Structured Acrylate Copolymer Thickeners
Publication Date: 2010-Oct-01
The IP.com Prior Art Database
Disclosed are multi-staged acrylic based core-shell polymers comprising a linear core polymer and at least one subsequently polymerized shell polymer. At least one of the subsequently polymerized shell polymers is crosslinked. The core-shell polymers surprisingly provide desirable rheological, clarity, and aesthetic properties in aqueous surfactant containing compositions, particularly at low pH.
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STRUCTURED ACRYLATE COPOLYMER THICKENERS
 In one aspect, the present invention relates to acrylic based staged core-shell polymers comprising a linear core and at least one crosslinked outer shell. In another aspect, the invention relates to an acrylic based staged core- shell polymer thickener suitable for use in aqueous systems. A further aspect of the invention relates to the formation of stable, aqueous compositions containing a acrylic based staged core-shell polymer rheology modifier, a surfactant, and optionally various components that are substantially insoluble materials requiring suspension or stabilization. Additionally, a further aspect of the invention relates to the formation of clear, rheologically and phase stable surfactant compositions formulated at low pH ranges.
BACKGROUND OF THE INVENTION
 Rheology modifiers, also referred to as thickeners or viscosifiers, are ubiquitous in surfactant containing personal care cleansing formulations. Rheological properties (e.g., viscosity and flow characteristics, foamability, spreadability, and the like), aesthetic properties (e.g., clarity, sensory effects, and the like), mildness (dermal and ocular irritation mitigation), and the ability to suspend and stabilize soluble and insoluble components within a surfactant based formulation are often modified by the addition of a thickener.
 Often, thickeners are introduced into surfactant formulations in solid form and mixed under conditions effective to dissolve the thickener into the liquid surfactant composition in order to effect a viscosity enhancement. Frequently, the mixing must be conducted at elevated temperatures (hot processing) in order to promote the dissolution of the solid thickener and obtain the desired viscosity improvement. Additionally, solid thickeners (e.g., carbomer powders) are known to resist "wet-out" upon contact with the surface of an aqueous based system. Consequently, carbomers are supplied as finely divided powders and/or must be sifted to reduce particle size which aids in dissolution by increasing the relative surface area of the particle. During processing carbomer powders can become electrostatically charged as they are transferred in and out of containers and
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tend to adhere to oppositely charged surfaces including airborne dust, necessitating specialized dust extraction equipment. This means that preparation of aqueous dispersions is messy and time-consuming unless special precautions and expensive equipment is employed. Formulators of compositions containing thickened surfactant constituents desire the ability to formulate their products at ambient temperatures (cold processing). Accordingly, formulators desire thickeners which can be introduced to the liquid surfactant compositions in liquid form rather than as a solid. This provides the formulator with a greater degree of precision in introducing the thickener to the liquid surfactant...