presented to American Oil Chemist's Society May 2014. We investigate whether the HLD concepts can be applied to the formulation of ready to use hard surface cleaners. What are the complications?

1. Application of the HLD Microemulsion Model
for the Development of Phase Stable SOW
Type Hard Surface Cleaner Formulation
105th AOCS Annual Meeting and Expo
Division of Surfactants and Detergents, Session 4.1b
May 4-7, 2014, San Antonio, TX
E. Szekeres, M.M. Knock, R. Zhang, R. Khan, and D.R. Scheuing

2. Outline
• Background on ready to use (RTU) cleaner
formulations
• Goal and Strategy
• HLD model use for formulation support
• Experimental testing of model predictions
• Conclusions

3. RTU Cleaners and HLD model
• Ready to use (RTU) cleaners: hard surface spray
cleaners, wipe lotions, etc.
• Typical Composition:
Surfactants below 5% (lower is preferred)
Electrolytes (buffering/pH adjustment agents, etc.)
Fragrance below ~ 0.3%
Lots of water  water to oil ratio is extreme!
• Extreme high water to oil ratio may influence
applicability of HLD model
• These systems are single phase, unsaturated
microemulsions; may influence applicability of HLD
model

4. We like our RTU cleaners sparkling clear
Phase separation causes clouding, inhomogeneity
Phase separation is typically driven by fragrance
• Fragrance oils have low water solubility
• Surfactant micelles must solubilize fragrance well
Fragrance type impacts surfactant choice
• Surfactant and fragrance oil hydrophobicity must be
appropriately matched
• Must have enough surfactant to completely solubilize the
fragrance
• Surfactant system design can be very time consuming 
rely on HLD model to speed up work

5. Goal and Strategy
Goal
• Determine how well HLD model works for RTU surfactant
design
Strategy
• Use the HLD model to select surfactants for a two-surfactant
system that solubilizes a model fragrance oil
• Test the surfactant selection in the lab under realistic RTU
conditions
• Compare HLD predictions with lab findings
• Observe limitations

6. Model system
Composition
• 2% model oil ( EACN = 5.3) – represents the fragrance
• 0.5% NaCl – represent electrolytes
• No alcohol/cosolvent
• Two surfactants - Use the HLD model for surfactant selection
Design Criteria
• Single phase system
• Robust to temperature change
• Minimized surfactant concentration

7. HLD model
predicts microstructure of the self- assembly
HLD
Model
Electrolyte
Oil
Surfactant
Temperature
Cosolvent
HLD value
Input Output
HLD > 0
w/o
HLD < 0
o/w
HLD = 0
bicontinuous
Look for negative HLD, but close to zero

8. Two-surfactant formulation
Use HLD model
• Select one hydrophobic surfactant with HLD > 0
• Select one hydrophilic surfactant with HLD < 0
• Determine optimized surfactant mixing ratio to get to o/w
microemulsion region
• Ignore potential non-linearity of surfactant mixing
Go to the lab
• Do surfactant mixing ratio scan with WOR ~ 1 system to test
surfactant hydrophobicities and optimized surfactant mixing
ratio predicted by HLD model
• Do ratio scan under RTU conditions to see if predictions still
hold

9. The HLD model equations
For anionic surfactants: choose this as the hydrophobic surfactant
For nonionic surfactants: choose this as the hydrophilic surfactant
𝐻LD = 𝑙𝑛 𝑆 − 𝐸𝐴𝐶𝑁 ∙ 𝑘 + 𝐶𝑐 − 𝑎 𝑇 ∙ 𝑇 − 25 + 𝑓 𝐴
HLD = 𝑏 ∙ 𝑆 − 𝐸𝐴𝐶𝑁 ∙ 𝑘 + 𝐶𝑐 + 𝑎 𝑇 ∙ 𝑇 − 25 + 𝑓 𝐴
Electrolyte
Type/conc.
Oil type Surfactant
parameters
Temperature
coefficient
Cosolvent
function
Electrolyte coefficient
depends on surfactant
Sign of temperature
term opposite of anionic

