Waterborne Epoxy Products

1
VOC-free Waterborne Epoxy Emulsions and
Dispersions for Ambient Cure Coatings
2
Waterborne Epoxy dispersions?

• Stricter legislation is limiting the use of
  solvents-Volatile Organic Compounds (VOC) in
  paints e.g.
• European directive 1999/13/EC and amendment
  2004/42/EC
• first stage implemented in 2007
• second stage implemented in 2010
• U.S. 3 major organizations driving the reduction
  of VOC
• Environmental Protection Agency (EPA, through
  Clean Air Act)
• South Coast Air Quality Management District
  (SCAQMD)
• Ozone Transportation Commission (OTC)
• Green Image environmental friendly coatings
• Low odor, low flammability
• Easy cleaning of equipment with water
• Making use of the excellent properties of Epoxy
  resins (e.g. corrosion
• resistance, chemical resistance, adhesion,) with
  minimal amounts
• of solvent to fulfill legal and environmental
  requirements

3
Drivers and alternative approaches

• Typical solvent borne formulations for Marine and
  Protective coatings are based on epoxy resin
  grades with an Epoxy Equivalent Weight of 500
  gr/eq containing solvents like Xylene
• Typical solvent content of these solid epoxy
  resin solutions is 25
• Major contributor to the overall VOC content of a
  solvent borne formulation
• Several approaches exist to minimize or eliminate
  the VOC content
• High solids coatings
• Powder coatings
• Radiation cured coatings
• Waterborne coatings

4
Dows Technology Approach

• Dow technology
• Non ionic surfactant was especially developed for
  WB epoxy resins
• Surfactant is epoxy functional so that it will be
  part of the cured matrix
• Unique dispersion process which allows mono
  modular and submicron particle size distributions
• Submicron particle size distributions allow a
  good storage stability and film formation
• Formulator can use solvent of choice
• No additional solvent, so low VOC formulations
  can be prepared
• Grades
• Emulsion of a Liquid Epoxy Resin commercial
  grade
• Dispersion of an Epoxy Novolac Resin commercial
  grade
• Dispersion of a Solid Epoxy Resin commercial
  grade

Chemistry

Process
Properties
Ambient cured coatings
5
VOC free WB epoxy dispersions
Aqueous dispersion based on Liquid Epoxy Resin SolidEpoxyResin Epoxy Novolac Resin
Grade XZ 92598.00 XZ 92533.00 XZ 92546.00
Epoxy Equivalent Weight (gr/eq) 194 204 475 500 184 204
Solid content 60 - 75 46 - 48 56 - 59
Viscosity _at_ 23 CBrookfield, mPas 3000 - 30.000 3000 - 9000 5000 - 10.000
Typical average Particle size D4.3 0.5 µm 0.5 µm 0.5 µm
6
Typical Particle Size distributions
Particle size distribution of an aqueous
dispersion of an epoxy novolac resin
Particle size distribution of an aqueous
dispersion of a solid epoxy resin
7
Storage Stability
Submicron particle size distributions lead to
excellent storage stabilities demonstrated with
the example of a WB epoxy novolac dispersion XZ
92546.00
Weeks of storage Average particle size D4.3 Epoxy Equivalent Weight Brookfield viscosity at 23C
0 0.385 µm 190 g/eq 4660 mPas
27 0.385 µm 191 g/eq 4200 mPas
56 0.390 µm 191 g/eq 4200 mPas
Only very light sediment after one year of
storage at 23C which can be easily stirred in
8
Viscosity profile of epoxy dispersion
XZ 92533.00 Good shear thinning properties
allowing good flow and spray properties
Solid contents up to 54 without solvents can be
achieved if high viscosities can be tolerated
9
Mechanical dispersion Process

• Process patented by Dow
• Continuous feed of resin and water to the
  mixing unit under high shear
• High viscous resins can be dispersed without
  the addition of solvents
• Excellent transfer of process parameters from
  lab to pilot to manufacturing scale
• Submicron and mono modular particle size
  distributions

10
Influence of process parameters
Particle size can be influenced by the total flow
rate
11
Influence of process parameters
Significant increase in viscosity with
decreasing particle size distribution
12
Solid Epoxy Resin Dispersion
13
Cure Rate
Both Curing agents are based on water soluble
epoxy amine adducts
Drying times based on drying time recorder
Curing agent 1 Curing agent 2
End of gel tear 2.9 h 2.4 h
End of scratch 7 h 9.4 h
14
Pot life
As 2K WB epoxy systems dont have necessarily a
visible end of pot life like their solvent borne
counterparts other properties are tested
Some 2K WB epoxy systems based on Dows
dispersion technology show excellent gloss
retention over time
15
Anti-corrosive Primer White
Component A Weight- 1 Curing Agent
2 13,4 2 Demineralised water 29,1 3 TEGO
Dispers 750W Tego-Chemie 1,6 4 BYK 019 / 024
(32) BYK Chemie 0,5 5 Omya BLR 3
Omya 17,5 6 Micro-Talc AT Extra Omya 9,0 7
Micro-Talc AT 1 Omya 8,0 8 Heucophos
ZPA Heubach 10,0 9 Kronos 2059 Kronos 10,0 1
0 Aerosil R 972 Degussa 0.9 Total Component
A 100,0 Component B 1-Type Dispersion 87,0
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Barrier properties

• Good barrier properties against solvents,
  water and basic materials
• The clear coated systems show some minor
  deficiencies against some acids
• Fully formulated systems based on commercial
  available anticorrosion pigments achieve 1000
  hours of salt spray resistance on pretreated
  steel panels
• Corrosion/salt spray resistance on cold rolled
  steel of 1000 hours could be achieved with
  the help of adhesion promoters e.g. based on
  epoxy silane chemistry

17
Salt-Spray Test DIN 50021

• Exposure 1000 hours
• Blistering none (m0g0)
• Under rusting lt1 mm
• Adhesion lt GT1
• Scratch-Test o.k. (K0)
• Substrate
• Cold Rolled Steel, Type R-46 (Q-panel)

18
Institutional Coating
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Pot-life and Drying
Dry Times (1.5 mil dry films) Set-To-Touch 0.4
hrs. Surface Dry 0.6 hrs. Dry
Through 5.0 hrs.
20 Degree Gloss No Induction 101 30 Min. 101 1
Hr. 101 2 Hr. 92 3.5 Hrs. 78 4.5 Hrs. 65
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Resistance

• Cure 14 days _at_ R.T. conditions of 72 0F and
  50-55 R.H.
• Test Method ASTM D-1308 ( covered spot test, 18
  hr. exposure time, no recovery)

21
Combination Epoxy / PU Dispersion

• Combinations are possible but appropriate
  hardener selection is required (clarity)
• Gloss of cured mixtures is in the same high range
  as for the PUD alone
• Flexibility is improved when PUD is added to
  Epoxy Dispersions
• Coating hardness follows the ratio of Epoxy to
  PUD for 90 stoichiometric hardener ratio.
• Especially solvent resistance is improved when
  epoxy dispersion is added to the PUD

22
Conclusions
epoxy functional surfactant
Continuous process

VOC free WB epoxy dispersions
Excellent storage stability, film formation,
mechanical properties, barrier properties
Good fit for ambient cured coatings
also in combination with DOW PUDs