Overcoming the Obstacles in Formulating
Solvent-based Low VOC Acrylic Twocomponent Urethanes
Jeffrey Janos
Technical Specialist
JPCL Webinar
October 30, 2014
Overcoming the Obstacles in Formulating
Solvent-based Low VOC Acrylic Twocomponent Urethanes
 Low VOC - Definition
 Regulations/Drivers
 Acrylic Resin Manufacture
 Characteristics of Low Mw Acrylic Polyols
 Formulation Methods to Enhance Properties
 Test Methods
 Summary
What is a “VOC” in the coatings industry?
 Volatile organic compounds (VOCs) are organic
compounds (typically solvents) that have a high vapor
pressure at ordinary temperatures. Their high vapor pressure
results from a low boiling point, which causes large numbers
of molecules to evaporate into the surrounding air. These
“volatiles” can form the precursors of chemical smog. In the
United States and other locations globally, laws have been
created to limit the amounts of these materials released into
the atmosphere in an attempt to decrease air pollution.
Present VOC Regulations
National
AIM Rule1
Category
OTC 3,4/Canada
California
CARB
South Coast
*See Below
Current
Current
New SCM 2010
Current
Current
Sanding Sealers
550
350
275
275**
275
Primer, Sealer, Under
coaters
400
200
100
100
200
Quick Dry Sealers
450
200
275
100
200
Lacquer Sanding Sealer
680
550
275
275**
550
550
250
250
2502
2505
Varnishes (W/B, S/B, 2K )
450
350
275
275**
350
Conversion Varnish
725
350
275
275**
725
-
-
-
-
450
680
550
275
275**
550
-
680
275
275**
680
730
730
730
730***
730
SEALERS
STAINS
Stain, Semi-transparent
TOPCOATS/FINISHES
Conjugated Oil Varnish
Lacquers
Clear Brushing Lacquer
Shellacs – Clear
See “footnotes” at end of presentation
Manufacture of Acrylic Polyol Resins
 Processes
 Solution Batch & Semibatch Process
 Continuous Stirred-tank
Process
 Plug Flow Process
Polymer “Batch” Reactor
S o lv e n t,
M o n o m e r,
In itia to r
A n e v a p o ra to r
A b ig ta n k
Or
A v a lv e
U s e D ire c tly
Methods of Formulating Low VOC Acrylic
Urethanes
 Use of low viscosity acrylic
polyols
 Reactive diluents
 Use of low viscosity
isocyanates
 Exempt solvents
 Fillers
Low Viscosity Acrylic Polyols
 Acrylic Resins with Low
Viscosities
 Explanation
 Low molecular weight
→ Lower hydrodynamic volume
 Molecules with fewer polar
groups (-COOH, Urethanes, etc.)
→ Less intermolecular hydrogen
bonding
 Low polydispersity (Mw/Mn)
→ Less high Mw compounds
 Using branched molecules
→ Lower hydrodynamic volume
 Using solutions with good
solubility
→ Formulation of gel-like structures
prevented
 Low glass transition (Tg)
temperatures
→ Lower hydrodynamic volume
Low Mw Acrylic Polyols
 Positives
 Negatives
 Lower solvent release
 Slower cure
 Ability to apply with less coats
 Weatherability
 Chemical resistance
 Corrosion resistance
 Lower abrasion resistance
 Slower hardness development
 More difficult to control gloss
 Cost
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Slower Cure
 Increase catalyst levels
 Use more reactive diluents
 Use modified “fast cure”
polyols
 Use more reactive
isocyanates
 Use blends of other faster
reacting resins with the acrylic
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Weatherability
 Use combinations of hindered
amines & UV absorbers
7.0
 Minimize use of monomers
with poor UV resistance
5.0
 Use blends of higher Tg &
lower Tg acrylics
 Increase opacity
 Nano-TiO2
 Minimize the amount of
catalyst in the formulation
Color Change QUVA
8.0
473 Hrs
1000 Hrs
6.0
1639 Hrs
ΔE
4.0
3.0
2.0
1.0
0.0
Acrylic A
Acrylic A
w/ UVA
Acrylic B
Acrylic B Polyester Polyester
w/UVA
w/ UVA
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Chemical/Corrosion
Resistance
 Increase crosslink density
 Increase Tg of film
 Use blends of higher Tg &
lower Tg acrylics
 Hydrophobic additives
 Over indexing with isocyanates
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Lower Abrasion Resistance
 Incorporation of resin
“tougheners” like linear acrylics,
polyesters, amines &
caprolactones
 Surface active ingredients
 Slight under indexing with
isocyanates
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Slower Hardness
Development
 Increase catalyst amounts or
change to a more reactive one
 Use blends of higher Tg &
lower Tg acrylics
 Increase pigment to binder
ratio
König Hardness over Time
140
120
H
a
r
d
n
e
s
s
100
80
1 Day
3 Days
60
7 Days
40
30 Days
20
0
High Mw
Med. High
Mw
Med. Mw
Acrylic Urethanes
Low Mw
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Difficult to Control Gloss
 Amorphous, treated silica
aerogels
 High molecular weight waxes
 Polymeric resin matting agents
Formulation Tips to Enhance the
