Copolymers having amide units and ether units with improved optical properties

Process for the preparation of the copolymer of claim 25, wherein said polycondensation reaction comprises two stages comprising:

• preparing in a first stage, the polyamide PA blocks by polycondensation
• of the diamine or diamines;
• of the dicarboxylic acid or acids;
• and
• if appropriate, of the other polyamide comonomer or comonomers;
• in the presence of a chain-limiting agent chosen from dicarboxylic acids;
• then
• reacting in a second stage, the polyamide PA blocks obtained are reacted with polyether PE blocks in the presence of a catalyst.

Process for the preparation of a copolymer based on amide units and based on ether units the amide units being composed predominantly of an equimolar combination of at least one diamine and of at least one dicarboxylic acid, the diamine or diamines being predominantly cycloaliphatic and the dicarboxylic acid or acids being predominantly linear aliphatic, it being possible for the amide units optionally to comprise, but to a minor extent, at least one other polyamide comonomer, the respective proportions of monomers of the ether and amide units being chosen so that:

• the said copolymer exhibits a high transparency which is such that the transmission at 560 nm through a sheet with a thickness of 2 mm is greater than 75%;
• the said copolymer is amorphous or exhibits a crystallinity such that the enthalpy of fusion during the second heating of an ISO DSC (delta Hm(2)) is at most equal to 30 J/g, the weight being with respect to the amount of amide units present or of polyamide present, this melting corresponding to that of the amide units;
• and
• the said copolymer has a glass transition temperature at least equal to 75° C., the said polymer being provided in the form of polyamide PA—polyether PE blocks, comprising the step of performing a one-stage polycondensation is carried out involving
• the diamine or diamines;
• the dicarboxylic acid or acids;
• and
• if appropriate, the other polyamide comonomer or comonomers;
• wherein said polycondensation occurs:
• in the presence of a chain-limiting agent chosen from dicarboxylic acids;
• in the presence of the PE blocks;
• and
• in the presence of a catalyst for the reaction between the PE (polyether) blocks and the PA blocks.

Transparent or translucent shaped article, selected from the group consisting of fibre, fabric, film, sheet, rob, pipe or injection-moulded component, comprising the copolymer based on amide units and based on ether units, the amide units being composed predominantly of an equimolar combination of at least one diamine and of at least one dicarboxylic acid, the diamine or diamines being predominantly cycloaliphatic and the dicarboxylic acid or acids being predominantly linear aliphatic, it being possible for the amide units optionally to comprise, but to a minor extent, at least one other polyamide comonomer, the respective proportions of monomers of the ether and amide units being chosen so that:

• the said copolymer exhibits a high transparency which is such that the transmission at 560 nm through a sheet with a thickness of 2 mm is greater than 75%;
• the said copolymer is amorphous or exhibits a crystallinity such that the enthalpy of fusion during the second heating of an ISO DSC (delta Hm(2)) is at most equal to 30 J/g, the weight being with respect to the amount of amide units present or of polyamide present, this melting corresponding to that of the amide units;
• and
• the said copolymer has a glass transition temperature at least equal to 75° C.