Ptfe powder and method of producing ptfe powder for molding

Abstract

This invention provides a polytetrafluoroethylene powder capable of giving moldings which are improved in surface roughness Ra, tensile strength and/or tensile elongation as compared with the prior art ones and can be excellent in dielectric breakdown strength and, further, can be excellent, if desired, in apparent density and/or powder flowability as well, and a method of producing a polytetrafluoroethylene molding powder. The present invention is a PTFE powder wherein a surface roughness Ra of molded articles a1 for measurement is less than 0.92 μm.

1 . A polytetrafluoroethylene powder 
 wherein a surface roughness Ra of molded articles a1 for measurement is less than 0.92 μm.    
     
     
         2 . A polytetrafluoroethylene powder 
 wherein an apparent density is not lower than 0.45 g/cm 3  and a surface roughness Ra of molded articles a1 for measurement is less than 1.9 μm.    
     
     
         3 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times and a surface roughness Ra of molded articles a1 for measurement is less than 1.9 μm.    
     
     
         4 . The polytetrafluoroethylene powder according to  claim 3 , 
 wherein the surface roughness Ra of molded articles a1 for measurement is less than 1.6 μm.    
     
     
         5 . The polytetrafluoroethylene powder according to  claim 3 , 
 wherein the surface roughness Ra of molded articles a1 for measurement is less than 1.2 μm.    
     
     
         6 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times, an apparent density is not lower than 0.45 g/cm 3  and a surface roughness Ra of molded articles a1 for measurement is less than 1.9 μm.    
     
     
         7 . The polytetrafluoroethylene powder according to  claim 6 , 
 wherein the apparent density is not lower than 0.6 g/cm 3  and the surface roughness Ra of molded articles a1 for measurement is less than 1.6 μm.    
     
     
         8 . The polytetrafluoroethylene powder according to  claim 7 , 
 wherein the surface roughness Ra of molded articles a1 for measurement is less than 1.2 μm.    
     
     
         9 . A polytetrafluoroethylene powder 
 wherein an apparent density is not lower than 0.45 g/cm 3  and a breakdown voltage of molded articles a2 for measurement is not lower than 9.1 kV.    
     
     
         10 . The polytetrafluoroethylene powder according to  claim 9 , 
 wherein the breakdown voltage of molded articles a2 for measurement is not lower than 12 kV.    
     
     
         11 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times and a breakdown voltage of molded articles a2 for measurement is not lower than 9.1 kV.    
     
     
         12 . The polytetrafluoroethylene powder according to  claim 11 , 
 wherein the breakdown voltage of molded articles a2 for measurement is not lower than 10 kV.    
     
     
         13 . The polytetrafluoroethylene powder according to  claim 11 , 
 wherein the breakdown voltage of molded articles a2 for measurement is not lower than 12 kV.    
     
     
         14 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times, an apparent density is not lower than 0.45 g/cm 3  and a breakdown voltage of molded articles a2 for measurement is not lower than 9.1 kV.    
     
     
         15 . The polytetrafluoroethylene powder according to  claim 14 , 
 wherein the breakdown voltage of molded articles a2 for measurement is not lower than 10 kV.    
     
     
         16 . The polytetrafluoroethylene powder according to  claim 14 , 
 wherein the breakdown voltage of molded articles a2 for measurement is not lower than 12 kV.    
     
     
         17 . A polytetrafluoroethylene powder 
 wherein a tensile strength of molded articles a3 for measurement is not lower than 58.7 MPa.    
     
     
         18 . A polytetrafluoroethylene powder 
 wherein a tensile elongation of molded articles a3 for measurement is not less than 556%.    
     
     
         19 . A polytetrafluoroethylene powder 
 wherein an apparent density is not lower than 0.45 g/cm 3  and a tensile elongation of molded articles a3 for measurement is not less than 431%.    
     
     
         20 . A polytetrafluoroethylene powder 
 wherein a surface roughness Ra of molded articles a1 for measurement is less than 1.5 μm and a tensile strength of molded articles a3 for measurement is not lower than 47.8 MPa.    
     
     
         21 . A polytetrafluoroethylene powder 
 wherein a surface roughness Ra of molded articles a1 for measurement is less than 1.2 μm and a tensile elongation of molded articles a3 for measurement is not less than 423%.    
     
