Process For Manufacturing a Ptfe Filament, and a Ptfe Filament, and a Ptfe Filament Obtained By This Process

Abstract

The present invention consists of an inventive process for manufacturing a PTFE filament ( 7 ) of the type comprising steps of extrusion, and, subsequently, stretching, heating and cutting, and an inventive PTFE filament obtained by this process, are provided. The process of the present invention comprises the following steps prior to extrusion providing a recipient, which preferably consists of a cylinder ( 1 ) of pre-form machine, having rigid side walls; arranging a first mixture (A) containing PTFE filler, and a second mixture (B) containing PTFE, inside the recipient, side by side and aligned with the side walls; and pressing the first and second mixtures in a direction parallel to the side walls to form a billet ( 5 ) in which the first and second mixtures (A, B) have different coefficients of friction. After these steps, the billet ( 5 ) is extruded to form a strand ( 6 ), which is subsequently stretched, heated, rolled and cut by known processes in the art to form the inventive PTFE filament, which comprises one side with a filler and the other side without filler, so that these sides have different coefficients of friction. Also, in a preferred embodiment, the filament presents each side with a different color.

1 . A process for manufacturing a PTFE filament of the type comprising steps of extrusion, and, subsequently, stretching, heating and cutting PTFE, characterized by the following steps prior to extrusion:
 providing a recipient having rigid side walls;   arranging a first mixture containing PTFE and a filler, and a second mixture containing PTFE, inside the recipient, side by side and aligned with the side walls; and   pressing the first and second mixtures in a direction parallel to the side walls to form a billet in which the first and second mixtures have different coefficients of friction.   
     
     
         2 . The process according to  claim 1  is characterized by the fact that, in the arranging step, the first and the second mixtures are inserted respectively into two portions of the recipient separated by a barrier, and, subsequently, the barrier is removed, enabling a part of the first mixture to contact a part of the second, and be arranged side by side and aligned with the side walls of the recipient. 
     
     
         3 . The process according to  claim 1  or  2  is characterized by the fact that, in the step of arranging, the first mixture includes a pigment and the second mixture includes another pigment. 
     
     
         4 . A PTFE filament obtained by the process defined in  claim 1  is characterized by comprising one side with a filler, so that this side has a different coefficient of friction in relation to the other side. 
     
     
         5 . The PTFE filament in  claim 4  is characterized by the fact that the first and the second mixtures have the same shrink properties. 
     
     
         6 . The PTFE filament in  claim 4  or  5  is characterized by further comprising a lubricant. 
     
     
         7 . The PTFE filament in any one of  claims 4  to  6  is characterized by the fact that each side has a different color. 
     
     
         8 . The PTFE filament in any one of  claims 4  to  7  is characterized by the fact that the filler comprises at least one of silica, alumina, mica and calcium carbonate. 
     
     
         9 . The PTFE filament according to any one of  claims 4  to  8  is characterized by the fact that the quantity of filler in the respective side ranges from 1 to 25%. 
     
     
         10 . The PTFE filament according to any one of  claims 4  to  9  is characterized by the fact that the quantity of pigment in at least one side ranges from 0.05% to 10%. 
     
     
         11 . The PTFE filament according to any one of  claims 4  to  10  is characterized by the fact that said coefficient of friction in the side with filler ranges from 0.08 to 0.20 and the other side is less than 0.08. 
     
     
         12 . The PTFE filament according to any one of  claims 4  to  11 , characterized by comprising a width ranging from 0.5 to 3.0 mm, a thickness ranging from 20 to 400 μm, a density ranging from 0.7 to 2.2 g/cm3, a tensile strength ranging from 100 to 1100 MPa and a tenacity ranging from 2.0 to 6.0 cN/dtex.