Automotive coatings Improving efficiency, enhancing aesthetics Eastman cellulose esters ADD-COAT-7954
Agenda Cellulose esters overview Desired attributes for automotive coatings Improving application and appearance Cellulose esters in basecoats Conventional low/medium solids solventborne basecoats Higher solids solventborne basecoats Cellulose esters in clear and top coats High solids clear coats
Introduction to cellulose esters Eastman supplies free flowing powders Produced from renewable sustainable raw materials CAB/CAP solution Eastman cellulose esters come from renewable sources and have unique properties that enhance the application and aesthetics of automotive coatings
Cellulose esters A product of the reaction between organic acids and anhydrides with cellulose: Acetic acid/anhydride Butyric acid/anhydride Propionic acid/anhydride Cellulose acetate (CA) Cellulose acetate butyrate (CAB) Cellulose acetate propionate (CAP) Eastman cellulose esters are available in a wide variety of formats and dispersions for versatility in use to achieve desired formulation and coatings attributes.
Code designation Example Eastman cellulose acetate butyrate - - CAB 38 1 0.1 Cellulose acetate butyrate Approximate butyrl content at trimester stage (wt%) Falling-ball viscosity (s) Number of OH-groups per four anhydroglucose units Use solubility and molecular weight details for effective formulation and solvent choices
Chain packing CA vs. CAB Acetate molecule Butyrate molecule Understanding chain packing impacts solubility parameters and solvent choice
Eastman cellulose esters for coatings application R1,R2,R3 Acetyl, butyryl/propyl or H Pharmaceutical and other products Cellulose acetate Cellulose acetate propionate Cellulose acetate butyrate Automotive coatings: Cellulose esters enable high quality, compliant systems with higher solids
Segment Overview
Needs in automotive applications Improving application and aesthetics Automotive OEM needs Flow and leveling (gloss/smoothness) Metallic flake alignment (brightness) Reduced drying time (throughput) Automotive refinish needs Improved atomization (uniformity) Reduced surface defects (1 st pass yield) Rheology (application and appearance)
Metallic basecoats Details and desired attributes Designers use metallic paint and special effect pigments to enhance flow lines in body panels and other components. Metallic basecoats allow the use of a mixture of materials on a vehicle which all have the same appearance. Body coloured plastic components bumpers, wing mirrors, and more. Coated alloy wheels or plastic wheel trims Coated plastic components are generally cheaper, lighter, and more versatile than using actual metal components. Coatings can be given different tactile qualities such as soft feel and visual effects such as matt/glossy appearance. Consistent appearance across all vehicle components is crucial and can be impacted by ingredient and formulation choices
Segment Challenges Addressed by CAB and CAP
How CAB functions in metallic basecoats Viscosity of CAB permits application of heavy basecoat Aluminum pigment (flakes) As solvent evaporates, film shrinks, flake orientation begins Clear coat CAB prevents solvents in clear topcoat from redissolving basecoat
Solution viscosity With CAB No CAB Solution viscosity V T 1 Time T 2 With CAB, solution viscosity increases more rapidly
Comparing metallic flake orientation Coatings with and without CAB With Eastman CAB viscosity changes more quickly, allowing for better metallic flake orientation at the right time of the drying process Without Eastman CAB metallic flake orientation is hindered based on less desirable viscosity during drying
Improved flake orientation Indications of ideal flip flop 90 Highest coating brightness at direct view 45 Coating appears progressively darker at angle view With CAB Without CAB
Tuning the properties of coatings What if Attributes increase Attributes decrease Butyryl content of cellulose esters increases? Hydroxyl content of cellulose esters increases? Cellulose ester viscosity increases? Flexibility Solubility Hydrocarbon tolerance Compatibility Water tolerance Alcohol tolerance Hardness Reactivity Melting point Toughness Chemical resistance Grease resistance Hardness Moisture resistance Alcohol resistance Compatibility (very slightly) Solubility (slightly) Solution nonvolatile at fixed viscosity Cellulose esters are versatile problem solvers that offer formulators many options to achieve desired application and coating attributes
