Post on 17-Jan-2016
High Performing Waterborne Acrylic Direct-to-Metal Coatings below 50 g/L
Laura Vielhauer
Leo Procopio, Mary Kate McCrea, and Bridget Dombroski
The Dow Chemical Company
Western Coatings Symposium 2015 – Las Vegas, NV
October 25-28, 2015
®Trademark of The Dow Chemical Company
Dow Coating Materials
Outline
• Market Perspective: Industrial Waterborne Acrylic Coatings
• Waterborne Acrylic Binder for DTM Coatings under 50 g/L VOC
• Challenges of lowering VOC levels
• Technical approaches and objectives
• Testing results and comparison to commercial DTM coatings
• Summary
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Market Perspective
Waterborne Acrylics in Industrial Coatings
Field-applied industrial maintenance coatings for metal and concrete
Traffic and roadmarking paints
Elastomeric roof coatings
General industrial finishing
Plastic coatings
Concrete and metal roof tiles
Fiber cement siding
Wood and wood composite coatings: e.g., cabinets, furniture, joinery
Coil coatings
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Industrial Maintenance Market: Technology Distribution
Source: US Paint & Coatings Market Analysis (2010 – 2015)
Alkyd12%
WB Acrylic24%
Polyurethane15%
Epoxy35%
Other14%
Distribution by volume, total volume 52.1 MM gallons (2010)
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Industrial Maintenance Applications Using WB Acrylics
Storage tanks Bridges Railcars Metal Buildings Commercial Architectural
Shipping Containers
Structural Steelwork Water Towers Pipes
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Benefits & Challenges of Waterborne Acrylic Coatings
Benefits
Low VOC = less impact on environment
Low odor
Less concern over worker exposure to
hazardous solvents
Better “cycle time” for various trades
Lower risk of fire from handling flammable
solvents
Easy and safer cleanup
Less waste and hazardous disposal
Ease of use
Proven performance in real world
applications
Challenges
• Application window, i.e., length of
painting season
• Drying rate dependent on humidity
• Reduced water resistance
• Often reduced substrate wetting
• Open time
• Film formation
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Waterborne Acrylic DTM Coatings under 50 g/L VOC
Challenges of Lowering VOC levels
• Trend in maintenance coatings is towards lower VOC, e.g., SCAQMD limit currently at 100 g/L
• Challenges presented when lowering VOC:
• Hardness• Block and print resistance• Dirt pickup resistance• Maintaining good film formation
• Market also wants higher performance
• Gloss and Durability• Corrosion resistance• Hiding
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Technical Approaches to Balancing VOC and Hardness in a Latex Coating
Some methods that have been used to lower VOC demand while trying to maintain hardness properties and good film formation:
• Lower Tg
• Lower coalescent level
• Use of non-volatile coalescent / plasticizer
• Blends of hard/soft
• Latex morphology, e.g., core-shell
Multi-Domain Core/Shell Blends
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Development Objectives for Low VOC Acrylic DTM Resin
Significant reduction in VOC: Capability of < 50 g/L
• Anticipating future industrial coating regulations• DTMs are increasingly used in the architectural space
Maintain (or improve) properties relative to higher VOC binders• Hardness properties• High performance of recent generation of DTM binders
(e.g., based on latex-pigment composites)• Corrosion resistance• Gloss / Gloss retention
Broad utility in both industrial and architectural applications
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New Latex Polymer for High Performance DTMs
*These properties are typical but do not constitute specifications.
Typical Physical Properties*
•Self-crosslinking
•APEO-free (made without the use of APEO surfactants)
Polymer AC-1
Solids 48.5 %
pH 8.5 – 9.5
Viscosity < 500 cP
MFFT 14 C
VOC capability < 50 g/L
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Technical Innovations
• Polymer composition and latex morphology to achieve good film formation with low coalescent demand and with minimal impact on hardness properties
• Self-crosslinking to improve dirt pickup resistance, chemical/solvent resistance and durability
• Optimization of pigment dispersion and corresponding properties via formation of latex polymer / pigment composite particles
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Latex-Pigment Composites
Formation of latex-pigment composites has been previously shown to help improve:• Corrosion resistance• Gloss potential• Durability (gloss retention)• Hiding
Composite particle formation
SEM image oflatex-pigment
composite
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Paint Surface Characterization
The DTM coating based on AC-1 shows more uniform distribution of TiO2.
