Tosylamide/formaldehyde resin

Tosylamide/formaldehyde resin (TSFR) is a polymeric resin used as a plasticizer and secondary film-forming agent in nail polishes. While it was still in use as of 2023,^[update] its use has been diminishing in favor of hypoallergenic alternatives, due to the prevalence of reactions causing allergic contact dermatitis of the eyelids, face, and neck.

Tosylamide/formaldehyde resin

Names
Systematic IUPAC name poly[4-methylbenzenesulfonamide-alt-methanal]
Other names Toluenesulfonamide/formaldehyde resin Formaldehyde-p-toluenesulfonamide copolymer Santolite MHP Santolite MS
Identifiers
CAS Number	25035-71-6
ECHA InfoCard	100.132.132
EC Number	607-493-7
PubChem CID	159985
CompTox Dashboard (EPA)	DTXSID80933988
Properties
Chemical formula	(C8H9NO2S)n (n ≤ 10)
Molar mass	Variable (400–1900 g·mol−1)
Melting point	82 °C (180 °F; 355 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Production

TSFR is produced by condensing p-tosylamide [de] (often impure, containing o-tosylamide [de]) with formaldehyde. It consists of a mixture of short oligomers with repeating unit −N(Ts)CH₂−, terminated by −NHTs or −N(Ts)CH₂OH groups.^[2]

Allergenicity

Nail polishes containing TSFR were first introduced in 1939, becoming a major cause of allergic contact dermatitis of the eyelids, face, and neck.^[3][4] Allergic responses are caused by the water-soluble contaminants 5-tosyl-1,3,5-dioxazinane (TsN(−)(CH₂OCH₂OCH₂−)) and 3,5-ditosyl-1,3,5-oxadiazinane (TsN(−)(CH₂N(Ts)CH₂OCH₂−)), rather than formaldehyde, which is only present in trace quantities (<0.5%).^[3][4][5]

Since the early 2010s, the prevalence of allergic reactions to TSFR has decreased, due to the widespread use of hypoallergenic alternatives such as tosylamide/epoxy resin (first introduced in the late 1980s^[6]), cellulose acetate butyrate, and polyester resins (e.g. 2,2,4-Trimethyl-1,3-pentanediol [de]–isophthalic acid–trimellitic anhydride).^[7]