Results for cellulose esters in metallic base coats Conventional solventborne basecoats Solus 2300 in higher solids solventborne basecoats Cellulose esters in clear coat and topcoat systems
Eastman cellulose acetate butyrate for conventional solventborne basecoats
Typical metallic basecoat formulation Component Weight Description Supplier Alpate 7106 NS 61.0 Metallic pigment Toyal Europe Butyl acetate 61.0 Xylene 35.5 Cerafak 106 120.0 Wax Byk-Chemie Setal 90173 SS-50 320.0 Polyester resin Nuplex Resins Dow corning 56 (10%) in butyl acetate) 360.0 Eastman Chemical Company Butyl acetate 35.0 Total 1000.0 Butyl acetate till application viscosity Technical data Property Value Test method Application viscosity at 23 C 16 18 sec DIN cup 4 Solids content 20%
Typical components of a basecoat explained Ingredient Typical amount Function Binder (polyester or acrylic) Cellulose ester 40 60% of total solids 15 35% of total solids Appearance, depth of image (DOI), physical properties Flake orientation, fast drying, prevents re-dissolve by top coat Melamine resin 15 30% of total solids Inter-coat adhesion Polyethylene wax dispersion 5 10% of total solids Helps appearance, reduces mottling Metallic flake (aluminium) 10 15% of total solids Metallic effect, substrate hiding Solvent To application viscosity (20 Sec. DIN 4 flow cup) Fluidity, regulates drying time; solids at application viscosity typically > 20% Additives As needed Flow, levelling
Flake orientation Confocal microscopy Without CAB With CAB With CAB, metallic flakes align flat and reflect more light, enhancing appearance
Visual affect of metallic flake orientation
Resistance to redissolve by clear coat With CAB No color change Without CAB Visual color change CAB in the basecoat allows wet on wet application of clear coat without redissolve, which can alter appearance
Reducing redissolve SEM images of basecoat/clearcoat interphase Without CAB With CAB Diffuse interphase due to solvent migration into the basecoat layer Poorer alignment of Al flakes Clean interphase indicating lower redissolve of the basecoat layer Redissolve can negatively impact appearance
Effect of increasing the level of CAB Delivers enhanced aesthetic properties Improves appearance Smoother, more uniform paint film More consistent metallic flake orientation Improved color consistency
Solus 2300 for higher solid automotive solventborne basecoats
Eastman Solus 2300 performance additive Automotive OEM basecoat performance Generic OEM basecoat formulation Formulation Wt % Formulation/application data Polyester polyol (60% NV) 40.7 Solids as prepared (%) prior to reducing to spray viscosity 46.90 Melamine resin (70% NV) 17.2 Application viscosity (#4 Ford cup), seconds 20.06 Solus 2300 (40% in n-butyl acetate) 9.4 Theoretical solids (%) 39.60 Wax dispersion (5% NV) 19.8 Measured solids (%) at application 39.40 Flow additive 0.7 8.25 Aluminum flake (70% NV) 11.2 Density (g/l) 989 Solvent blend 1.0 Total: 100.0 NV = Non-volatile
Automotive OEM basecoat With Solus 2300 Control Solus 2300 Solus 2300 / microgel Top view Side view Avg RMS : 4.69 um FI : 7.1 Avg RMS = 2.36 um FI : 10.1 Avg RMS = 2.08 um FI : 13.4 With Solus, metallic flakes align flat and reflect more light, enhancing appearance
Eastman Solus 2300 Additional benefits to basecoats Helps in lowering volatile organic compounds (VOC) Superior performance Optimized flake control/face brightness Enhanced distinctness of image (DOI) Reduced dry-to-touch times Improved re-dissolve/strike-in resistance Smoother films Greater productivity by enabling higher solids Reduced defects during and after coatings application
Cellulose esters in clear and top coat systems
Automotive clear coat Desired application and appearance attributes Application Faster dry to touch Improved flow and leveling and sag resistance Improved hardness development Appearance Improved distinctness of image (DOI) Reduced defects
