Ultra-high molecular weight ethylene-based copolymer powder, and molded article using ultra-high molecular weight ethylene-based copolymer powder

1. An ultra-high molecular weight ethylene-based copolymer powder comprising:

an ethylene unit and an α-olefin unit having 3 or more and 8 or less carbon atoms as structural units,

wherein the ultra-high molecular weight ethylene-based copolymer powder has a viscosity-average molecular weight of 100,000 or more and 10,000,000 or less,

a content of the α-olefin unit is 0.01 mol % or more and 0.10 mol % or less based on a total amount of the ethylene unit and the α-olefin unit, and

in measurement with a differential scanning calorimeter under following conditions, an isothermal crystallization time is determined as a time from reaching 126° C. of Step A3 as a starting point (0 min) to giving an exothermic peak top due to crystallization and the isothermal crystallization time is 5 minutes or more (Conditions for measurement of isothermal crystallization time);

Step A1: holding at 50° C. for 1 minute and then an increase up to 180° C. at a temperature rise rate of 10° C./min,

Step A2: holding at 180° C. for 30 minutes and then a decrease down to 126° C. at a temperature drop rate of 80° C./min, and

Step A3: holding at 126° C.

2. The ultra-high molecular weight ethylene-based copolymer powder according to claim 1 , wherein in measurement with a differential scanning calorimeter under following conditions, a heat of fusion per unit mass (ΔH2) in a temperature rising process of Step B3 is 230 J/g or less (Conditions for measuring heat of fusion per unit mass (ΔH2));

Step B1: holding at 50° C. for 1 minute and then an increase up to 180° C. at a temperature rise rate of 10° C./min,

Step B2: holding at 180° C. for 5 minutes and then a decrease down to 50° C. at a temperature drop rate of 10° C./min, and

Step B3: holding at 50° C. for 5 minutes and then an increase up to 180° C. at a temperature rise rate of 10° C./min.

3. The ultra-high molecular weight ethylene-based copolymer powder according to claim 1 , wherein a content of titanium element measured with an inductively coupled plasma mass spectrometer (ICP/MS) is 6 ppm or less.

4. The ultra-high molecular weight ethylene-based copolymer powder according to claim 1 , wherein the isothermal crystallization time is 8 minutes or more.

5. The ultra-high molecular weight ethylene-based copolymer powder according to claim 1 , wherein the ultra-high molecular weight ethylene-based copolymer powder has a tap density of 0.51 g/cm 3 or more and 0.64 g/cm 3 or less, and a bulk density of 0.40 g/cm 3 or more and 0.60 g/cm 3 or less.

6. The ultra-high molecular weight ethylene-based copolymer powder according to claim 5 , wherein a ratio of the tap density to the bulk density is 1.10 or more and 1.50 or less.

7. The ultra-high molecular weight ethylene-based copolymer powder according to claim 1 , wherein the ultra-high molecular weight ethylene-based copolymer powder has an average particle diameter of 50 μm or more and 200 μm or less.

8. A molded article of the ultra-high molecular weight ethylene-based copolymer powder according to claim 1 .

9. The molded article according to claim 8 , wherein the molded article is a separator membrane for a secondary battery or fiber prepared by wet extrusion.

10. The molded article according to claim 9 , wherein the secondary battery is a lithium ion secondary battery or a lead storage battery.

11. The molded article according to claim 9 , wherein a product using the fiber is rope, net, bulletproof clothing, a protective garment, protective gloves, a fiber reinforced concrete product, or a helmet.

12. The molded article according to claim 8 , wherein the molded article is used in a lining application, a bearing, a gear, a roller guide rail, a bone substitute, a bone conductive material, or an osteoinduction material.