1 Background
Environmental issues have risen to the forefront in matters pertaining to
materials and their applications. Surface coating materials are no exception.
Surface coating is a general description for any material that can be applied
as a continuous film to a surface; so it can be claimed that coatings are
present everywhere in our daily lives. Coatings are usually associated with
paints, but they can also be used for decoration, protection, and some
functional purposes. Some examples of applications include architectural
coatings, such as paints and varnishes, which are used to decorate and
protect buildings. The coating inside a food package protects the content of
the package, but also furnishes protection for the package from the content.
Special functions of coatings include preventing the growth of algae on ships,
retarding corrosion on steel products, functioning as flame retardant on
fabrics, or serving as recording media on compact discs.1,2 Overall, coatings
aim at enhancing the durability of products apart from their aesthetic
function. A considerable amount of research is in progress, just to find new
materials to replace existing petroleum-based materials. Today’s world is
placing high demands on the performance of coating materials: in addition to
the functional properties, sustainability, cost, environment, safety, and
health aspects are high on the priority list.3
Vegetable oils have been used in coatings for over 600 years and they still
play an important role, due to their versatility and availability as renewable
resources.1,2 Alkyd resins were developed to combine vegetable oils into
polyester structures, enhanced properties were gained, and alkyds became
hugely successful in the paint industry. However, the development of new
thermoplastic polymers diminished the value of alkyd resins in the paint
industry during the 1950s. The main reason was the environmental aspect;
the new coating materials were waterborne latexes and contained fewer
volatile organic compounds (VOCs) than did alkyd resins.
In recent decades, various ways of producing more environmentally
friendly alkyd resins have been examined to increase the attractiveness of
alkyds in the coating field to their former level. Alkyd emulsions, high-solid
content alkyds, and modified alkyds have played a major role in the
resurgence of alkyd resins. They are more environmentally friendly versions
of alkyd resins that satisfy ecolabeling requirements.1,4 Nevertheless, the
advantages of solventborne compared with waterborne materials include
easier application, reduced sensitivity to surrounding conditions, and good
adhesion to various substrates, reasons why they are still on the market and
in use and probably cannot be replaced completely. Moreover, waterborne
coatings may show problems with their relatively high surfactant
10