ANIONIC EMULSIONS

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ANIONIC EMULSIONS

• FDU Lab
• Feb 4, 2008

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EMULSIFIERS

• Anionic
• Nonionic
• Cationic
• Steric

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ANIONIC
CATIONIC
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AMPHOTERIC
-

-

Higher-anionic
Lower-cationic
pH
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NONIONIC
Fatty Chain
Ethylene oxide
CH2 CH2 O
-CH2-CH2-O-
N
N
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STERIC
Example- Pemulen- Breaks with salt
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HOW STEARIC SOAPS WORK

• Ionic repulsion-electrical double layer
• Stearic tail in oil droplet
• Ionic heads in continuous water phase
• Ionic heads negatively charged, attract positive
  ions from water phase
• Double layer repels other dispersed droplets

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BASIC EMULSION
80 Water 20 Oil 10-15 Oil
phase as emulsifier
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IN SITU
For the common anionics, we add the fatty acid
and base to make the emulsifier.
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BEESWAX-BORAX

• Galen 200 AD- rose water in molten one part
  beeswax, 3-4 parts olive oil
• 1884- addition of borax to form sodium salt with
  free fatty acids
• Mineral oil to prevent rancidity by 1905
• Cerotic C25H31COOH key FA

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BASIC FORMULATION
13.5-14.5 of beeswax is free acid Guideline 5-7
wt beeswax wt borax
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TEA-STEARATE
Stearic acid CH3(CH2)16COOH Triethanolamine
(TEA) N(CH2CH2OH)3 TEA-Stearate is salt
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TYPICAL CREAM FORMULA

• 15 triple pressed stearic acid
• 1 KOH (80)
• 15 polyol
• 2 isopropyl myristate
• Qs water

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POLYOLS

• Propylene glycol- driest feel
• Sorbitol and ethoxylated sorbitol-medium feel
• Glycerin-wettest feel
• Use level 5-15

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STEARIC/PALMITIC
Ratio of stearic to palmitic effects viscosity
and appearance of creams

• Stearic/palmitic 75/25 to 50/50 gives best
  results
• Highest level stearic give most pearl but softest
  consistency

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STEARIC ACID SPECS
Emersol 132 NF
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ANALYTICAL DEFINITIONS
AV mg KOH to neutralize 1 gm fatty acid Eq. Wt.
Contains 1 atomic weight H2 (acid) Iodine
measure of unsaturation Saponification value mg
KOH to hydrolyze 1 gm ester (1 hour reflux)
SV AV Ester
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(No Transcript)
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NEUTRALIZATION
AV X Eq. Wt. Base gm base 56.1
1000 gm acid
AV stearic acid 210 Eq. Wt. TEA
149
210 X 149 0.556 56.1 1000
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pH TEA STEARATE
Exactly neutralized TEA-Stearate will have a very
high pH like any soap. An excess of stearic acid
will bring the pH down to a skin-friendly level.
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ALKALIES

• Sodium soaps make hard creams with poor sheen
• Potassium soaps make soft creams with good sheen
• Amides make soft creams with excellent sheen, but
  fear of nitrosamines
• Ammonia has bad odor

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SOME GOOD MIXES

• 1/9 NaOH/KOH
• 1/10 NaOH/KOH good texture, body, sheen
• TEA with NaOH, KOH or borax

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SOME ADVANTAGES

• Low cost
• Reliable
• Familiar

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DISADVANTAGES

• Irritation
• Crusting
• Poor freeze-thaw stability
• Some darkening over time (especially with TEA)

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STABILITY

• 25C one year
• 37C six months
• 45C three months
• 50C one month
• 4C one year
• -20C one month

Reaction rate doubles for every 10C rise in
temperature. Assume RT is 25C. BUT this is
an oversimplification!
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CYCLING

• -20 TO 25C
• -20 to 45C (dont return to room temperature)

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FORMULATING SKIN CARE EMULSIONS

• Target population
• Packaging
• Target cost of goods
• Product Claims
• Market leader
• Stability testing
• Choosing ingredients

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IMPROVING EMULSION STABILITY

• Preservation
• Package
• Thicken external phase
• Phase inversion
• Mixing temperature
• Mixing mechanics
• Cooling

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Next week HLB and Nonionic Emulsions