Urethane polymer and oil composition containing same

A urethane polymer having a structure represented by general formula (1) below:

• wherein R1 and R2 each independently denote an alkylene group having 5 to 40 carbon atoms, Z1 and Z2 each denote an oxyalkylene group represented by general formula (2) or (3) below, R3 denotes a diisocyanate residue, X1 denotes a hydrogen atom or a group represented by general formula (4) below, X2 denotes a hydrogen atom or a group represented by general formula (5) below, and n denotes a number from 1 to 20, provided that n is 1 if X1 and X2 are each a hydrogen atom;
• wherein a1, b1 and c1 denote a ratio a1:b1:c1=1-0.6:0-0.4:0-0.4 (a sum of a1, b1 and c1 is 1), and p denotes a number from 4 to 60 and wherein arrangement of structural units may be block-like or random;
• wherein a2, b2 and c2 denote a ratio a2:b2:c2=1-0.6:0-0.4:0-0.4 (a sum of a2, b2 and c2 is 1), and q denotes a number from 4 to 60 and wherein arrangement of structural units may be block-like or random;
• wherein a3, b3 and c3 denote a ratio a3:b3:c3=1-0.6:0-0.4:0-0.4 (a sum of a3, b3 and c3 is 1), and r denotes a number from 4 to 60 and wherein arrangement of structural units may be block-like or random;
• wherein a4, b4 and c4 denote a ratio a4:b4:c4=1-0.6:0-0.4:0-0.4 (a sum of a4, b4 and c4 is 1), and s denotes a number from 4 to 60 and wherein arrangement of structural units may be block-like or random.