High performance Acrylic Dispersions for Masonry and Wood Coatings

26 Pages·2015·1.26 MB·English

by  Achim Bräunlich

High performance Acrylic Dispersions
for Masonry and Wood Coatings
Harald Petri , Ulrich Désor , Dr. Matthias Junk
© Celanese ASEFAPI, 5th November 2015
Agenda
► Polymer Dispersions – Basic Knowledge

► Homogeneous Acrylic Dispersions

► Advanced Polymerization Technologies
‒ Core/Shell -Technology
‒ New Gradual Composition (GC) –Technology from Celanese

► Application Test Results

► Summary

© Celanese High performance Acrylic Dispersions 2
What is a Polymer Emulsion ?
( in fact : Polymer Dispersion )
Synonym
Water

Homogeneous Medium
Polymer-Dispersion

Polymer Colloid

Polymer Particle
Latex
Heterogeneous Medium
„Polymer-Emulsion“
A polymer dispersion consists of very small polymer particles
distributed in the homogeneous phase water
© Celanese High performance Acrylic Dispersions 3
Structure of a polymer particle
Polymer Properties
- chemical composition
- glass transition temperature (Tg)
- degree of crosslinking
- molecular weight
Colloidal Properties
- emulsifier, type, amount
- number of sphere charges
- number of charges in serum
A polymer particle is composed of a „polymer core“ and a
colloidal „shell“ which has a strong impact on workability
© Celanese High performance Acrylic Dispersions 4
Film formation
Phase I Evaporation of water
Proper film
formation only
Phase II Deformation of particles
occurs if ambient
temperature is
above MFFT !
Phase III Coalescence
Phase IV Interdiffusion of polymer chains
Proper film formation needed to obtain a robust polymer film
© Celanese High performance Acrylic Dispersions 5
Film formation
Minimum Film Formation Temperature ( MFTT )
0°C Temperature Gradient 20°C
MFFT 0°C
18°C
>20°C
MFFT – Bench
The Minimum Film Formation Temperature ( MFFT ) is the lowest
temperature required to obtain a polymer film without any defects.
MFFT can vary from 0°C ( freezing water ) to 100°C ( boiling water )
!
© Celanese High performance Acrylic Dispersions 6
Polymer hardness
Glass Transition Temperature ( Tg )
Tg of Polymer Film
100 oC 25 oC -100 oC
stiff and briddle leather-like tacky

Plastic Coatings Masonry Coatings EWC

( Pure Acrylic ; Tg = 98°C ) ( Pure Acrylic ; Tg = 23°C ) ( Pure Acrylic ; Tg = -30°C )

Fibre Cement Coatings Masonry Coatings
( Pure Acrylic ; Tg = 48°C ) - low emission -
( Pure Acrylic; Tg = 6°C )
below Tg : Polymer chains like above Tg : Polymer chains like
uncooked Spaghetti ( rigid ) cooked Spaghetti ( flexible )
© Celanese High performance Acrylic Dispersions 7
Correlation between MFFT and Tg
30
25

)
C
° 20
(
Tg = MFFT Styrene-Acrylic
T
15
F
F
M 10
VAE
5
0
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
T (°C)
g
 MFFT correlates with Tg in many cases, but is not the same.
 Tg ≈ MFFT for hydrophobic polymers ( e.g. Styrene/Acrylic ).
 MFFT can be lowered by adding suitable solvents and/or coalescing agents.
 For hydrophilic polymers ( e.g. VAE ) water can act as coalescing agent
( Hydroplastification ).
 Heterogeneous dispersions could have more than one Tg whereas every dispersions
has only one MFFT.
© Celanese High performance Acrylic Dispersions 8
Film Forming Process of homogenous
Polymer Dispersions ( „soft “ vs. „hard“ )
Lowering of MFFT by
adding suitable
coalescent agents
MFFT /Tg
Production
[ °C ]
Hard Polymer Film
40
‘hard’ Evaporation of
Dispersion coalescent
agents
30 Addition of
coalescent
agents
20
typical ambient
Application
Drying
‘soft’ temperature
10
Storage
Dispersion
Soft Polymer Film
0
time
© Celanese High performance Acrylic Dispersions 99
Combining opposing properties
Film forming without any addition of To achieve a better polymer hard-
?
coalescent agents requires a “soft” ness ( low blocking ) especially at
polymer dispersion and thereby a high temperatures “hard” polymer
relative soft polymer film hardness. dispersions are required.
Low Glass Transition High Glass Transition
Temperature (Tg) Temperature (Tg)
Advanced Polymerization Technologies – Best of both worlds
Optimizing the balance between Soft Polymer Phase
( low Tg ) and Hard Polymer Phase ( high Tg ).

Soft phase enables the film forming at lower
temperatures and reduced demand of coalescing
agents whereas the high Tg phase improves film
hardness and block resistance.
© Celanese High performance Acrylic Dispersions 10