Crosslinked PVP Thickener for Acidic Topical Compositions
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Solution Overview
Problem
Existing topical personal care and pharmaceutical compositions at low pH are challenging to thicken and maintain stability, often causing skin irritation due to the use of conventional thickeners that can lead to pilling or stringy textures, and high surfactant requirements.
Innovation Solution
The use of lightly- to moderately-crosslinked poly(N-vinyl-2-pyrrolidone) (PVP) as a thickener, which effectively stabilizes viscosity and pH even at extremely low pH levels, reducing skin irritation and providing smooth, thickened consistencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional thickeners (xanthan gum, magnesium aluminum silicate, acrylic acid polymers) are used in low pH compositions, then thickening is achieved, but skin irritation, pilling, and stringy texture occur
Solution Approach 1:
The patent changes the chemical parameters of the thickening agent by using lightly- to moderately-crosslinked PVP instead of conventional thickeners. This polymer maintains effective thickening at pH levels as low as 1.3, whereas conventional thickeners either fail to thicken or cause irritation at such low pH levels. The crosslinking degree and molecular weight of PVP are specifically optimized to achieve thickening without skin irritation.
Solution Approach 2:
The patent replaces expensive and problematic conventional thickeners with a more cost-effective and skin-friendly alternative. Lightly- to moderately-crosslinked PVP provides the necessary thickening at lower cost while eliminating the skin irritation and textural issues associated with xanthan gum, magnesium aluminum silicate, and acrylic acid polymers.
2Strength
If conventional thickeners are used at high addition levels to achieve thick consistency, then viscosity increases, but pilling and stringy texture are caused
Solution Approach 1:
The patent optimizes the concentration parameter of PVP to achieve effective thickening at lower addition levels (1-6% by weight) compared to conventional thickeners that require higher levels. This optimized concentration range provides the desired viscosity while maintaining formulary stability and preventing pilling and stringy texture formation.
Solution Approach 2:
The patent uses lightly- to moderately-crosslinked PVP as a composite polymer structure that combines the thickening capability of crosslinked polymers with the skin-friendly properties of PVP. This composite structure provides efficient thickening at low concentrations while maintaining composition stability and avoiding the defects of conventional thickeners.
3Strength
If acrylic acid polymers are used and neutralized to attain desired viscosity, then thickening is achieved, but the product cannot remain strongly acidic
Solution Approach 1:
The patent changes the pH parameter by using PVP that is effective at strongly acidic pH levels (as low as 1.3) without requiring neutralization. Conventional acrylic acid polymers must be neutralized to achieve thickening, which raises the pH and compromises the acidic efficacy of the composition. PVP maintains both thickening and acidic properties simultaneously.
4Reliability
If low pH compositions are used to provide skin benefits, then exfoliation and moisturization are enhanced, but skin irritation and discomfort increase
Solution Approach 1:
The patent introduces lightly- to moderately-crosslinked PVP as an intermediary substance that mediates between the low pH active ingredients and the skin. This polymer forms a protective matrix that delivers the acidic treatment benefits while reducing direct skin irritation and sting discomfort, acting as a buffer between the harsh low pH environment and the sensitive skin.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Lightly- to moderately-crosslinked PVP significantly reduces skin irritation and sting discomfort while maintaining effective thickening and stability in acidic compositions, achieving viscosities of 10,000 cP or more at pH levels as low as 1.3, outperforming traditional thickeners.
Implementation Method 1
lightly- to moderately-crosslinked PVP effectively and quite elegantly thickens topical compositions having a personal care or pharmaceutical acid, even at a low pH of 6 or less, or very low pHs of 4 or less, or even extremely low pHs of 2 or less
Data Source
AI summary
Topical compositions are provided that have 0.5% or more of at least one personal care or pharmaceutical acid, and lightly- to moderately-crosslinked PVP, which is an effective thickener in the low pH systems. In preferred embodiments, the acid is a hydroxy acid and the composition used for personal care, or prescriptive or non-prescriptive medication indications for use on the skin, hair, scalp, foot, or lips. Also provided is the use of the topical compositions to deliver the acid(s) to the skin, hair, scalp, foot, or lips. Especially preferred is a use to reduce irritation and stinging compared to an equivalent compositions not having lightly- to moderately-crosslinked PVP.