Performance of Low Mw Acrylic Polyols
 Cost
 Increased isocyanate demand
 Higher solids
 Use of specialty monomers
Formulation Tips to Enhance the
Performance when using Exempt
Solvents
 USA
→ Acetone, methyl acetate, PCBTF,
t-BAC, dimethyl carbonate &
propylene carbonate in some
locations
 Canada
→ Acetone, methyl acetate, PCBTF,
t-BAC
 Global
→ Check local regulations
Formulation Tips to Enhance the
Performance when using Reactive
Diluents
 Low Tg acrylics
→ Can improve flexibility,
weathering
 Low Mw polyesters or diols
→ Flexibility
 OH functional oils
→ Castor types, add color to system
 Oxazolidine
→ Moisture activated
 Other amine functional
resins
→ Ketimine, aspartic, aldimine
Formulation Tips to Enhance the
Performance when using Fillers
 Minerals
→ Low oil absorption talcs, barytes,
carbonates
 Glass or mineral spheres
→ Low density, minimal surface
area but expensive
 Polymeric
→ Special purpose but expensive
Formulation Tips to Enhance the
Performance when using Low Viscosity
Isocyanates
 Low viscosity HDI trimers
(Isocyanates)
 Best performance
 HDI allophanates
 Lower crosslink density
 HDI uretdiones
 Lower crosslink density
Test Methods
 Hardness & Hardness
Development
 Pencil – ASTM D3363
 Pendulum Hardness –
ASTM D4366, ISO1522
6B 5B 4B 3B 2B B HB F H 2H 3H 4H 5H 6H 7H 8H 9H
Softer
Harder
König Pendulum Hardness - Clears
140
120
Swings
100
80
60
40
Days
20
0
Acrylic Urethanes
1
3
7 30
Test Methods
 Weathering
 QUVA & B – ASTM G154
 Weather-O-Meter –
ASTM C1442
 Exterior Exposure (Florida,
Arizona, etc.) – ASTM 7869,
7356
Test Methods
 Corrosion Resistance
 Salt Spray – ASTM B117
 Cyclic Prohesion – ASTM G85
Test Methods
 Dry Time
 Mechanical Method –
ASTM D5895
 Manual “Finger” Method –
ASTM D1640
 Pot-life
 Double Initial Viscosity –
ASTM D1084
Test Methods
 Abrasion Resistance
 Tabor Method – ASTM D4060
 “Falling Sand” Method –
ASTM D968
Test Methods
 Gloss
 Specular Gloss – ASTM D523
 Film Appearance
 Distinctness-of-Image –
ASTM D5767
Summary
 VOC regulations are becoming more & more significant to coating
manufacturing companies.
 Five primary methods of developing low VOC acrylic urethanes include
use of low molecular weight polyols, reactive diluents, low viscosity
isocyanates, exempt solvents & fillers.
 Low molecular weight acrylic systems have the lowest solvent content &
are globally accepted. Exempt systems are only applicable is regional
areas.
 Many short-comings of using low molecular weight acrylics can be
overcome or minimized by careful formulating techniques.
While the descriptions, designs, data and information contained herein are presented in good faith and
believed to be accurate, they are provided for guidance only. Because many factors may affect processing
or application/use, BASF recommends that the reader make tests to determine the suitability of a product for
a particular purpose prior to use. NO WARRANTIES OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
INCLUDING, BUT NOT LIMITED TO, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE, ARE MADE REGARDING PRODUCTS DESCRIBED OR DESIGNS, DATA OR
INFORMATION SET FORTH, OR THAT THE PRODUCTS, DESCRIPTIONS, DESIGNS, DATA OR
INFORMATION MAY BE USED WITHOUT INFRINGING THE INTELLECTUAL PROPERTY RIGHTS OF
OTHERS. In no case shall the descriptions, information, data or designs provided be considered a part of
BASF's terms and conditions of sale. Further, the descriptions, designs, data, and information furnished by
BASF hereunder are given gratis and BASF assumes no obligation or liability for the descriptions, designs,
data or information given or results obtained all such being given and accepted at the reader's risk.
® registered trademarks of BASF Group.
© BASF Corporation, 2014
Footnotes
*
OTC States: Connecticut, Delaware, District of Columbia, Maine (except varnish & stain), Maryland,
Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Virginia (Only
Northern Virginia & Fredericksburg Emissions Control Areas which includes: Arlington, Fairfax, Loudoun,
Prince William, Stafford & Spotsylvania Counties; Cities of Alexandria, Fairfax, Falls Church, Manassas,
Manassas Park & Fredericksburg).
**
Quart exemption has been eliminated for Varnishes, Sanding Sealer and Lacquers in the South Coast
Air District
***
Shellacs manufactured after 12/31/06 are not allowed to be used on wood flooring in South Coast
1- EPA revising the National AIM Rule similar to OTC Phase I limits
2- Interior
3- RI adopted OTC Phase I
4- LADCO States – OH, IL & IN has adopted OTC Phase I limits, plus added Conjugated Oil Varnish
5- Interior Wiping Stains (Canada only)
Questions?