Clear coat formulation 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Acrylic +10% Cellulose ester Solvent Additives Curing agent Cellulose ester Polyol Control Novel approach Acrylic resin (75% n-ba) 58.12 52.30 Solus 2100 (55% MIAK) - 7.92 n-butyl acetate 6.44 7.90 MIAK 5.58 2.02 Catalyst (1% in n-ba) 2.18 2.18 Part A subtotal 72.32 72.32 HDI trimer (90% n-ba) 20.76 19.67 n-butyl acetate 5.67 5.37 PM Acetate 3.72 3.53 Part B subtotal 30.15 28.57 Thinner (n-butyl acetate/1-ethoxy- 4.0 6.0 2-propanol acetate 60/40) Total 106.47 106.89
Enhanced drying performance With Solus 2100 Sand free free dry dry time time (mins) (min) 70 60 50 40 30 20 10 0 15 minute drying time reduction Control Fast Drying drying Acrylic acrylic Fast drying Drying Acrylic acrylic +10% cellulose Cellulose Ester ester Reducing trying time is significant and decreases the chance of airborne contaminants to settle on wet paint and negatively impact appearance
Enhanced sagging performance With Solus 2100 65 Dry film thickness @ sag point (µm) 60 55 50 45 Spray application 40 Fast Drying Acrylic Fast drying acrylic Fast drying acrylic Fast Drying Acrylic +10% cellulose ester +10% Cellulose Ester With Solus, higher Tg and faster solvent release mean top coats can be applied in thicker films, improving appearance and productivity
Enhanced König hardness development With Solus 2100 Konig seconds 250 200 150 100 Hardness of 2K clearcoat based after baking (60 C/30min) Fast Drying Acrylic Fast drying acrylic Fast Fast Drying drying acrylic Acrylic +10% cellulose ester Cellulose Ester 50 0 0.01 0.1 1 10 100 1000 Time (hr) Solus can decrease drying time while achieving desired hardness, improving productivity
Enhanced pot life With Solus 2100 140 Viscosity double time (mins) 120 100 80 60 40 20 0 Fast Fast Drying drying Acrylic acrylic Fast Fast Drying drying Acrylic acrylic +10% +10% Cellulose cellulose ester Ester Increased pot life improves productivity and eliminates unnecessary waste of materials
Minimal VOC impact With Solus 2100 440 420 400 VOC (g/l) 380 360 340 320 300 Fast Fast Drying drying acrylic Acrylic Fast Fast Drying drying acrylic Acrylic +10% cellulose ester +10% Cellulose Ester With Solus, productivity and appearance can be improved while also meeting stringent VOC limits
Gloss 90 89 88 87 89 88.6 Gloss 20 (%) 86 85 84 83 82 81 80 Fast drying acrylic Fast Drying Acrylic Fast drying acrylic Fast Drying Acrylic +10% cellulose ester +10% Cellulose Ester With Solus, there is insignificant impact to gloss compared to control
Appearance measured by Wavescan Horizontal (Wavescan profile) Horizontal (Short and long wave) 12.0 4.5 10.0 8.0 Fast Fast Drying drying Acrylic acrylic Fast drying acrylic Fast Drying Acrylic + 10% +10% cellulose ester Cellulose Ester 4.0 3.5 3.0 6.0 2.5 2.0 4.0 1.5 2.0 1.0 0.5 0.0 du Wa Wb Wc Wd We 0.0 SW LW With Solus, there is measurable appearance improvement
Appearance Acrylic +10% cellulose ester
Cellulose esters reduce coating defects Picture framing Crater Pin hole Coating Substrate
Improved flow and leveling with CAB Pencil reflection in a coating Without CAB Poor flow / leveling Poor reflection With Eastman CAB-551-0.01 Good flow / leveling High reflection
CAB reduces flooding and floating in paint Solvent evaporation leads to localized surface cooling With CAB, rapid viscosity rise after application effectively locks pigments in position, delivering more even color and appearance
Similar mechanism for silica matting aids Light Reflected Light Scattered Silica particle Silica particle Without CAB Higher solids Lower film shrinkage Higher gloss With CAB Lower solids Higher film shrinkage Lower gloss With CAB, the performance of matting aids such as silica is increased due to higher film shrinkage
60 Gloss 2K acrylic urethane coating With silica matting aid at different film thicknesses 30 Acrylic control 25 Gloss 20 15 1: 0.3 Acrylic: CAB 10 1: 0.8 Acrylic: CAB 5 0 0 10 20 30 40 50 60 70 80 90 Thickness (Microns) With CAB, constant gloss levels are exhibited as dry film thickness increases.
Conclusion
Cellulose esters for automotive coatings Enhancing application and appearance Improves application Faster drying time Improved flow and leveling Increases solution viscosity faster Improved hardness development Smoother, more uniform paint film Improves appearance More consistent metallic flake orientation Improved color consistency Delivers compliance No negative impact to VOC Derived from renewable sources