Transcript Red Spot / BASF Tech Meeting
Overcoming the Obstacles in Formulating Solvent-based Low VOC Acrylic Two component Urethanes
Jeffrey Janos Technical Specialist JPCL Webinar October 30, 2014
Overcoming the Obstacles in Formulating Solvent-based Low VOC Acrylic Two component 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 Category National AIM Rule 1 Current SEALERS Sanding Sealers Primer, Sealer, Under coaters Quick Dry Sealers Lacquer Sanding Sealer 550 400 450 680 STAINS Stain, Semi-transparent TOPCOATS/FINISHES Varnishes (W/B, S/B, 2K ) Conversion Varnish 550 450 725 Conjugated Oil Varnish Lacquers Clear Brushing Lacquer 680 Shellacs – Clear 730
See “footnotes” at end of presentation
Current California CARB New SCM 2010 South Coast Current OTC 3,4 /Canada *See Below Current 350 200 200 550 250 350 350 550 680 730 275 100 275 275 250 275 275 275 275 730 275** 100 100 275** 250 2 275** 275** 275** 275** 730*** 275 200 200 550 250 5 350 725 450 550 680 730
Manufacture of Acrylic Polyol Resins
Processes
Solution Batch & Semi batch Process Continuous Stirred-tank Process Plug Flow Process
Polymer “Batch” Reactor
Solvent, Monomer, Initiator A valve A big tank Or Use Directly An evaporator
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
Low molecular weight Molecules with fewer polar groups (-COOH, Urethanes, etc.) Low polydispersity (Mw/Mn) Using branched molecules Using solutions with good solubility Low glass transition (Tg) temperatures
Explanation
→ Lower hydrodynamic volume → Less intermolecular hydrogen bonding → Less high Mw compounds → Lower hydrodynamic volume → Formulation of gel-like structures prevented → Lower hydrodynamic volume
Low Mw Acrylic Polyols
Positives
Lower solvent release Ability to apply with less coats
Negatives
Slower cure 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 Color Change QUVA
8,0 Use combinations of hindered amines & UV absorbers Minimize use of monomers with poor UV resistance Use blends of higher Tg & lower Tg acrylics Increase opacity Nano-TiO 2 Minimize the amount of catalyst in the formulation 7,0 6,0
ΔE
5,0 4,0 3,0 2,0 1,0 473 Hrs 1000 Hrs 1639 Hrs 0,0 Acrylic A Acrylic A w/ UVA Acrylic B Acrylic B w/UVA Polyester Polyester 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
140 120 Increase catalyst amounts or change to a more reactive one Use blends of higher Tg & lower Tg acrylics Increase pigment to binder ratio
H a r d n e s s
100 80 60 40 20 0
König Hardness over Time
High Mw Med. High Mw Med. Mw
Acrylic Urethanes
Low Mw 1 Day 3 Days 7 Days 30 Days
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
Canada
→ Acetone, methyl acetate, PCBTF, t-BAC, dimethyl carbonate & propylene carbonate in some locations → 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
Other amine functional resins
→ Moisture activated → 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
140 120 100 80 60 40 20 0
Acrylic Urethanes
1 3 7 30
Days
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)