Novel enhancing silicone copolymer introduced

Manufacturers of personal care products are on an eternal quest to formulate topical compositions that provide superior film properties on keratinous surfaces with exceptional aesthetics. The ideal cosmetic film must be easily applied and dry quickly, have a natural appearance without looking artificial, permit the underlying skin to breathe and retain moisture, and, most importantly, have a feel that is soft, cushiony, powdery and silky, resulting in younger looking skin. In the mid 1900s, the emergence of silicones in personal care formulations ushered in a new technology to achieve most of the above claims. As silicone technology advanced, new materials emerged that gave an entirely different feel as well as performance properties on skin and hair. One silicone in particular is widely used in personal care products because of the exceptional aesthetics it provides to cosmetic formulations: dimethicone crosspolymer elastomer. This is a “cyclised dimethicone” which means an organosiloxane comprised of repeating siloxane [-Si-O-Si-O-] units with hydrocarbon side chain groups, crosslinked internally with a carbon based moiety. Numerous patents disclose the use of dimethicone crosspolymers and related elastomers in a wide range of personal care and related applications. For example, Chesebrough/Unilever (US Patent 5,833,973) teaches the use of various crosslinked, elastomeric silicones in aqueous-based skin care formulations where “a unique, powdery feel” was claimed. Revlon (US Patent 6,171,581) teaches the use of silicone elastomers in water/oil emulsions used in solid antiperspirant and deodorant applications. Also Wella (US Patent 6,488,918) teaches the use of silicone crosspolymer elastomers to produce a range of “powdery cosmetic compositions” for hair treatment applications. These are only a handful of the many silicone crosspolymer elastomer application patents. Due to the sheer numbers, the crosspolymer application patent landscape can be confusing and often limit use in personal care products. The myriad of crosspolymer use patents in skin care, colour, sun care and hair care has created a need to develop an alternative polymer with similar properties to silicone elastomer crosspolymers which would minimise patent infringement concerns. A new silicone polymer without crosslinking groups has emerged which provides similar attributes as crosspolymer elastomers with additional application benefits due to unique structures. Recently patented (US Patent 7,407,666 with other patents pending) bis-vinyl dimethicone/dimethicone copolymer (BVDD) affords the formulation chemist an alternative to crosslinked silicones for developing aesthetically pleasing cosmetics while minimising the possibility of patent infringement. Discussions with numerous formulators in recent years directed JEEN to the research that resulted in the development of the patented BVDD, which has been trademarked the Jeesilc PS Series of silicone copolymers. The trends identified from discussions indicated there was a need for a silicone-based chemistry with wider applicability and greater formulating flexibility, while at the same time providing similar feel as crosslinked silicone polymers.

Copolymer description

Figure 1 illustrates how these copolymers are synthesised from linear silanic hydrogen polymers and linear vinylsiloxanes. As compared to crosspolymer elastomers, these copolymers have no crosslinking groups. In forming the novel BVDD copolymer, the silanic hydrogen compound (A in Fig. 1) and a terminal di-vinyl silanic hydrogen compound (B in Fig. 1) first form the continuous polymer chain (AB in Fig. 1) of varying chain lengths. It has been found that the copolymer chain length is solvent dependent – the larger molecular weight chains can be formed in hydrocarbons, whereas the smaller chains are most often formed in cyclomethicone solvents. While other theories are possible, we believe that as the polymer molecular weight increases, the terminal vinyl group and the terminal silanic hydrogen group on the same polymer bond via a reaction often referred to as “backbiting”, form a cyclic BVDD copolymer structure as illustrated in Figure 2.