74 JOURNAL OF COSMETIC SCIENCE
OPTIMIZING PERFORMANCE WHEN USING POLYMERS
IN SURFACTANT·8ASED CLEANSING PRODUCTS
Alan Suares, Patrick McCoy, Michael Myers, Steven Smith,
Julie Castner, Daniel Hasman and Julie Shlepr
Noveon., Inc., a wholly owned subsidiary of The Lubrizol Corporation
9911 Brecksville Road, Brecksville, OH 44141
Introduction
Acrylate polymers are widely used in surfactant cleansing systems for rheology modification,
suspension and stabilization. These polymers can enhance sensory properties, such as product appearance,
te.1ure. pourability and flow. ease of spreading and distribution and skin feel -propertiescriticaltosuccess
in the marketplace. Further. they offer advantages vs. salt thickening and other rheology modifiers in
improved flow (smooth vs. stringy or sticky) and appearance, suspension and stabilization.
Staying ahead in today's marketplace requires focus on creating the best formulations and on efficient
production, especially for high volume, high throughput products like shampoos, body washes and liquid
soaps. Critical decision points include total surfactant actives concentration and the type of surfactants to
be used desired pH: desired viscosity and flow characteristics the need for suspension of insoluble
particles whether the finished product is to be clear or opaque anticipated processing conditions and
storage and handling capabilities.
The objective of this work is to assist formulators and process engineers in the scale-up and
manufacturing of surfactant-based cleansing products which employ polymeric rheology modifiers.
Polymer properties. thickening mechanisms, formulating conditions and processing parameters most
critical to optimizing perfonnance and throughput are presented for:
TraditionaL highly crossJinked polyacrylic acid (PAA) polymers
Hydrophobically-modified. crosslinked acrylate copolymers such as Accylates/Cl0-30 Alkyl
Acrylate Crosspolymer
• Liquid rheology modifiers such as Acrylates Copolymer
Liquid, hydrophobically-modified. amine functional and crosslinked Polyacrylate-1 Crosspolymer
General Polymer Properties
General polymer properties in formulations are presented in Table I, showing physical form, flo�
profile. relative viscosity. relative yield value, clarity, relative ion tolerance and relative shear tolerance.
Thickening and stabilization mccban" in rfactaat sy ems
Traditional crosslinked PAA polymers build viscosity through charge-ihdua;d polyelectrolyte chain
expansion and hydrogen bonding. This creates a network of swollen, microgels
tightly packed in close contact ('"space-filling mechanism"). It is well known
through the literature• that dri\ing forces in polymer-surfactant interactions
include hydrophobic modification and electrostatic interaction. In cleansing
formulations. microge1 interactions are influenced by the presence of surfactant
micelles which also occupy space in the solution. Anionic surfactant micelles
repel anionic polymer microgels. thus reducing contact and viscosity. A high
relative viscosity and yield value profile can deliver adequate thickeningandstabilization. 1bese polymers
can form hydrogen bonds with formulation ingredients such as EO and/or PO nonionic surfactants, fatty
acids and polyols. Thickening occurs over time through the fonoation of large, cooperative structures, but
rarely affects � final formulation.
With Acrylates/C 10-:-30 Alkyl Acrylate Crosspolymer, thickening occurs upon neutralization due to
charge repulsion (hydrodynamic volume expansion). Again, ii is primarily the physical packing of polymer
microgels which provides viscosity and suspending capabilities. This polymer has moderately high ion
tolerance and thus. maintains good integrity in the presence of electrolytes.
Though not associative by chemistry. Acrylates Copo]ymer shows unique behavior.·Itinteracts with
surfactant systems in a way that is pH dependent. Thickening occurs via hydrodynamic volume expansion
and through interaction with surfactant micelles. The resulting three-dimensional networlc. enables
viscosity to be maintained in the presence of higher electrolyte content. The polymer builds viscosity at pH
6. but in the presence of typical anionic and amphoteric surfactaJ ts, a patented ""back-.acid thickening"
mechanism enables viscosity and suspension to be increased through the addition of an acid, like citric
acid. The polymer offers synergistic thickening with surfactants and salt.

