Thermoplastic copolyimides

A semiaromatic semicrystalline thermoplastic copolyimide obtained by polymerization of at least:

• (a) an aromatic compound comprising two anhydride functions and/or carboxylic acid and/or ester derivatives thereof;
• (b) a diamine of formula (I) NH2—R—NH2 selected from the group consisting of:
• 1,4-diaminobutane, 1,5-diaminopentane, 2-methyl-1,5-diaminopentane, hexamethylenediamine, 3-methylhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,2,4- and 2,4,4-trimethyl-hexamethylenediamine, 1,7-diaminoheptane, 1,8-diaminooctane;
• and
• (c) a diamine of formula (II) NH2—R′—NH2 in which R′ is a saturated or unsaturated, linear or branched, divalent aliphatic hydrocarbon-based radical, optionally comprising heteroatoms, wherein the two amine functions are separated by a number Y of carbon atoms, Y is between 10 and 20, and the radical R′ comprises not more than 20 carbon atoms;
• wherein the copolyimide has at least two melting points Tf, and the melting points are between 50° C. and 330° C., measured by differential scanning calorimetry and heating the copolyimide from 20° C. at a rate of 10° C./minute.

A process for manufacturing a copolyimide, comprising copolymerizing at least:

• (a) an aromatic compound comprising two anhydride functions and/or carboxylic acid and/or ester derivatives thereof;
• (b) a diamine of formula (I) NH2—R—NH2 selected from the group consisting of:
• 1,4-diaminobutane, 1,5-diaminopentane, 2-methyl-1,5-diaminopentane, hexamethylenediamine, 3-methylhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,2,4- and 2,4,4-trimethyl-hexamethylenediamine, 1,7-diaminoheptane, 1,8-diaminooctane;
• and
• (c) a diamine of formula (II) NH2—R′—NH2 in which R′ is a saturated and/or unsaturated, linear or branched, divalent aliphatic hydrocarbon-based radical, optionally comprising heteroatoms, the two amine functions being separated by a number Y of carbon atoms, Y being between 10 and 20, the radical R′ comprising not more than 20 carbon atoms;
• wherein the copolyimide has at least two melting points Tf, and the melting points are between 50° C. and 330° C., measured by differential scanning calorimetry and heating the copolyimide from 20° C. at a rate of 10° C./minute.