j. Soc. Cosmet. Chem. 22 27-41 (1971) (•) 1971 Society of Cosmetic Chemists of Great Britain Polymer evolution--from to synthetic natural R. S. McKEE and N.M. MORSS* Presented at the Symposium on "Gums and Thickeners", organised by the Society of Cosmetic Chemists of Great Britain, at Oxford, on 14th October 1969. Synopsis---The reasons for the displacement of NATURAL GUMS and thickeners by semi- synthetic and wholly SYNTHETIC POLYMERS are briefly discussed and exemplified by the CELLULOSE ETHER range and COPOLYMERS of METHYL VINYL ETHER and MALEIC ANI-IYDRIDE. It is indicated that the latter materials should find a wide application in GELS, CREAMS and AEROSOL HAIRSPRAYS. INTRODUCTION From earliest times, starch, animal glue, casein and other natural products have been used as water soluble binders and thickeners in cosmetic preparations. In more recent years the alginates and chemically modified starches and cellulose have been added to this list together with completely synthetic products such as polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide and carboxyvinyl polymers. The present paper com- pares the properties of a few of these older materials with those of a new family of coplymers based on methyl vinyl ether and maleic anhydride. NATURAL GUMS AND THICKENERS The natural gums and thickeners usually have some unique rheological or other property which makes them almost ideal for the preparations in *Nobel Division, Imperial Chemical Industries Ltd., Stevenston, Ayrshire. 27

28 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS which they are used. On the other hand, as is natural considering their source, their purity, colour and reproducibility tend to be variable and, possibly more important, world prices show a tendency to rise faster than those of synthetic materials. The chemist therefore has considerable in- centive to try to make semi-synthetic or fully synthetic water soluble polymers which match or improve on the properties of the natural polymers. SEMI-SYNTHETIC POLYMERS The cellulose ethers are perhaps the best known examples of semi- synthetic polymers. Etherifying agents are used under controlled con- ditions to confer water solubility on a rigorously purified cellulose of known molecular weight. By varying the molecular weight of the cellulose and the type and quantity of etherifying agent, a wide variety of properties can be obtained. The behaviour of almost any natural gum can be simulated, while a number of products with useful new properties have been evolved. As is well-known, cellulose ethers have found a place in a number of cosmetic and pharmaceutical preparations such as hand lotions and slim- ming aids. Perhaps the most outstanding success of cellulose ethers in this field has, however, been the displacement of carragheenates as the thickener in toothpaste. Here it was found that sodium carboxymethyl cellulose (SCMC) had advantages in colour, reproducibility and cost, but these factors alone would not have been sufficient it was necessary also that the chemist should find a way of controlling the degree of thixotropy developed by the SCMC in solution the toothpaste must be thin enough when made to be poured into tubes, and then thicken up on storage to give the soft gelled structure familiar to all. A typical simple formulation might be: Parts by weight SCMC (Edifas BX100)• 0.90 Glycerol 25.00 1)icalcium Phosphate 42.00 Chalk (Premium Grade) 5.00 Sodium lauryl sulphate 1.50 Sacchari,t 0.10 Preservative 0.10 Flavour 0.75 Water and other ingredients 24.65