US 11,890,797 B2
Method for preparing unsintered polytetrafluoroethylene film and porous film thereof
Katsutoshi Yamamoto, Osaka (JP); Michiko Sawai, Osaka (JP); Asami Masuda, Osaka (JP); and Shigemi Oikawa, Osaka (JP)
Assigned to CHONGQING BOMAN NEW MATERIAL CO., LTD., Chongqing (CN)
Appl. No. 17/294,512
Filed by CHONGQING BOMAN NEW MATERIAL CO., LTD., Chongqing (CN)
PCT Filed Nov. 11, 2019, PCT No. PCT/JP2019/044134
§ 371(c)(1), (2) Date May 17, 2021,
PCT Pub. No. WO2020/100811, PCT Pub. Date May 22, 2020.
Claims priority of application No. 2018-214816 (JP), filed on Nov. 15, 2018.
Prior Publication US 2021/0402665 A1, Dec. 30, 2021
Int. Cl. B29C 48/00 (2019.01); B29C 43/24 (2006.01); B29C 55/06 (2006.01); B29C 71/02 (2006.01); C08J 5/18 (2006.01); B29C 71/00 (2006.01); B29C 55/12 (2006.01); B29C 55/02 (2006.01); B29K 27/18 (2006.01); B29C 67/04 (2017.01)
CPC B29C 48/0011 (2019.02) [B29C 43/24 (2013.01); B29C 48/002 (2019.02); B29C 48/0018 (2019.02); B29C 55/023 (2013.01); B29C 55/06 (2013.01); B29C 55/12 (2013.01); B29C 71/0009 (2013.01); B29C 71/02 (2013.01); C08J 5/18 (2013.01); B29C 67/04 (2013.01); B29K 2027/18 (2013.01); C08J 2327/18 (2013.01)] 5 Claims
 
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.