Features

Silicone Emulsifier Selection for Organic Oils and Butters

August 3, 2009

Silicone emulsifiers and organic materials can be formulated together to produce a balance of sensory characteristics, functions and claims.

Silicone Emulsifier Selection for Organic Oils and Butters



Silicone emulsifiers and organic materials can be formulated together to produce a balance of sensory characteristics, functions and claims.



Bill Marthaler
Technology and Development Manager
Shin-Etsu Silicones



Cosmetic chemists are using more organic oils and butters in their formulas. However, numerous studies indicate that silicones cannot be replaced by organics in cosmetic formulations without a loss of desired sensory characteristics and functionality. The challenge to the cosmetic chemist is to combine silicone and organic materials to achieve a balance of sensory characteristics, functions and claims. With the use of silicone emulsifiers, the cosmetic chemist can combine silicone materials with organics to achieve this goal.

Examples of organic and silicone emulsions produced with silicone emulsifiers are described in detail.

Types of Emulsions



Emulsions are typically water-in-oil or oil-in-water. For this article, the oil portion can be silicone, organic or a combination of both.

A simple emulsion consists of an oil phase, an emulsifier package and a water phase. To construct this simple emulsion, the internal phase is added to the outer phase with high agitation mixing such as disper blending or homogenization. Silicone-containing emulsions are normally constructed at room temperature. Only those with ingredients that are solid at room temperature are constructed with enough heat to melt the solids.

To create different products, additional materials such as emollients, thickeners, secondary emulsifiers, film formers, powders and sunblocks are added to the formula.

Some of these materials include: dimethicones, which act as diluents and emollients; dimethicone gums (thickeners and conditioners); PEG-dimethicones (emulsifiers); polygly-cerol dimethicones (emulsifiers and humectant); amine modified silicones (conditioner); trimethylsiloxysilicates (film formers); dimethicone cross-polymer (thickeners and emollients); acrylates/dimethicones (film formers); silsesquioxane cross-polymer powders (soft focus and skin feel) and treated TiO2 and ZnO (sunscreens in silicone).

These ingredients are added in the compatible phase or as an additional phase at the end of the mixing cycle.

Organic Materials



The compositions of some typical organics are shown in the chart at left. “Typical” is denoted because the composition can change with growing conditions. For example, coconut oil formulas exhibit shifts in viscosity months after “El Nino” occurs in the Pacific Ocean. This viscosity change is due to chain length shifts within the coconut oils driven by the altered weather conditions.

The key to producing stable emulsions is in emulsifier selection. Since silicone does not dissolve in water or organics, pendants are added to the silicone polymer to bring the different materials together. The principle of “like dissolves like” is used.

Fig 1: Types of Silicone Emulsifiers
To emulsify silicone in water or water in silicone, the workhorse linear polyether is the starting point. To gain enhanced stability and a lighter feel, a branched silicone emulsifier is selected. The polyglycerin system is used to gain humectancy. Polyglycerin can also give large particle sized emulsions. To incorporate an organic into an emulsion, alkyls are selected. The newer elastomer systems also give the advantage of stearic hindrance and can be used to build very large (95%) internal phase systems. These emulsions can range from 1 to 50 microns in size and incompatible materials can sometimes be kept apart in the different phases.

Using Silicone Emulsifiers



The following formulas demonstrate how silicone emulsifiers and organic materials can be used to produce elegant cosmetic products. The cosmetic chemist can easily add his expertise by adding favorite ingredients to the appropriate phases.

In the polyethyleneoxide-free silicone emulsifiers formula below, a polyglycerin crosspolymer is selected to give humectancy and a large internal phase. A co-emulsifier with lauryl and polyglyceral pendants helps hold the organic.

Polyethyleneoxide-Free Silicone Emulsifier


Ingredient%Wt.
Oil Phase
Dimethicone and 5
Polyglycerin-3 crosspolymer
Lauryl polyglyceryl-3 1
Polydimethyl siloxyethyl dimethicone
Mango butter24
Glycol Phase
DPG5
Water Phase
1% NaCl solution65

Procedure:
Combine the oil phase ingredients at 70°C. Combine the water phase ingredients at 70°C. Add the DPG slowly with disper mixing. Add the water phase to the oil phase slowly with disper mixing. Resulting viscosity: semi-solid. Aesthetics: Rich organic and a non-greasy after feel. Note: Viscosity will build for 24 hours as the butter re-crystallizes.

