Method for the production of transparent polyamides
A process for manufacturing a transparent polyamide including a step of polycondensation of a mixture of monomers including at least one dicarboxylic acid and at least one cycloaliphatic diamine, in which the cycloaliphatic diamine includes two rings linked by an alkylene group including 1 to 6 carbon atoms, each ring being substituted by an amine group and at least one alkyl group, which may be identical or different, including 1 to 6 carbon atoms, wherein the diamine decomposes into six isomer fractions when it is subjected to analysis by gas chromatography on a nonpolar column and, when the isomer fractions are named isomer fractions I to VI in their order of elution, the mass content F I of fraction I of the cycloaliphatic diamine does not exceed 35%. A transparent polyamide capable of being obtained by the process, and to articles obtained from such a polyamide or from such a formulation.
1. A process for manufacturing a transparent polyamide comprising a step of polycondensation of a mixture of monomers comprising at least one dicarboxylic acid and at least one cycloaliphatic diamine,
in which the cycloaliphatic diamine comprises two rings linked by an alkylene group comprising 1 to 6 carbon atoms, each ring being substituted by an amine group and at least one alkyl group, which may be identical or different, comprising 1 to 6 carbon atoms,
wherein the diamine decomposes into six isomer fractions when it is subjected to analysis by gas chromatography on a nonpolar column and wherein, when said isomer fractions are named isomer fractions I to VI in their order of elution, the mass content F I of fraction I of said cycloaliphatic diamine does not exceed 33%,
wherein the dicarboxylic acid is a mixture of terephthalic acid and isophthalic acid comprising at least 50 mol % of terephthalic acid,
wherein the cycloaliphatic diamine is bis(3-methyl-4-aminocyclohexyl)methane and the polycondensation is carried out in the presence of lauryllactam or aminoundecanoic acid.
2. The process as claimed in claim 1 , in which at least one cycloaliphatic diamine is characterized by a mass content of isomer fraction F II which is greater than its mass content of isomer fraction F I .
3. The process as claimed in claim 1 , in which the at least one cycloaliphatic diamine is characterized by a difference ΔF II/I between the mass content of isomer fraction II and isomer fraction I which is greater than 0%.
4. The process as claimed in claim 1 , in which the dicarboxylic acid is a mixture of terephthalic acid and isophthalic acid comprising at least 60 mol % of terephthalic acid.
5. The process as claimed in claim 1 , in which the polycondensation is carried out in the presence of aminoundecanoic acid.
6. The process as claimed in claim 1 , in which the polycondensation is carried out in the presence of lauryllactam.
7. A transparent polyamide obtained by the process as claimed in claim 1 .
8. A formulation obtained from a transparent polyamide as claimed in claim 7 via mixing with one or more other polymers, additives, fillers and/or modifiers.
9. Articles obtained from a transparent polyamide as claimed in claim 7 .
10. The process as claimed in claim 1 , in which the dicarboxylic acid is a mixture of terephthalic acid and isophthalic acid comprising at least 75 mol % of terephthalic acid.
11. The process as claimed in claim 1 , in which the mass content F I of fraction I of said cycloaliphatic diamine does not exceed 30%.