POLYMER HAVING EXCELLENT COMPATIBILITY WITH THERMOPLASTIC RESIN

The purpose of the present invention is to provide a polymer having excellent compatibility with thermoplastic resins. The present invention is a polymer (B), which essentially contains units represented by the following formulas (1), (2) and (3), wherein the number of moles of the unit (1) is 0 to 95, the number of moles of the unit (2) is 0 to 50, and the number of moles of unit (3) is 2 to 80 when the total number of moles of the units (1), (2) and (3) is 100.in the units (1) to (3), "X" is a recurring unit having a benzene ring, in the unit (2), -CH3 is a methyl group substituted for the hydrogen atom of the benzene ring of "X", "m" is an integer of 1 to 6 indicative of the number of the methyl group, the unit (3) is a unit obtained by substituting the hydrogen atom of -CH3 in the unit (2) by a substituent "Z" derived from a carboxylic acid or anhydride thereof, "n" is an integer of 1 to 6 indicative of the number of substitutions, l+n=m, and the unit (3) is a unit in which "n" is 1, 2, 3, 4, 5, 6 or a combination thereof.