In the formula below, a polyethylene crosspolymer is selected to give a soft after feel and a large internal phase. A co-emulsifier with lauryl and polyethylene compliments the main emulsifier type.

Polyethylene-Containing Silicone Emulsifier


Ingredient%Wt.
Oil Phase
Dimethicone PEG 10/15 5
crosspolymer
Lauryl PEG-9 polydimethyl-1
siloxyethyl dimethicone
Mango butter 24
Glycol Phase
DPG5
Water Phase
1% NaCl solution65

Procedure:
Combine the oil phase ingredients at 70°C. Combine the water phase ingredients at 70°C. Add the DPG slowly to the oil phase with disper mixing. Add the water phases slowly with disper mixing. Form: semi-solid. Aesthetics: Rich organic and a non-greasy after feel. Note: Viscosity will build for 24 hours as the butter re-crystallizes.

Fig 2: Representation of an emulsifying cross-polymer

High Organic System with Dimethicone
& Petrolatum


Ingredient%Wt.
Oil Phase
Dimethicone and Polyglycerin-35.0
crosspolymer and dimethicone
Lauryl PEG-9 polydimethyl-1.0
siloxyethyl dimethicone
Shea butter57.0
Dimethicone 6 cs6.0
Petrolatum15.0
Glycol Phase
1-3 Butylene glycol5.0
Water Phase
Na citrate.2
NaCl.5
Water10.3

Procedure:
Combine the oil phase ingredients at 70°C. Combine the water phase ingredients at 70°C. Add the 1-3 butylene glycol to the oil phase with disper mixing. Add the water phases slowly. Form: semi-solid. Aesthetics: rich organic butter rub in with very smooth silicone after feel.

In the following two formulas, a robust emulsifying system is employed with exotic organic oils to impart cream and lotion textures.


Exotic Oil I


Ingredient%Wt.
Oil Phase
Dimethicone and polyglycerin-35.0
crosspolymer and dimethicone
PEG-9 polydimethylsiloxyethyl2.0
dimethicone
PEG-10 dimethicone2.0
Rice oil10.0
Methyl trimethicone5.0
1-3 butylene glycol5.0
Water Phase
Na citrate.2
Water70.8

Procedure:
Combine the oil phase ingredients at room temperature. Combine the water phase ingredients at room temperature. Add the 1-3 butylene glycol to the oil phase with disper mixing. Add the water phases slowly. Form: cream. Aesthetics: rich organic rub in with a very smooth silicone afterfeel.


Exotic Oil II


Ingredient%Wt.
Oil Phase
Dimethicone and polyglycerin-35.0
crosspolymer and dimethicone
PEG-9 polydimethylsiloxyethyl2.0
dimethicone
PEG-10 dimethicone2.0
Camellia oil10.0
Methyl trimethicone5.0
1-3 butylene glycol5.0
Water Phase
Na citrate.2
Water70.8

Procedure:
Combine the oil phase ingredients at room temperature. Combine the water phase ingredients at room temperature. Add the 1-3 butylene glycol to the oil phase with disper mixing. Add the water phases slowly. Form: lotion. Aesthetics: rich organic rub in with very smooth silicone after feel.


Some Formulation Tips


Here are some formulation tips to remember when working with silicone emulsions. Cyclopentasiloxane and dimethicone fluid 6cs can usually be interchanged. Preservatives should be added to the emulsifier system first for best stability results.

When starting an emulsion, the addition of a glycol before the water phase helps start the emulsion and can successfully build hard to combine emulsions. Salt helps stabilize silicone emulsions.
To improve freeze and thaw properties, increasing the amount of salt or glycol materials can make the water phase more “antifreeze-like.” Clear formulas are made by matching the refractive index of the oil and water phases.

Finally, cross-polymer type emulsions are extremely robust. Incom-patible materials can be held apart by the stearic hindrance properties of these emulsifiers. These crosspolymers are very large when compared to typical emulsifiers.

In conclusion, as this article demonstrates, organic-containing cosmetic silicone emulsions can be easily produced with silicone emulsifiers. By the examination of emulsifier form and pendants, the cosmetic chemist can set emulsion and aesthetic attributes of the final product.

For more information


To learn more about silicone emulsifiers and their applications in personal care products, contact Kari Walker, Shin-Etsu Silicones of America, Inc., Tel: 330.630.9860; Email: cosmetics@shinetsusilicones.com; Website: www.shinetsusilicones.com


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