The present invention I relates to a method for the preparation of a
polyester block
copolymer (P1) characterized in that in the method for the preparation of 100% by weight of the
polyester block
copolymer (P1) by allowing to react A% by weight of a crystalline aromatic
polyester with B% by weight of lactones (A+B=100), (B+0.5)% by weight of lactones are added into A% by weight of a crystalline aromatic polyester, and not less than 0.5% by weight of unreacted lactones are remained with respect to 100% by weight of the polyester block
copolymer (P1) after reaction. The present invention II relates to a method for the preparation of a polyester block copolymer (P'1) having a high molecular weight characterized in that the polyester block copolymer (P1) is allowed to further react in a
solid phase. The present invention III relates to a polyester block
copolymer composition (R) obtained by thermally-
processing a polyester block
copolymer composition (Q) obtained by melt-mixing 100 parts by weight of a polyester block copolymer (P) with 0.1-5 parts by weight of an
epoxy compound (C) having one or more
epoxy groups under an
inert gas
atmosphere and not less than 120° C. in a
solid phase, and further, at a temperature lower than a
melting point of the polyester block
copolymer composition (R). The present invention IV relates to a polyester block copolymer composition which comprises thermally-kneading 0.5-5.0 parts by weight of a mono or more functional
epoxy compound (C) and 0.01-3.0 parts by weight of a complex-formable agent for a
metal (G) such as an
oxalic acid derivative and a
salicylic acid derivative or a
hydrazide derivative with 100 parts by weight of a polyester block copolymer (P1) obtained by a reaction of a crystalline aromatic polyester (A1) with lactones (B). The present invention V relates to a polyester block copolymer composition which comprises, in obtaining the polyester block copolymer composition by allowing to react the crystalline aromatic polyester (A1) with lactones (B), adding and thermally-kneading 0.5-5.0 parts by weight of an epoxy compound (C) having one or more pieces of epoxy groups (including at least 0.2 part by weight of two or more functional epoxy compound) and, optionally, 0-2.0 parts by weight of a
carbodiimide compound (E) to 100 parts by weight of a polyester block copolymer (P3) obtained by allowing to react 0.1-100% by mol of at least one of a multifunctional compound (D) having at least three pieces of at least one kind of
carboxylic group (i), hydroxyl group (ii), and / or an ester-formable group therefrom (iii) with 100% by mol of a crystalline aromatic polyester (A1). The present invention VI relates to a polyester block copolymer composition which comprises, in obtaining said polyester block copolymer composition by allowing to react the crystalline aromatic polyester (A1) with lactones (B), adding and thermally-kneading 0.1-5.0 parts by weight of an epoxy compound (C) having one or more pieces of epoxy groups and 0-2.0 parts by weight of a
carbodiimide compound (E) to 100 parts by weight of a polyester block copolymer (P3) obtained by allowing to react 0.1-200% by mol of at least one of an aliphatic or aromatic multifunctional compound (D) having at least three pieces of
carboxylic group hydroxyl group (ii), and / or an ester-formable group therefrom (iii) with 100% by mol of a crystalline aromatic polyester (A1). The present invention VII relates to a polyester block copolymer composition (R) which comprises, in obtaining the polyester block copolymer composition by allowing to react the crystalline aromatic polyester (A1) with lactones (B), heating a polyester block copolymer composition (Q) at a
solid phase, and the composition (Q) is obtained by adding and thermally-kneading 0.1-5.0 parts by weight of at least one kind of an epoxy compound (C) having one or more pieces of epoxy groups to 100 parts by weight of a polyester block copolymer (P) obtained by allowing to react 0.1-200% by mol of at least one of a multifunctional compound (D)