The effect of reactive dyes upon the uptake and anti bacterial action of poly(hexamethylene biguanide) on cotton. Part 2: Uptake of poly(hexamethylene biguanide) on cotton dyed with β-sulphatoethylsulphonyl reactive dyes

Polyhexamethylene biguanide (PHMB) is a widely used bacteriocide. It is marketed as an aqueous solution of its hydrochloride from which it is readily adsorbed onto cotton, this process depending upon the ability of the cationic PHMB to form electrostatic links with the anionic carboxylate groups present on cotton. The introduction of chemically bound sulphonic acid groups into cotton, which takes place during the process of dyeing with reactive dyes, increases the capacity of cotton to take up PHMB. The saturation levels of PHMB on un-dyed cotton, and cotton dyed individually with a trichromat of warm dyeing dyes, has been measured. Additionally, the effective agent contents of the dyes and their percentage fixation on to the cotton were determined, thus allowing the concentration of sulphonic acid groups present on the cotton to be calculated. From this and knowledge of the saturation value of PHMB on dyed and un-dyed cotton the stoichiometry of the interaction between PHMB and sulphonic acid groups was deduced. For the disulphonated dye, C I Reactive Black 5, each sulphonic acid group appeared to be associated with uptake of an additional 1.12 equiv. of monomeric biguanide unit. For the monosulphonated dyes, C I Reactive Orange 16 and C I Reactive Orange 107, the corresponding values were 1.31.and 1.47, respectively.