Process for producing microporous tubes of polytetrafluoroethylene
AssigneeSumitomo Electric Industries, Ltd.
InventorKoichi Okita
Life of this patent
Estimating the term…
Abstract
Polytetrafluoroethylene resin tubes having small pore size and high porosity are produced by a process which includes stretching the tubes by drawing using a metal die and a metal plug. By using the die and plug, the stress necessary for stretching is converted to a compressive force in the thickness direction of the tube. This compressive force is an essential factor in producing the microporous structure of the tubes. In addition, when stretching is performed by drawing, a ratio of thickness to inside diameter of the tube of 0.07 or less can be easily achieved.
Claims3
A process for producing microporous tubes which comprises
- molding a polytetrafluoroethylene resin containing a liquid lubricating agent by a paste method to form a tube,
- removing the liquid lubricating agent,
- stretching by drawing the tube in a lengthwise direction using a die and a plug, and
- sintering at a temperature of about 327.degree. C. or more
- whereby as a result of said stretching and said drawing, a microporous tube is produced having a porosity and a bubble point in a range between the point A, B, C and D defined in the following table;
- ______________________________________ porosity bubble point ______________________________________ A 96% 0.02 kg/cm.sup.2 B 54% 2.0 kg/cm.sup.2 C 20% 2.0 kg/cm.sup.2 D 30% 1.0 kg/cm.sup.2 ______________________________________
- and having a ratio of wall thickness to inside diameter of about 0.1 or less.
Dependencies are inferred from the claim text.