     
         22 . A polytetrafluoroethylene powder 
 wherein an apparent density is not lower than 0.45 g/cm 3 , a surface roughness Ra of molded articles a1 for measurement is less than 2.4 μm and a tensile elongation of molded articles a3 for measurement is not less than 370%.    
     
     
         23 . The polytetrafluoroethylene powder according to  claim 22 , 
 wherein the surface roughness Ra of molded articles a1 for measurement is less than 1.9 μm and the tensile elongation of molded articles a3 for measurement is not less than 400%.    
     
     
         24 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times, a surface roughness Ra of molded articles a1 for measurement is less than 2.4 μm and a tensile elongation of molded articles a3 for measurement is not less than 370%.    
     
     
         25 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times, an apparent density is not lower than 0.45 g/cm 3 , a surface roughness Ra of molded articles a1 for measurement is less than 2.4 μm and a tensile elongation of molded articles a3 for measurement is not less than 370%.    
     
     
         26 . The polytetrafluoroethylene powder according to  claim 25 , 
 wherein the apparent density is not lower than 0.6 g/cm 3 .    
     
     
         27 . A polytetrafluoroethylene powder 
 wherein a surface roughness Ra of molded articles a1 for measurement is less than 0.92 μm and a breakdown voltage of molded articles a2 for measurement is not lower than 10 kV.    
     
     
         28 . A polytetrafluoroethylene powder 
 wherein an apparent density is not lower than 0.45 g/cm 3 , a surface roughness Ra of molded articles a1 for measurement is less than 2.5 μm and a breakdown voltage of molded articles a2 for measurement is not lower than 8.5 kV.    
     
     
         29 . The polytetrafluoroethylene powder according to  claim 28 , 
 wherein the apparent density is not lower than 0.6 g/cm 3 .    
     
     
         30 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times, a surface roughness Ra of molded articles a1 for measurement is less than 2.5 μm and a breakdown voltage of molded articles a2 for measurement is not lower than 8.5 kV.    
     
     
         31 . The polytetrafluoroethylene powder according to  claim 30 , 
 wherein the surface roughness Ra of molded articles a1 for measurement is less than 1.9 μm and the breakdown voltage of molded articles a2 for measurement is not lower than 9.1 kV.    
     
     
         32 . A polytetrafluoroethylene powder 
 wherein a flowability is not less than 0.5 times, an apparent density is not lower than 0.45 g/cm 3 , a surface roughness Ra of molded articles a1 for measurement is less than 2.5 μm and a breakdown voltage of molded articles a2 for measurement is not lower than 8.5 kV.    
     
     
         33 . The polytetrafluoroethylene powder according to  claim 32 , 
 wherein the apparent density is not lower than 0.6 g/cm 3 .    
     
     
         34 . A polytetrafluoroethylene powder 
 wherein a tensile strength of molded articles a3 for measurement is not lower than 47.8 MPa and a tensile elongation of molded articles a3 for measurement is not less than 451%.    
     
     
         35 . A polytetrafluoroethylene powder 
 wherein a breakdown voltage of molded articles a2 for measurement is not lower than 11.5 kV and a tensile strength of molded articles a3 for measurement is not lower than 47.8 MPa.    
     
     
         36 . A polytetrafluoroethylene powder 
 wherein a breakdown voltage of molded articles a2 for measurement is not lower than 10 kV and a tensile elongation of molded articles a3 for measurement is not less than 556%.    
     
     
         37 . A polytetrafluoroethylene powder 
 wherein a surface roughness Ra of molded articles a1 for measurement is less than 1.2 μm, a tensile strength of molded articles a3 for measurement is not lower than 47.8 MPa and a tensile elongation of molded articles a3 for measurement is not less than 423%.    
     
     
         38 . A polytetrafluoroethylene powder 
 wherein a breakdown voltage of molded articles a2 for measurement is not lower than 10 kV, a tensile strength of molded articles a3 for measurement is not lower than 47.8 MPa and a tensile elongation of molded articles a3 for measurement is not less than 451%.    
     
