POLYMER EVOLUTION--FROM NATURAL TO SYNTHETIC 35 A typical perfume gel formulation is noted below. Perfume gel Cologne P25656 Propoxylated oleyl alcohol (Provol 10)? Ethanol Water MVE/MA crosslinked (Viscofas X100 000) Tri-is o pro pan o lamin e n-propyl-p-hydroxybenzoate E.D.T.A. Parts by weight 3.10 5.00 61.00 29.50 0.75 0.75 0.01 0.01 The MVE/MA is dispersed in water at 90øC and the mix maintained at this temperature until a slightly viscous, cloudy mucilage is formed. The hydrolised copolymer solution is cooled and mixed into the alcoholic solution of Cologne, propoxylated oleyl alcohol and stabilisers. Finally the mix is gelled by slowly stirring in the alkanolamine. Stability of crosslinked gels Early batches of crosslinked MVE/MA made by I.C.I. gave aqueous and alcohol gels which dropped in viscosity on storage at 50ø( but the latest product has been shown to produce an aqueous gel which maintains a constant viscosity over 7 months at 50øC. Like other water soluble polymers MVE/MA solutions are affected by U.V. light but this can be kept to a minimum by including chelating agents and U.V. absorbers in the formulations. Stabiliser systems which show promise are 8-hydroxyquinoline, thiourea and Cyasorb 2848 together with E.D.T.A. Hair sprays Esters of very low molecular weight MVE/MA copolymer such as the partial butyl ester in isopropanol, Viscofas LBS, or the modified partial ethyl ester, Viscofas LNES, are particularly useful as resins for squeeze pack and aerosol hair sprays. Both resins show excellent compatibility with the Arcton Propellants and their extremely low viscosity being comparable with that of other hair spray resins (Table II) permits aerosols of good spray patterns to be formulated.

36 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Cmnparison of viscosity of typical Viscofas esters with other hair spray resins Resin Low viscosity partial butyl ester MVE/MA (Viscofas LB5) Modified low viscosity partial ethyl ester MVE/MA (Viscofas LNE$) Vinyl acetate-crotonic acid copolymer Vinyl pyrrolidone-vinyl acetate copolymer Parts by weight resin made up to 30 parts with methylated spirit 1.5 1.5 1.5 1.5 Viscosity 25øC cP 3,0 I 2.8 3.7 2.2 The modified ethyl and the butyl esters of MVE/MA are not soluble in water but the hair spray manufacturer can increase the water sensitivity of the lacquer film to give a balance between resistance to high humidity and ease of removal on washing, by simply neutralising part of the remaining free carboxyl groups with an alkanolamine such as 2-amino-2-methyl-1- propanol (AMP). This system is demonstrated in Table III. Table III Effect of AMP neutralisation on water absorption of Viscofas LNE5 fihns Time at oo % RH (h) 1 7 24 48 72 96 •o COOH neutralised by AMP 0 10 120 [40 t 60 80 100 •o water absorbed by ester film 0.8 0.8 1.0 2.8 3.0 3.0 3.4 2.4 3.1 3.9 10.4 13.0 16.8 29.2 3.0 3.8 4.9 13.0 16.3 25.2 34.6 3.6 4.2 6.8 13.6 17.9 25.2 35.0 3.6 4.2 6.8 13.6 19.0 26.8 36.2 3.6 4.2 6.6 13.6 20.4 27.7 37.8 The alkanolamine addition, of course, acts as an internal plasticiser and this must be allowed for in the final aerosol formulation. In Table IV Table IV Effect of AMP content on lacquer hardness COOH neutralised by i Film hardness (% glass) AMP Koenig apparatus 0 77 10 77 20 76 40 72 60 67 80 58 100 5o