The Role of Thickeners in Optimising Coatings Formulation

Transcription

1 The Role of Thickeners in Optimising Coatings Formulation Clemens Auschra, Immanuel Willerich, Iván García Romero, Hunter He, Robert Reichardt, Cindy Muenzenberg, Elena Martinez ChinaCoat, December

2 Outline Rheology in waterborne coatings Influence of rheology modifiers and latex binder Interior paints: comparison of different rheology modifiers Rheology modifiers: new developments Outlook 2

3 Importance of rheology on paint application Brookfield Stormer ICI Controlled Stress Rheometer 3

4 High PVC paint: typical composition ~35% ~18% Binder Fillers Water TiO 2 ~10% paint rheology is influenced by many components: main influence by: rheology modifier, latex, pigments & their interactions 4

5 Theory: Rheology of disperse systems Hard sphere models liquid particle interactions Ideal suspension - low concentration - uniform spheres - no interactions particles: latex, fillers, pigments Real suspensions - different particles, size, shape,.. - high concentration - with interactions η r = η suspension η liquid = Φ (Φ = volume fraction particles) η r = η suspension = Φ + KΦ 2 η liquid. Paint: -> effective volume fraction Φ eff of latex influenced by surface chemistry -> interaction between particles + interaction with additives: associative rheology modifiers, dispersants, surfactants 5

6 Polymer Binders Benchmark dispersion polymer binders used in this study Binder Region Chemistry Solids Particle Size (DLS) MFFT Remark SA-1 Asia styrene / acrylate 50% 158 nm ~16 C excellent water resistance & hydrolytic stability SA-2 Asia styrene / acrylate 48% 148 nm ~24 C excellent scrub resistance AC-3 NAFTA all acrylic 50% 126 nm ~10 C AC-4 Europe all acrylic 50% 198 nm ~2 C suitable for zero VOC paints excellent cleanability suitable for low VOC paints broad formulation latitude 6

7 Rheology of pure binders pure 40% solids, ph = 8.5 Viscosity [mpas] binder SA-2 binder AC-4 binder AC-3 binder SA-1 Binder Chemistry Particle size Pseudoplasticity Index η (0.1 s-1) / η (1000 s-1) SA-2 styrene / acrylate 148 nm 12.4 AC-4 all acrylic 198 nm 4.2 AC-3 all acrylic 126 nm 2.6 SA-1 styrene / acrylate 158 nm Shear rate [1/s] No simple correlation to latex monomer chemistry or particle size latex SA-2 with higher hydrodynamic effective volume fraction: Φ eff 7

8 Rheology modifiers Three different classes studied HASE Alkali-soluble backbone CO 2 H CO 2 H CO 2 H CO 2 H HEUR Hydrophilic backbone Associative Hydrophobes ASE Non-Associative COO- COO- COOformulation: ph > 7 emulsion: ph <5 8

9 Rheology Modifiers Benchmark low shear rheology modifiers used in this study Rheology Modifier Chemistry Product form ph Solids Viscosity (mpas) HASE associative anionic polyacrylate (hydrophobe modified alkali swellable emulsion copolymer) aqueous emulsion ~3.5 35% ~5 HEUR associative nonionic polyurethane (hydrophobe modified polyethyleneoxide urethane copolymer) aqueous solution ~7 30% ~2700 ASE anionic polyacrylate (alkali swellable emulsion copolymer) aqueous emulsion ~3.5 30% ~40 9

10 Binary system: latex (40%) + rheology modifier (0.28%) Low shear thickening efficiency Thickening Efficiency : TE = η (Latex + Rheology Modifier) η (pure Latex) Different response depending on latex type HASE most efficient 10

11 Binary system: latex (40%) + rheology modifier (0.28%) Impact on low shear and high shear viscosity HASE most efficient HEUR more balanced ASE more pseudoplastic 11

12 Associative rheology modifiers Thickening mechanism of HEUR How to study the interaction between colloid particles and the rheology modifier? 12

