Raw material basis for the mass production of chemical fibres has not been changed for years. The group of the predominating fibre-forming synthetics i.e. polyester and polyamide was extended within the last decade with polypropylene. Modification of such raw materials allows for production of fibres with more attractive properties. The more common method of obtaining fibres with improved properties relies on introducing special additives into a fibre-forming material. Especially in case of polypropylene which is unreceptive to any chemical modification. Modifying agents introduced into melt spun synthetic fibres must comply with the basic condition i. e. they must be thermostable at the spinning temperature equal to over 200℃. In case of solid substances that do not undergo melting at the spinning temperature their granulation is also very important. Fibre-forming polymers should not contain any solid particles larger than 5㎛ : most favorably less than 2㎛. Such a precondition is met by traditional components applied in order to modify luster and colour of fibres i.e. titanium dioxide, carbon black, pigments. Nevertheless, the majority of modifying agents introduced into fibres when improving some utility properties of fibres at the same time impair their other properties, first of all mechanical properties of fibres. Optimisation in respect of the quantity of modifying agent introduction constitutes always a very important stage of research. Besides the technological aspect it is also very important from the economic point of view as many modifying agent are very expensive