Examples of suitable humectants include: glycerol, polyalkylene glycols, e.g. polyethylene glycol or polypropylene glycol, for instance polyethylene glycol having a weight average molecular weight of from about 200 to 600; neopentyl alcohols such as pentaerythritol or neopentyl glycol; sugar alcohols such as threitol, erythritol, adonitol (ribitol), arabitol, xylitol, dulcitol, mannitol and sorbit