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Aqueous Dispersions from Aqueous Dispersions from Biodegradable/Renewable PolymersBiodegradable/Renewable Polymers
M. Vähä-Nissi a, C. Laine a, R. Talja a, H. Mikkonen b, S. Hyvärinen b, A. Harlin a
Technical Research Centre of Finland , Espoo a/Rajamäki, b, Finland
Who are we?Who are we?
Provide high-end technology solutions and innovation servicesStaff: 2900 experts, turnover 280 Million €Combined with former KCL’s resources
Outline of presentationOutline of presentation
Introduction and motivation:Biodegradable and natural polymers
Pseudo dispersions – preparation and key properties
Experimental details:Materials and methods
Case studies:Renewable hemicellulose dispersions
Biopolymer dispersions as replacement of synthetic binders
Biopolymer dispersions as barrier coatings
Conclusions
INTRODUCTION AND INTRODUCTION AND MOTIVATIONMOTIVATION
Biopolymers and pseudo dispersions
Spray-dried PHB granulesLauzier et al., TAPPI J., 1993
5
BIOPOLYMERS
Extracted from biomass
Polysaccharides Starch, cellulose, hemicelluloses, pectins, gums,
chitosan, etc. and derivatives
Proteins
Plant - zein, soya, gluten
Animal - casein, whey, collagen
Lipids Cross-linked tri-glyceride Polylactic
acid (PLA) & copolymers
Polyhydroxyalkaonates (PHA)
Polyhydroxybutyrate(P
HB)
Polyhydroxyvalerate
(PHV)
Polyhydroxyhexanoate(PH
H)
Bacterial cellulose,
etc.
Copolymers
Polymers produced by organisms
Bio-derived polymers
Synthetic non-renewables
Polysuccinates(PESU
, PBS, PB
SA)
Polycaprolactone(PC
L)
Modified PET
Aliphatic-A
romatic copolyester
From renewables
Dispersion from biopolymers Dispersion from biopolymers –– why?why?
Thin coatings possible
Blends/multilayered struct. for adhesion not needed
Alternative application techniques for biopolymers
More freedom for formulation (additives, fillers)
Dispersions today based on synthetic polymers poorly degraded in a biological environment
Taxation in central Europe - monomaterial recycling (and composting in future!)
Decreased dependency on oil availability and price
Everyone looking for ”green” alternatives
Preparing biopolymer dispersionsPreparing biopolymer dispersions
Emulsion polymerizationTypically water soluble (& insoluble) mono- and oligomersPatents on starch grafted synthetic polymer and polyesters dispersionsBetter control on particle size, particle polymer composition
Pseudo dispersionsFor preformed, insoluble polymers not suitable for emulsion polymerizationVolatile organic solvent –based and thermo/ mechanical methodsUsed for both synthetic polymers and biopolymers. Feasibility depends very much on polymer.
Pseudo biodispersions Pseudo biodispersions -- TechniquesTechniques
Volatile organic solvents:Emulsification-evaporationPrecipitationSalting-outEmulsification-diffusion
Mixing and finding suitable polymer/solvent/stabilizer system crucialCosts, safety, leak-prevention, removing/recovering solventNo thermal stresses
Thermo/mechanical:Thermal treatmentMelt dispersingPremixture – heating – dilutionReactive extrusion
Adjusting morphology of particles (semicrystalline polymers)Using heat or low non-volatile solvents (plasticizer)Thermal stability
Often different combinations used!
Key dispersion propertiesKey dispersion properties
Pigment coating binder:Binding power to pigments and substrates”Spot welding” at temperatures typical during drying (65-80 °C).Low high shear viscosity and high water retentionPrintability (surface strenght, coating structure, etc.)Traditionally ”few good men”
Barrier dispersion:Uniform pinhole free layerFilm formation (MFFT)Inter-diffusion of molecules accross particle borders (neutralizing, additives)Low monomer residuesTraditionally more emphasis on environmental issues?Synergy with specialties
In both cases stable dispersions with high solids and small particle size compatible with other ingredients
EXPERIMENTAL DETAILSEXPERIMENTAL DETAILS
Materials and MethodsMaterials and Methods
Biopolymers:PolyhydroxyalkaonatesPolylactide-based polymersPolycaprolactonePolybutylenesuccinate/adipateNanoparticle starchXylan from bleached pulp
References:Synthetic dispersionsCooked starch
Substrates:LWC –base paperCupboardPolymer film
Coating:
Analyses:Particle size, stabilityViscosity, water retentionWater absorption, WVTROptical properties, strength
RENEWABLE HEMICELLULOSE RENEWABLE HEMICELLULOSE DISPERSIONSDISPERSIONS
Little utilized abundant group of natural polymers
Why hemicelluloses?Why hemicelluloses?
