Ethylene polymer, stretched molded article, microporous membrane and fiber
The present invention provides an ethylene polymer having a viscosity average molecular weight of 100×10 4 or more and 1,000×10 4 or less, in which a ratio between an isothermal crystallization time at 125° C. and an isothermal crystallization time at 123° C. obtained under specific isothermal crystallization time measurement conditions is 3.5 or more and 10.0 or less, and a degree of crystallization obtained using a differential scanning calorimeter (DSC) is 40% or more and 75% or less.
1. An ethylene polymer, having a viscosity average molecular weight of 100×10 4 or more and 1,000×10 4 or less,
wherein a ratio between an isothermal crystallization time at 125° C. and an isothermal crystallization time at 123° C. obtained under isothermal crystallization time measurement conditions is 3.5 or more and 10.0 or less,
a degree of crystallization obtained using a differential scanning calorimeter (DSC) is 40.0% or more and 75.0% or less, and
said isothermal crystallization time measurement conditions are
1) a temperature is held at 50° C. for 1 minute, and then increased to 180° C. at a temperature increase rate of 200° C./min;
2) the temperature is held at 180° C. for 5 minutes, and then decreased to 122° C. at a temperature decrease rate of 80° C./min;
3) the temperature is held at 122° C. for 5 minutes, and then increased to 180° C. at a temperature increase rate of 200° C./min;
4) the temperature is held at 180° C. for 5 minutes, and then decreased to 123° C. at a temperature decrease rate of 80° C./min;
5) the temperature is held at 123° C. for 10 minutes, and then increased to 180° C. at a temperature increase rate of 200° C./min, wherein the isothermal crystallization time at 123° C. is measured, assuming that a time of reaching 123° C. is a point of origin, 0 min;
6) the temperature is held at 180° C. for 5 minutes, and then decreased to 124° C. at a temperature decrease rate of 80° C./min;
7) the temperature is held at 124° C. for 15 minutes, and then increased to 180° C. at a temperature increase rate of 200° C./min;
8) the temperature is held at 180° C. for 5 minutes, and then decreased to 125° C. at a temperature decrease rate of 80° C./min; and
9) the temperature is held at 125° C. for 30 minutes, and then increased to 180° C. at a temperature increase rate of 200° C./min, wherein the isothermal crystallization time at 125° C. is measured, assuming that a time of reaching 125° C. is a point of origin, 0 min.
2. The ethylene polymer according to claim 1 , wherein a difference between a melting point at a first melting peak (Tm1) and a melting point at a second melting peak (Tm2) obtained using the differential scanning calorimeter (DSC) is 0° C. or more and less than 10° C.
3. The ethylene polymer according to claim 1 , wherein a difference between a melting start temperature at a first melting peak and a melting start temperature at a second melting peak obtained using the differential scanning calorimeter (DSC) is 5.0° C. or more.
4. The ethylene polymer according to claim 1 , wherein a total content of Ti and Al is 1.0 ppm or more and 30.0 ppm or less.
5. The ethylene polymer according to claim 1 , wherein a content of chlorine is 30 ppm or less.
6. The ethylene polymer according to claim 1 , wherein a total content of hydrocarbon components respectively having 16 and 18 carbon atoms extracted with hexane is 200 ppm or less.
7. A stretched molded article, comprising the ethylene polymer according to claim 1 .
8. A microporous membrane, comprising the ethylene polymer according to claim 1 .
9. A fiber, comprising the ethylene polymer according to claim 1 .