Method for producing a pleatable textile structure having electrostatically charged fibres, preferably for use as a filter material for an electret filter, where a die arrangement is used in the method and is constructed of at least two separate die bars, where at least the first die bar has concentric orifices, and a first polymer is spun into fibres of a first fibre type by means of the first die bar, and a second polymer is spun into fibres of a second fibre type by means of the second die bar, where the fibres of the first and second fibre types are spun such that the fibres of the first fibre type have a larger mean fibre diameter than the fibres of the second fibre type, where the mean values of the diameters of the two fibre types have a distance from one another such that two maxima are clearly apparent in the overall distribution of the fibre diameters, where before and/or during the shaping of the textile structure, by means of the collecting device, the fibres of the first fibre type are mixed at least in regions with the fibres of the second fibre type, and the fibres of the first fibre type and/or the fibres of the second fibre type, at least during fibre-forming and/or during drawing, are treated with a polar liquid, the fibres being thereby charged electrostatically, where before and/or during the shaping of the textile structure the fibres of the first fibre type are mixed with the fibres of the second fibre type in such a way that, at least in a part-volume of the textile structure, the proportions of the fibres of the first fibre type and of the fibres of the second fibre type exhibit a gradient profile over the cross section of the textile structure, the gradient preferably being formed such that on the side of the nonwoven which is to be disposed on the inflow side in the filter, the proportion of the coarser fibres is higher than the proportion of the finer fibres, and on the side which is to be disposed on the outflow side, the proportion of the finer fibres is higher than the proportion of the coarser fibres. and a first polymer is spun into fibres of a first fibre type by means of the first die bar, and a second polymer is spun into fibres of a second fibre type by means of the second die bar, where the fibres of the first and second fibre types are spun such that the fibres of the first fibre type have a larger mean fibre diameter than the fibres of the second fibre type, where the mean values of the diameters of the two fibre types have a distance from one another such that two maxima are clearly apparent in the overall distribution of the fibre diameters, where before and/or during the shaping of the textile structure, by means of the collecting device, the fibres of the first fibre type are mixed at least in regions with the fibres of the second fibre type, and the fibres of the first fibre type and/or the fibres of the second fibre type, at least during fibre-forming and/or during drawing, are treated with a polar liquid, the fibres being thereby charged electrostatically, where before and/or during the shaping of the textile structure the fibres of the first fibre type are mixed with the fibres of the second fibre type in such a way that, at least in a part-volume of the textile structure, the proportions of the fibres of the first fibre type and of the fibres of the second fibre type exhibit a gradient profile over the cross section of the textile structure, the gradient preferably being formed such that on the side of the nonwoven which is to be disposed on the inflow side in the filter, the proportion of the coarser fibres is higher than the proportion of the finer fibres, and on the side which is to be disposed on the outflow side, the proportion of the finer fibres is higher than the proportion of the coarser fibres.