10. Select anionic and nonionic surfactant for a model
oil (EACN = 5.3)
Salinity, NaCl wt% 0.5
T, Celsius 20
Oil EACN 5.3
k 0.16
αT, 1/Celsius 0.01
Optimum Cc at 20C 1.49
Anionic surfactants*
(Sulfonates, sulfosuccinates)
Non-ionic surfactants**
(Ethoxylates)
Salinity, NaCl wt% 0.5
T, Celsius 20
Oil EACN 5.3
k 0.16
αT, 1/Celsius 0.1
b 0.13
Optimum Cc at 20C 1.28
at 2C : Cc optimum = 1.31
at 49C: Cc optimum = 1.78
at 2C: Cc optimum = 3.08
at 49C: Cc optimum = -1.62
Choose AOT as the hydrophobic
surfactant (Cc = 2.55*) because
its Cc > 1.78
Choose Surfonic L12-8 as the
hydrophilic surfactant (Cc = - 5.7**)
because its Cc < - 1.62
* Formulating with the HLD-NAC; by Edgar J. Acosta, April 25-27, 2012. Pleasanton, California, USA
**based on Colloids and Surfaces A: Physicochem. Eng. Aspects 320 (2008) 193–204

11. Phase Inversion Predictions
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50
AOTweightratio
Temperature, C
Phase inversion (HLD = 0) predictions of
the model at 5% surfactant
w/o
o/w
• Formulation must remain o/w type across temperature range
• Blue line shows phase inversion between 0.7 – 0.9 AOT
weight fraction
• Model predicts only slight mixing ratio drift with temperature

12. WOR ~ 1 systems: Test tubes in line with HLD
predictions
“Fish”-like conditions (WOR=1.94, 3%
surfactant) at 20C
 Surfonic L12-8 is hydrophilic
as predicted
 AOT is hydrophobic as
predicted
 Liquid crystals form near
phase inversion
Model predicts phase inversion at AOT/Surfonic = 0.8
Test tubes suggest phase inversion between AOT/Surfonic = 0.73 and 0.82
Ignoring synergy is not detrimental
AOT
rich side
Surfonic
rich side
w/o o/w
Inversion
LC zone
3 phase system

13. RTU conditions: Test tubes in line with predictions
RTU cleaner-like conditions
(WOR=40, 3% surfactant, 2% oil) at
20C
 Surfactants keep their
hydrophobicity/hydrophilicity
 Liquid crystal impacted
region expands
 “formulation” to be shifted in
the hydrophilic direction to
avoid LC region
Liquid crystals obscure phase inversion
Phase inversion remains around AOT/Surfonic = 0.73 and 0.82
Liquid crystals must be tracked for formula optimization
AOT side
w/o
o/w
o/w
Inversion/LC zone
Inversion/LC zoneSingle phase tube
Excess oil
AOT
rich side
Surfonic
rich side

14. RTU systems: optimizing robustness requires
lab work
1.5 2 3 4 5 6 7
1 inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC
0.91 inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC
0.82 inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC
0.73 inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC inv/LC
0.64 X O inv/LC inv/LC inv/LC inv/LC inv/LC
0.55 X X O O inv/LC inv/LC inv/LC
0.45 X X X O O O O
0.36 X X X X O O O
0.27 X X X X X O O
0.18 X X X X X X O
0.09 X X X X X X X
0 X X X X X X X
Total surfactant concentration, wt%
AOTweightratio
HLD model outages:
• Ignores liquid crystals – surfactant mixing ratio deviation between
model and experiment increases at higher surfactant concentrations
• Doesn’t predict total surfactant concentrations (NAC model needed)
Phase behavior map of AOT, Surfonic L12-8, 2% model oil, 0.5% NaCl at T=20C

