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

4

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

13

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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