     
         39 . A method of producing a polytetrafluoroethylene molding powder by pulverizing an unpulverized polytetrafluoroethylene powder 
 wherein said unpulverized polytetrafluoroethylene powder comprises a polytetrafluoroethylene-based polymer obtained by suspension polymerization,    said polytetrafluoroethylene-based polymer comprises a not-modified polytetrafluoroethylene and/or a modified polytetrafluoroethylene and    said pulverization is carried out without causing substantial fibril-formation on a resulting particle.    
     
     
         40 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the polytetrafluoroethylene-based polymer is the not-modified polytetrafluoroethylene and    said polytetrafluoroethylene-based polymer has an amorphous index of not less than 0.25.    
     
     
         41 . The method of producing a polytetrafluoroethylene molding powder according to  claim 40 , 
 wherein the amorphous index is 0.3 to 0.4.    
     
     
         42 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the polytetrafluoroethylene-based polymer is the modified polytetrafluoroethylene and said polytetrafluoroethylene-based polymer shows a heat of crystallization of 18-25 J/g.    
     
     
         43 . The method of producing a polytetrafluoroethylene molding powder according to  claim 42 , 
 wherein the modified polytetrafluoroethylene is obtained by copolymerization of tetrafluoroethylene and a perfluoro(alkylvinylether) and    a mole ratio of said tetrafluoroethylene and said perfluoro(alkylvinylether) [tetrafluoroethylene : perfluoro(alkylvinylether)] is 99:1 to 99.999:0.001.    
     
     
         44 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein an unpulverized polytetrafluoroethylene powder gives an average particle diameter after the pulverization of 1-100 μm.    
     
     
         45 . The method of producing a polytetrafluoroethylene molding powder according to  claim 44 , 
 wherein the average particle diameter is 25-60 μm.    
     
     
         46 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the unpulverized polytetrafluoroethylene powder gives an average particle diameter of 1-25 μm after the pulverization and    the polytetrafluoroethylene-based polymer is the not-modified polytetrafluoroethylene.    
     
     
         47 . The method of producing a polytetrafluoroethylene molding powder according to  claim 40 , 
 wherein the unpulverized polytetrafluoroethylene powder gives an average particle diameter after the pulverization of 1-25 μm.    
     
     
         48 . The method of producing a polytetrafluoroethylene molding powder according to  claim 46 , 
 wherein the average particle diameter is 6-25 μm.    
     
     
         49 . The method of producing a polytetrafluoroethylene molding powder according to  claim 46 , 
 wherein the average particle diameter is 1-6 μm.    
     
     
         50 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the unpulverized polytetrafluoroethylene powder gives an average particle diameter after the pulverization of 1-13 μm and    the polytetrafluoroethylene-based polymer is the modified polytetrafluoroethylene.    
     
     
         51 . The method of producing a polytetrafluoroethylene molding powder according to  claim 42 , 
 wherein the unpulverized polytetrafluoroethylene powder gives an average particle diameter after the pulverization of 1-13 μm.    
     
     
         52 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the pulverization is carried out by an air jet pulverization method.    
     
     
         53 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the pulverization is carried out by a freeze pulverization method.    
     
     
         54 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein the pulverization is carried out by a freeze air jet pulverization method.    
     
     
         55 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein a surface roughness Ra of molded articles a1 for measurement obtained from the polytetrafluoroethylene molding powder is less than 0.92 μm.    
     
     
         56 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein a tensile strength of molded articles a3 for measurement obtained from the polytetrafluoroethylene molding powder is not lower than 58.7 MPa.    
     
     
         57 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein a tensile elongation of molded articles a3 for measurement obtained from the polytetrafluoroethylene molding powder is not less than 556%.    
     
     
         58 . The method of producing a polytetrafluoroethylene molding powder according to  claim 55 , 
 which is further characterized in that a breakdown voltage of molded articles a2 for measurement obtained from the polytetrafluoroethylene molding powder is not lower than 10 kV.    
     
     
         59 . The method of producing a polytetrafluoroethylene molding powder according to  claim 39 , 
 wherein a breakdown voltage of molded articles a2 for measurement obtained from the polytetrafluoroethylene molding powder is not lower than 11.5 kV and a tensile strength of molded articles a3 for measurement obtained from said polytetrafluoroethylene molding powder is not lower than 47.8 MPa.    
     
     
         60 . A polytetrafluoroethylene molding powder obtained by the method of producing a polytetrafluoroethylene molding powder according to  claim 39.