AC-1 Conventional Latex
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Gloss DTM Screening Formulation Ingredients Weight (lbs)Water 60.00Dispersant 7.43Surfactant 4.00Defoamer 1.00Ammonia (28%) 2.00Titanium dioxide 210.00Grind for 30 minutes before adding:Water 20.00 Grind Sub-Total 304.43AC-1 Resin 527.79Water 100.00Ammonia (15%) 2.00Surfactant 0.46Dipropylene glycol n-butylether 15.36Sodium Nitrite (15%) 9.00Water 22.57HEUR rheology modifier (ICI driver) 24.00HEUR rheology modifier (KU driver) 3.00 Total 1008.61
Properties Total Volume 100.00 galPVC 17.5%Volume Solids 36.0%Coalescent level (on polymer) 6.0%VOC (calculated) ~50 g/L
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Description of commercial DTM benchmarks
DTM-1 was compared to three commercial WB acrylic DTM coatings:
Paint # COM-1 COM-2 COM-3
Description Commercial gloss white DTM
Commercial gloss white DTM
Commercial gloss white DTM
Volume Solids 35% 40% 38%
pH 9.2 9.5 8.9
VOC (g/L) <50 <100 <200
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Initial Paint Properties, Gloss, and Low T coalescence
Paint # DTM-1 DTM-2 COM-1 COM-2 COM-3
Description AC-1 AC-1 Commercial
Commercial
Commercial
% coalescent 6% 7%
VOC (g/L) <50 <50 < 50 <100 <200
Viscosity (KU) 95 98 116 79 87
Viscosity (ICI) 0.90 0.95 0.80 0.80 0.60
pH 9.2 9.3 9.2 9.5 8.9
Gloss (20/60) 58 / 81 59 / 82 65 / 84 57 / 83 35 / 73
LTFF (pass/fail @ 40F/40% RH)
slight cracking
pass fail pass fail
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Hardness Devopement
Metal Adhesion, Flexibility
Paint # DTM-1 COM-1 COM-2 COM-3
Description AC-1 Commercial Commercial Commercial
% coalescent 6%
VOC (g/L) <50 < 50 <100 <200
Adhesion (7 day)
CRS 4B 2B 5B 4B
Aluminum 4B 0B 0B 5B
Impact (direct/indirect) >140 in lb >140 in lb >140 in lb >140 in lb
Mandrel Bend pass 1/8” pass 1/8” pass 1/8” pass 1/8”
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Tack Results
Paint # DTM-1 DTM-2 COM-1 COM-2 COM-3
Description AC-1 AC-1 Commercial Commercial
Commercial
% coalescent 6% 7%
VOC (g/L) <50 <50 < 50 <100 <200
Zapon Tack test (g)
1 day 200 20 500 500 250
7 day 500 500 500 500 500
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Block Resistance Results
1 day Block Resistance
7 day Block Resistance0
1
2
3
4
5
6
7
8
9
10
DTM-1 COM-1 COM-2 COM-3
Bloc
k Re
sist
ance
Rati
ng
1 day, 30 min. oven block 1 day, RT block
0
1
2
3
4
5
6
7
8
9
10
DTM-1 COM-1 COM-2 COM-3
Bloc
k Re
sist
ance
Rati
ng
7 days, 30 min. oven block 7 days, RT block
Dirt Pickup Resistance
Paint # DTM-1 COM-1 COM-2 COM-3
Description AC-1 Commercial Commercial Commercial
% coalescent 6%
VOC (g/L) <50 < 50 <100 <200
DPUR (w/ UV exposure)
Initial Y-ref 94.23 87.28 89.02 84.91
Final Y-ref 94.03 79.58 76.15 82.72
Delta Y-ref 0.20 7.70 12.87 2.19
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Gloss Retention, Humidity Resistance
Paint # DTM-1 COM-1 COM-2 COM-3
Description AC-1 Commercial Commercial Commercial
% coalescent 6%
VOC (g/L) <50 < 50 <100 <200
% 60 gloss retention (QUV A exposure)
1130 hrs 104% 48% 65% 17%
Cleveland cabinet (21 days)
blistering none 8F none 6F
rusting none 3G none 1G
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Blister rating (ASTM D714): D=Dense MD=Medium Dense M=Medium F=FewRust Rating (ASTM D610): S=Spots G=General P=Pinpoint
Corrosion Resistance
DTM-16% coalescent
DTM-27% coalescent
COM-3<200 VOC576 hours
COM-1<50 VOC576 hours
COM-2<100 VOC
DTM-38% coalescent
1000 hrs Salt Spray Exposure over CRS
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Corrosion Resistance
DTM-16% coalescent
DTM-27% coalescent
COM-3<200 VOC576 hours
COM-1<50 VOC
576 hours
COM-2<100 VOC
DTM-38% coalescent
1000 hrs Salt Spray Exposure over blasted BHRS
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Summary of Performance
The new low VOC DTM binder has an excellent balance of properties at < 50 g/L
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Conclusions
• A new acrylic resin has been developed for WB DTM coatings and offers an excellent balance of properties, including:
Low VOC, less than 50 g/L VOC Properties related to film hardness – hardness, block, tack, DPUR Good film formation - LTFF, Corrosion resistance Durability
• Recommended applications include industrial maintenance, light duty commercial/architectural and DIY coatings for metal and concrete
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