Copolymer, method for its production, wire coating resin material and electric wire

1. A copolymer, comprising

structural units derived from ethylene,

structural units derived from tetrafluoroethylene, and

structural units derived from a third monomer,

wherein in an elution curve obtained by a temperature rising elution fractionation method with respect to the copolymer, a ratio (L/H) of a proportion (L: area %) of components with elution temperatures of from 190 to 200° C. to a proportion (H: area %) of components with elution temperatures of at least 205° C., and a proportion (M: mol %) of the structural units derived from the third monomer based on all structural units of the copolymer, satisfy a relation of the following formula (I):

log( L/H )/ M≥ 0.90  (I).

2. The copolymer according to claim 1 , wherein a proportion of the structural units derived from tetrafluoroethylene based a total of the structural units derived from ethylene and the structural units derived from tetrafluoroethylene, is from 40 to 70 mol %.

3. The copolymer according to claim 1 , wherein a proportion of the structural units derived from the third monomer based on all structural units of the copolymer is from 0.1 to 5 mol %.

4. The copolymer according to claim 1 , wherein the third monomer is a fluoroalkyl ethylene or a perfluoro(alkyl vinyl ether).

5. The copolymer according to claim 1 , which has a melting point of from 230 to 280° C.

6. The copolymer according to claim 1 , which has a melt flow rate of 1 to 50 g/10 min as measured in accordance with ASTM D3159 under conditions of a temperature of 297° C. and a load of 49N.

7. A wire coating resin material, comprising the copolymer according to claim 1 .

8. An electric wire, comprising

a core wire and

a coating layer made of the wire coating resin material according to claim 7 coated on the core wire.

9. The electric wire according to claim 8 , wherein the coating layer has a thickness of from 0.01 to 5 mm.

10. The electric wire according to claim 8 , wherein the core wire has a cross sectional area of from 0.01 to 200 mm 2 .

11. A method for producing the copolymer according to claim 1 , the method comprising

initiating polymerization by charging ethylene, tetrafluoroethylene and the third monomer into a polymerization vessel, and

subsequently supplying additional ethylene, tetrafluoroethylene and the third monomer continuously or intermittently into the polymerization vessel,

wherein a proportion (m2: mol %) of the third monomer to be additionally supplied based on a total of ethylene and tetrafluoroethylene to be additionally supplied, is differentiated from a proportion (M1: mol %) of the structural units derived from the third monomer based on all structural units of the copolymer to be formed at the initial stage of polymerization so that m2/M1 is at least 1.10.

12. The method according to claim 11 , wherein a compound having a chlorine-carbon bond is not permitted to substantially exist in the polymerization vessel.

13. The method according to claim 11 , wherein a proportion of the structural units derived from tetrafluoroethylene based on a total of the structural units derived from ethylene and the structural units derived from tetrafluoroethylene in the obtained copolymer, is from 40 to 70 mol %.

14. The method according to claim 11 , wherein a proportion of the structural units derived from the third monomer based on all structural units of the copolymer, is from 0.1 to 5 mol %.

15. The method according to claim 11 , wherein the third monomer is a fluoroalkyl ethylene or a perfluoro(alkyl vinyl ether).