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