Method for manufacturing a fibrous material impregnated with thermoplastic polymer

A method for manufacturing an impregnated fibrous material comprising a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, wherein said impregnated fibrous material is produced as a single unidirectional ribbon or a plurality of unidirectional parallel ribbons and wherein said method comprises a step of pre-impregnating said fibrous material in the form of a roving or several parallel rovings with a thermoplastic polymer of the at least one thermoplastic polymer matrix, and at least one step of heating the thermoplastic polymer matrix making it possible to melt, or maintain in the molten state, said thermoplastic polymer after pre-impregnation,

• the at least one heating step being carried out by means of at least one heat-conducting supporting part (E) and at least one heating system, with the exception of a heating calender,
• said at least one supporting part (E) being temperature-controlled at a temperature, when the thermoplastic polymer is a thermoplastic semi-crystalline polymer, of Tc to Tm+50° C. of said thermoplastic polymer, and when the thermoplastic polymer is an amorphous polymer, of Tg+50° C. to Tg+250° C. of said thermoplastic polymer, wherein Tc is a crystallization temperature, Tm is a melting temperature, and Tg is a glass transition temperature,
• said roving or rovings being in contact with all or part of the surface of said at least one supporting part (E) and partially or wholly passing over the surface of the at least one supporting part (E) present at the level of the heating system,
• and the porosity level in said pre-impregnated fibrous material being less than 10%.