3 x 1010 tons of hemicelluloses photosynthetized each year by plants making them 2nd most common natural polymer.No serious competitive end-uses today; limited use as raw-material for production of fine chemicals.In pulping hemicelluloses partly precipitate on fibers after cooking and partly leached into the cooking liquor of alkaline cooking and combusted. Low calometric value of hemicelluloses favors alternative end-uses.Different hemicelluloses obtained from different plants and processes allow selective production and utilization.Similarly to other polysaccharides they can be modified
13
Hemicellulose dispersions Hemicellulose dispersions
Possibility to high solids Water insoluble polymers and hydrophobic derivatives –dispersion through e.g. alkanoic acidFilm formation affected by Tg, particle size, etc. Possible to apply internal plasticization (etherification and/or esterification, etc.) - no migration or chrystallization of plasticizers.Stability
14
Xylan acetate dispersion
Dispersions from birch xylanDispersions from birch xylanXylan extracted from bleached birch pulp:
Hydroxypropylation (US5430142)
Acetylation
Acetylation in acetic acid/anhydride (FI20075399 )
Dispersing & stability, lower Tg
Insoluble in water and common solvents
Modification mattersModification mattersXy
lan
disp
ersi
on
Hyd
roxy
prop
. xyl
an
Hyd
roxy
prop
. &
acet
ylat
ed x
ylan
Dis
p. o
f xy
lan
deriv
.
BIOPOLYMER DISPERSIONS BIOPOLYMER DISPERSIONS AS REPLACEMENT OF AS REPLACEMENT OF SYNTHETIC BINDERSSYNTHETIC BINDERS
Sustainable alternatives to oil-based binders in pigment coatings
PHA, PLA and starch dispersionsPHA, PLA and starch dispersions
PHA dispersion, premixture followed by heating and diluting in water, 44%
PLA dispersion, dissolved in THF & precipitated in water, 20%
Nanoparticle starch powder added to pigment slurry 30 min of mixing
Small effect on optical propertiesSmall effect on optical properties
45
55
65
75
85
%
Brightness Light‐scattering
PHA and PLA biodispersion
Low replacement levels okLow replacement levels ok
0
1
2
3
4
5
6
10L 2.5PLA/7.5L 5PLA/5L 10L 5PHA/5L
Picking (*0,1 m/s) Passes to pick
PHA and PLA biodispersion
Slight effect on optical propertiesSlight effect on optical properties
55
60
65
70
75
80
85
%
Brightness Gloss
Biodispersion from starch
Acceptable dry and wet strengthAcceptable dry and wet strength
01234567
Picking (*0.1 m/s) Passes to pick
Biodispersion from starch
BIOPOLYMER DISPERSIONS BIOPOLYMER DISPERSIONS AS BARRIER COATINGSAS BARRIER COATINGS
Expanding potential of biodegradable dispersions
Biodispersions from PLA, PHA and PCLBiodispersions from PLA, PHA and PCL
Solubility of different biopolymers checked in advance.Dispersions from PLA 2 with precipitation, PCL (I) with emulsion/evaporation and PHA 5 with dispersing agent.Dispersions milky white and stable at least for 1-2 weeks.Process temperature low to avoid agglomeration
PHA 5 dispersion with solid contents of 50%.
Polymer Additives Solid contents Stability Method PLA 2 - 20% Good Precipitation PCL (I) PVA 44.9% Good Emul./evap. PCL (II) - 4.2% Flocks Precipitation PBSA Tween21, PVA 13.3% Stable Emul./evap. PHA 2 - 4.5% Stable Precipitation
Particle size distribution widerParticle size distribution wider
0
0,2
0,4
0,6
0,8
1
0 200 400 600 800 1000
Cumulative nu
mber
Particle diameter ‐ nm
Ref. PLA 2 PCL (I) PHA 5*
PCL - highest portion of big particles partly due to process*PHA – visually 2 types of particles (chrystalline/amorphous?)
Properties of films & coated boardsProperties of films & coated boards
PLA good water barrier, but requires relatively high Tdrying .PCL (I) dispersion quite good water vapor barrier.PHA 5 requires more work for improved film formation.
Larger samples required for optimizing coating color and coating/drying parameters.
Water sorption (1 and 10 min) into films Cobb 10 min (g/m2) and WVTR - 23°C, 50% (g/d/m2) of dispersion coated (10 g/m2) board
Reference dried at 80 °C: 2 and 3% PCL (I) dried at 80 °C: 35 and 34 % PCL (I) dried at 105 °C: 41 and 35% PLA 2 dried at 175 °C: 0.6 and 0.9% PLA 2 dried at 200 °C: 0.7 and 0.8%
Reference dried at 105 °C: 4.4 and 110 PCL (I) dried at 105 °C: 56 and 59 PCL (I) dried at 140 °C: 55 and 64 PHA 5 dried at 140 °C: 64 and 446 PHA 5 dried at 160 °C: 73 and 461
ConclusionsConclusions
Methods for preparing dispersions from biopolymers exists. these can be roughly divided into volatile organic solvent based and thermo/mechanical techniques. However, feasibility of specific biopolymer for certain process has to be evaluated carefully.Dispersions of relatively high solids and good stability were prepared both from typical biodegradable polymers, such as PLA, PHA and PCL, and from polysaccharides, such as starch and xylan. Dispersions had specific properties making them interesting in future as possible total or partial replacement of synthetic dispersions in coatings.
AcknowledgementsAcknowledgements
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Presented by:
Mika Vähä-Nissi