Patent ID: 7294297

Claim:
A method for producing a bristle from a thermoplastic polymer by injection molding a molten polymer mass into a bristle molding channel, said channel having a predetermined length and a predetermined cross sectional shape along said length, the method comprising the steps of: (a) injecting the molten polymer mass into said channel under pressure, said pressure being selected in dependence on said cross sectional shape of said channel, a ratio of a largest width of a cross section of said channel to said length of said channel being selected as less than or equal to 1:10, wherein said injection pressure is 2000 to 5000 bar (2×10 5 kPa to 5×10 5 kPa), and sufficient to provide a specific pressure in a bristle forming channel of more than 300 bar (0.3×10 5 kPa); and b) venting said channel along said length during step a), wherein a shear flow is established with a core speed of approximately 1000 mm/s in a center of molten polymer mass flow and with a large shearing effect due to wall friction of the molten polymer mass under distinct longitudinal orientation of polymer molecules, at least in a portion of the molten polymer mass proximate a wall of said channel, said longitudinal orientation of the polymer molecules being maintained throughout said length of said channel.