480 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (d) Have a protective colloid and surfactant effect. (e) Water-susceptibility can be controlled. Acrylic thickeners could be of interest, for instance, in shampoos. The effect of a commercial acrylic thickener on an aqueous sodium poly- oxyethylene lauryl sulfate solution (Cycloryl NA), suggested as a base for shampoos, is compared in Fig. 4 with methyl cellulose and sodium chloride. Cosmetic products in which synthetic resins have made most progress appear to be hair sprays, in which materials such as vinyl pyrrolidone- vinyl acetate copolymers have distinct advantages over shellac (16). Vinyl acetate-crotonic acid and methyl vinyl ether-ethyl hydrogen maleate copolymers have also been suggested (17). These products are normally alkali-soluble and could be considered as thickeners in other contexts, but in hair sprays they are useful for their cognate property of removability with mild aqueous alkali. The methacrylate copolymer types described above would fit in naturally for this type of application except for the fact that large quantities of water cannot, it appears, be tolerated in hair sprays. It would, therefore, be a prerequisite either to convert the emulsion polymer into a dry form or prepare it directly in a suitable solvent. ACKNOWLEDGEMENTS Most of the experimental work was carried out by I. D. Lewis and S. F. Rickaby, to whom grateful thanks are due. (Received: 17th July 1969) REFERENCES (1) German Pat. 540 101 (2) US Pat. 2 643 245/6. (3) US Pat. 2 263 598. (4) Fordyce, D. B., Dupre, J. and Toy, W. Off. Dig., 31 284 (1959). (5) Brit. Pat. 856 403. (6) Davies, R. F. B. and Reynolds, G. E. J. J. Appl. Polymer Sci., 19, 47 (1968). (7) King, A. P. and Naidus, H. J. Polymer Sci. C., No. 27 311 (1969). (8) Atherton E. and Peters, R. H. J. Soc. Leather Trades Chemists, 38 22 (1954). (9) Issacs, P. K. and Edelhauser, H. A. J. Appl. Polymer Sci., 10 171 (1966). (10) Gulbekian, E. V. and Sweetingham, M. J. Proc. Vth Intern. Congr. Surface Activity, 9, 965 (Barcelona 1968). (11) Muroi, S., Hosoi K. and Ishikawa, T. J. Appl. Polymer Sci., 11 1963 (1967). (12) Wesslau, H. Makrotool. Chem., 69 220 (1963). (13) Stone-Masui J. and warilion, A. J. Colloid Interf. Sci., 28 187 (1968). (14) Canad. Pat. 807 127. (15) Chemical Week, 154 (21st June, 1969). (16) Root, M. J. Am. Perfumer, 75 43 (10, 1960) (17) Root, M. J. and Bohac, S. Soap Che•n. Specialties, 41 95 (2, 1965).

ALKALI-THICKENABLE METHACRYLATE COPOLYMER EMULSIONS 481 DISCUSSION MR. C. PUGH: HOW do these polymers compare with other film formers in hair- sprays in respect of flexibility and adhesion? THE LECTURER: The advantage of this type of system is that by varying the polymer composition one can get a wide range of properties, particularly by adjusting the number of acid groups in the polymer chain. Film formation can be varied by the polymer type it can be powdery, sticky or in between. MR. R. L. DAW•S: Could you say a word about sensitivity to electrolytes insofar as the viscosity of these materials is concerned? TH• LEC'rUR•R: The effect of adding up to 20•o NaC1 to a n-BMA: methacrylic acid (60:40) copolymer was an increase of the viscosity. Different types of electrolytes are likely to have different effects. Thus, Markovitz and Kimball (18) found a re- duction in viscosity on addition of NaCI to sodium polyacrylate solution. MR. R. L. DAWES: How does the effect vary with the valency of the added metal ion? TH• LECTURER: It is possible that some of these products would precipitate if di- or trivalent metal cations were added. Some work on this has been carried out by Proshliakova, Zubov and Kargin (19). I I o •ooo 2ooo 3ooo Shear stress, N m -2 Figure $ Shirley-Ferranti flow curve (medium cone 60 s sweep time X5 range factor) at 25øC. n-Butyl methacrylate: methacrylic acid (60:40) copolymer emulsion at high pH non-volatile = 7.52 •o. (18) Markovitz, H. and Kimball, G. E. f. Colloid Sci., 5 115 (1950). (19) Proshliakova, N. F., Zubov, P. I. and Kargin, V. A. Kolloid. Zh., 9•0 199 (1958).