2006 ANNUAL SCIENTIFIC MEETING 75
Polyacrylate-1 Crosspolymer presents a novel thickening mechanism for lower pH formulations or in
formulations containing cationic ingredients. This cationic-compatible polymer builds viscosity through
the mechanisms of hydrodynamic volume expansion. plus controlled hydrophobic association which occurs
when pH is reduced to 6. The thickening, suspension and stabilization properties of this polymer can be
further optimized in neutralized surfactant-based cleansing systems through the addition of a base, such as
sodium hydroxide. using a process known as "back-alkaline thickening''. Tilis polymer also offers
synergistic thickening with surfactants and salt when formulatod with suitable surfactant systems.
Formulating Conditions &Proces ing Paramden
Dispersion
One way of improving the manufacturing throughput of cleansing products is to reduce cycle time. This
is possible by reducing polymer dispersion time or making pre-dispersions. Traditional carbomer powders
typically require careful addition to the water portion of the formulation, have a longer hydration time and
require vigorous agitation. Acrylates/Cl0-30 Alkyl Acrylate Crosspolymer is a rapid self-wetting polymer
that requires no dispersion agitation. In a lab comparison at 25°C, the wetting time using 0.5 wt.% polymer
for traditional carbomer was 50 minutes. while Acrylates/CI0-30 Alkyl Acrylate Crosspolymer wet in just
3 minutes. Wetting time can be further reduced by increasing water temperature, with best results between
25 -50°C. Further. this polymer can be dispersed at concentrations up to 6.0 wt.% and still remain
pumpable. Liquid rheology modifiers, such as Acrylates Copolymer and Polyacrylate-1 Crosspolymer, are
even simpler. Specifics on dispersion method and dispersion times are presented in Table 2.
Order of Addition
Particularly with liquid rheology modifiers, such as Acrylates
Copolymer, order of addition is critical in getting both the best
performance and the greatest efficiency. Order of addition and
other efficiency tips are shown in Table 3.
Yield value is the initial resistance to flow under applied stress.
Yield value -not viscosity -is the dominant factor in detennining
suspending ability. This is critical in product formulation. Model
cleansing fonnulations will be shoMI. Yield value, and the advantages of using Acrylates Copolymer are
clearly demonstrated in the Pearlized 2-in-1 Conditioning Shampoo (SH-0024 A&B), where the three­
dimensional network enables the mica to maintain a stable. brilliant appearance over time.
Storage, Handling and Cleaning Procedures
When using liquid polymers, it is ex1remely important to use clean storage vessels and transfer
equipment, and to maintain temperature exposure within recommended limits. Care should be taken to
avoid forming foam during material transfer, to avoid conditions exposing the polymer to high shear and to
avoid use of piping susceptible to temperature extremes. With rheology modifier polymers, thorough
cleaning should be done after manufacturing, assuring tanks and transfer lines are well cleaned. The use of
good manufacturing practices will assure trouble-free performance, minimize batch-to-batch variation,
reduce unnecessary strain on equipment and avoid rework. Recommended storage and brief handling
procedures are presented in Table 4, and cleaning procedures are referenced in Table S.
An often overlooked issue that can impact polymer performance in cleansing applications is when
technology is transferred from an operation experienced in handling and formulating with newer polymer
technologies (such as Acrylates/Cl0-30 Alkyl Acrylate Crosspolymer, Acrylates Copolymer or
Polyacrylate-1 Crosspolymer) to one which is less experienced. To achieve optimal results, these novel
polymers require correct handling, designed specifically for their molecular architecture. Understanding
this can assure optimized performance when using polymers in surfactant-based cleansing product
fonnulations.
'E. D. Goddard and KP. Ananthapadmanabhan, Ed., lntemctions of Surfactants with Polymers and Proteins, Ch. 5,
(1993). 'us patents 6767878 and 6897253.
'Patent-pending.