Conjugated diene-based polymer, method for producing the same, and composition including the same

1. A method for producing a conjugated diene-based polymer, comprising:

a step of polymerizing a monomer including at least one conjugated diene monomer by use of an organolithium compound as an initiator, and

a step of adding a compound (II) represented by the following formula (II) and a compound (III) represented by the following formula (III):

wherein R 3 and R 4 each independently represent a hydrocarbon group having 1 to 20 carbon atoms; and

wherein R 5 and R 6 each independently represent a hydrocarbon group having 1 to 20 carbon atoms;

wherein when a weight ratio (%) of the compound (II) to a total of the compound (II) and the compound (III) is defined as (A) as shown by formula 1 and a molar ratio of the compound (II) and the compound (III) to lithium of the polymerization initiator is defined as (B) as shown by formula 2, amounts of the polymerization initiator, the compound (II) and/or the compound (III) to be added are regulated so that (A)×(B) is 0.5 or less as shown by formula 3:

( A )=(Compound (II)/(Compound (II)+Compound (III)))×100  Formula 1:

( B )=([Compound (II)]+[Compound (III)])/[Li]  Formula 2:

( A )×( B )≤0.5  Formula 3.

2. The method according to claim 1 , wherein the conjugated diene-based polymer comprises at least one conjugated diene monomer, wherein 40% or more of an end thereof is an end having an amino group and an amide group, and an indicator b* value of yellowness, as measured with a colorimetric color difference meter, is 15 or less,

wherein the end having the amino group and the amide group comprises an end having a structure represented by the following formula (I):

wherein P represents a conjugated diene-based polymer comprising at least one conjugated diene monomer, and R 1 and R 2 each independently represent a hydrocarbon group having 1 to 20 carbon atoms.

3. The method according to claim 2 , wherein the end having the amino group and the amide group comprises an end having a structure represented by the following formula (I) and an end having a structure represented by the following formula (IV), and the indicator b* value of yellowness, as measured with a colorimetric color difference meter, is 15 or less:

wherein P represents a conjugated diene-based polymer comprising at least one conjugated diene monomer, and R 1 and R 2 each independently represent a hydrocarbon group having 1 to 20 carbon atoms; and

wherein P represents a conjugated diene-based polymer comprising at least one conjugated diene monomer, and R 1 and R 2 each independently represent a hydrocarbon group having 1 to 20 carbon atoms.

4. The method according to claim 2 , wherein the b* value is 9 or less.

5. A polymer composition comprising:

(a) 1 to 99 parts by weight of a conjugated diene-based polymer obtained by the method according to claim 1 , and

(b) 99 to 1 part by weight of a thermoplastic polymer and/or a rubber polymer.

6. The method according to claim 1 , wherein R 3 and R 4 each independently represent a hydrocarbon group having 1 to 8 carbon atoms.

7. The method according to claim 1 , wherein R 5 and R 6 each independently represent a hydrocarbon group having 1 to 8 carbon atoms.

8. The method according to claim 1 , wherein R 3 and R 4 each independently represent a group selected from the group consisting of an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group and an aryl group.

9. The method according to claim 1 , wherein R 5 and R 6 each independently represent a group selected from the group consisting of an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group and an aryl group.

10. The method according to claim 1 , wherein the organolithium compound is selected from the group consisting of ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene lithium, butadienyl dilithium and isoprenyl dilithium.

11. The method according to claim 1 , wherein the polymerizing step is performed at a temperature from −10 to 150° C.

12. The method according to claim 1 , wherein the compound (II) is selected from the group consisting of 1,3-diethyl-2-imidazolinone, 1,3-dimethyl-2-imidazolinone, 1,3-dipropyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 1-methyl-3-propyl-2-imidazolinone, 1-methyl-3-butyl-2-imidazolinone and 1,3-dihydro-1,3-dimethyl-2H-imidazol-2-one.

13. The method according to claim 1 , wherein the compound (III) is selected from the group consisting of 1,3-diethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-propyl-2-imidazolidinone and 1-methyl-3-butyl-2-imidazolidinone.