13 Interactions between latex and rheology modifier Study be electrophoretic mobility: e.g. HEUR low Mobility high Latex AC-4 shows weaker interactions to HEUR 13

14 Binary system: latex (40%) + rheology modifier (0.28%) Thickening response of different latex versus HEUR SA-2 SA-1 AC-3 SA-2 AC-4 AC-3 SA-1 AC-4 Latex AC-4: relative low thickening with HEUR Good response with all other binders 14

15 White base paints used for testing of rheology modifiers Paint A interior matt PVC = 68% Paint B interior matt PVC = 80% Paint C gloss paint PVC = 18% Paint D interior matt PVC = 68% from region Asia Asia NAFTA Europe main binder SA-1 SA-2 AC-3 AC-4 rheology modifier in base paint no cellulosic HEC no cellulosic HEC preferred rheology modifier HEUR HEUR HEUR-1 (KU) HEUR-2 (ICI) / 15

16 Base paints + same active content rheology modifier (0.175%) Comparison: low shear thickening efficiency Thickening Efficiency : TE = η (Paint + Rheology Modifier) η (pure Base Paint) HASE: most efficient HEUR: balanced efficiency Paint D with lowest response 16

17 Base paints + same active content rheology modifier (0.175%) Comparison: overall thickening response different response by each base paint Paint D with lowest response 17

18 Rheology of paints: comparison paint A versus paint B Paints adjusted with rheology modifier to KU = 100 Viscosity [mpas] paint A HASE HEUR ASE base paint A w/o RM Viscosity [mpas] paint B HASE HEUR ASE base paint B w/o RM Shear rate [1/s] Shear rate [1/s] Low shear thickening: HASE > ASE > HEUR HEUR: more newtonian, more balanced 18

19 Paint B: application properties versus rheology Paints adjusted with rheology modifier to KU = 100 Rheology Modifier low shear thickening 0.1 s-1 Pseudoplasticity index Sagging Test Levelling Test η (0.1s-1) / η (1000s-1) HASE no sagging poor HEUR no sagging good levelling ASE no sagging poor Sagging Test Levelling Test base paint B + HEUR base paint B + HEUR 19

20 Dynamic mechanical analysis Paint B: adjusted with rheology modifier to KU = 100 strain 10 rad/s 1000 G' and G" [Pa] base HEUR ASE HASE paint Strain Amplitude Crossover points correlate to levelling performance 20

21 Development of new nonionic rheology modifiers Novel concept: branched and hyperbranched polymer structures HEUR New concepts Hydrophilic backbone Hydrophobes New hydrophobe structures with optimum interaction to latex surface Branched polymer architectures: backbone a/o hydrophobes 21

22 New nonionic rheology modifiers Comparison: linear versus hyperbranched HEUR 0.25% thickener actives in a pure acrylic dispersion Hyperbranched end groups + high molecular weight: -> significant improved thickening 22

23 New hyperbranched HEUR Testing in high PVC pure acrylic paint Properties HEUR 2 Hyper-branched, high molecular weight Hyper-branched, low molecular weight Viscosity [mpa*s] Active [%] Flow & Levelling Sag [mm] Target viscosity: 1700 mpa.s [Brookfield viscosity] Flow & leveling: 0.25 = excellent, >4.0mm = bad Sag: 300µm = excellent, 75µm = bad -> significant improved thickening efficiency -> no compromise in levelling & sag behavior 23

24 Summary & Outlook Binary model systems: Interaction between latex and rheology modifiers were studied by rheology and correlated to electrophoretic mobility Optimum thickener response results with good fit of hydrophobe chemistry to latex surface Paints: Fully formulated paints show similar trends concerning different classes of rheology modifiers New rheology modifiers: Results from model studies help to design new associative thickeners with optimum response towards new generation latex binders New hyperbranched HEUR with high efficiency 24

25 Formulation Additives 2525