15. Testing the effect of temperature in lab
T=2C T=20C T=49C
1 inv/LC inv/LC inv/LC
0.91 inv/LC inv/LC inv/LC
0.82 inv/LC inv/LC inv/LC
0.73 inv/LC inv/LC inv/LC
0.64 inv/LC inv/LC inv/LC
0.55 O O O
0.45 X X O
0.36 X X O
0.27 X X X
0.18 X X X
0.09 X X X
0 X X X
• Model prediction of phase boundaries reflect realistic temperature effect
trends
• Liquid crystals cause deviation between model and experimental data
3% surfactant
AOTweightratio

16. Conclusions
• HLD model predictions quite worked well for WOR~1
systems
• For RTU type systems the HLD model gave
Appropriate surfactant selection guidance,
Approximate surfactant mixing ratio range for optimization
Realistic temperature effect trends
• Liquid crystalline phases cause deviation; lab work
necessary to stay away from LC regions
• Model gives good starting point for surfactant selection,
and can help save time for product development

17. We could choose the surfactant(s) appropriately
For the oil to be solubilized
We could check the effect of temperature, salt, etc.
To engineer sufficiently robust formulation
We would be able to select appropriate surfactants quickly
But we would have to still keep our lab coats!
So, if we knew the parameters……

18. Acknowledgments
Clorox
S&D Division, AOCS
Edgar Acosta for helpful discussions –
And You, The Audience and Consumer !

19. Appendix –
Calculation of the optimum Cc parameters
0 = 𝑙𝑛 𝑆 − 𝐸𝐴𝐶𝑁 ∙ 𝑘1 + 𝐶𝑐1 − 𝑎 𝑇1 ∙ 𝑇 − 25
Calculation of the optimum Cc parameters
0 = 𝑏 ∙ 𝑆 − 𝐸𝐴𝐶𝑁 ∙ 𝑘2 + 𝐶𝑐2 + 𝑎 𝑇2 ∙ 𝑇 − 25
For the anionic surfactant in the absence of alcohols the HLD equation becomes
At optimum 𝐻𝐿𝐷 = 0
𝐶𝑐1 = 𝐸𝐴𝐶𝑁 ∙ 𝑘1 − ln 𝑆 + 𝑎 𝑇1 ∙ 𝑇 − 25
Rearranging
For the non-ionic surfactant the HLD equation becomes
𝐶𝑐2 = 𝐸𝐴𝐶𝑁 ∙ 𝑘2 − 𝑏 ∙ 𝑆 − 𝑎 𝑇2 ∙ 𝑇 − 25
Rearranging

20. Appendix
Predicting the optimum surfactant mixing ratio
𝐻𝐿𝐷1 = 𝑙𝑛 𝑆 − 𝐸𝐴𝐶𝑁 ∙ 𝑘1 + 𝐶𝑐1 − 𝑎 𝑇1 ∙ 𝑇 − 25
Using linear mixing rule
𝐻𝐿𝐷2 = 𝑏 ∙ 𝑆 − 𝐸𝐴𝐶𝑁 ∙ 𝑘2 + 𝐶𝑐2 + 𝑎 𝑇2 ∙ 𝑇 − 25
𝐻𝐿𝐷 𝑚𝑖𝑥 = 𝑥 ∙ 𝐻𝐿𝐷1 + 1 − 𝑥 ∙ 𝐻𝐿𝐷2
where x = mole fraction of surfactant 1 (the anionic surfactant) in
the anionic/non-ionic surfactant mixture
Term f(A) drops out of the HLD equations in the absence of alcohol
Subscript 1 refers to the anionic surfactant
Subscript 2 refers to the non-ionic surfactant
At the phase inversion (optimum) point 𝐻𝐿𝐷 𝑚𝑖𝑥 = 0
The surfactant mixing ratio that brings about the phase inversion (optimum)
𝑥∗ =
𝐻𝐿𝐷2
𝐻𝐿𝐷2 − 𝐻𝐿𝐷1