Patent ID: 11890797
Assignee: CHONGQING BOMAN NEW MATERIAL CO., LTD.
Field: Other special machines (Mechanical engineering)
Classification: CPC B  C | IPC B  C

Claim 0:
1. A method for preparing an unsintered polytetrafluoroethylene film, the method comprising:
making a mixture by adding a forming aid to polytetrafluoroethylene fine powder obtained by emulsion polymerization of tetrafluorethylene,
filling the mixture in an extrusion forming die, and extruding the filled mixture from the extrusion forming die to produce an extrusion forming body,
calendering the extrusion forming body into a film shape with a roll to produce a forming aid-removed film without the forming aid,
providing two rolls composed of a pair of rollers with one made of metal and the other made of rubber with D type hardness more than 80 as measured by JIS K 6253 coated on a metal shaft core, and
pinching the forming aid-removed film the rolls at room temperature and compressing the forming aid-removed film with a linear pressure of 50 kg/cm-200 kg/cm so that thickness of the forming aid-removed film is reduced at a reduction rate more than 24.6% and the density is 2.0 g/cm3.