POLYESTER COMPOSITIONS
The invention relates to compositions based on polyethylene terephthalate and polybutylene terephthalate with optimized crystallization behavior and consequently with optimized processing behavior in the injection molding process, and also to products to be produced therefrom, in particular with optimized crystallinity.
1 . A composition comprising PBT and PET in a ratio by weight of from 5:1 to 02:1, characterized in that the PET has a sodium content and/or potassium content of from 1 to 10 000 ppm.
2 . The composition as claimed in claim 1 , comprising
a) PBT and
b) PET, preferably PET recyclate, with a sodium content and/or potassium content of from 1 to 100 ppm, obtainable via use of NaOH and/or KOH in a PET washing process,
where the PBT: PET ratio by weight is in the range from 5:1 to 0.2:1.
3 . The composition as claimed in claim 1 or 2 , characterized in that component b) is obtained via use of NaOH and/or KOH in a washing process in accordance with the following steps:
i) washing of the PET, preferably PET flakes which are obtained via shredding of used PET bottles, with aqueous solution of alkali metal hydroxide, preferably aqueous solution of sodium hydroxide and/or aqueous solution of potassium hydroxide, particularly preferably aqueous solution of sodium hydroxide,
ii) melting and mixing of the PET in a compounder, preferably in a compounder with a plurality of screws, optionally application of vacuum (devolatilization) with or without stripping for the removal of volatile contaminants, in particular of acetaldehyde and oligomers, then discharge and solidification of the melt, and pelletization,
and also optionally thereafter preferably a solid-phase postcondensation process in vacuo with or without passage of an inert gas for the removal of residual contaminants and/or viscosity increase, and also optionally a drying step prior to the melting process and/or a crystallization step between pelletization and solid-phase postcondensation.
4 . The composition as claimed in any of claims 1 to 3 , characterized in that it comprises a proportion by weight of PBT plus PET of from 40 to 99.99% by weight (terminal values included).
5 . The composition as claimed in any of claims 1 to 4 , characterized in that from 0.01 to 60 parts by weight of additives are also present, in addition to the components mentioned.
6 . The composition as claimed in claims 1 to 5 , characterized in that the sum of all of the parts by weight of PBT plus PET plus additives corresponds to 100% of the entire composition.
7 . A process for the optimization of the crystallization behavior of polyester molding compositions or of the crystallinity of the products to be produced therefrom, characterized in that a composition as claimed in any of claims 1 to 6 is used.
8 . The process as claimed in claim 7 , characterized in that this uses injection molding.
9 . The use of compositions as claimed in any of claims 1 to 6 for the optimization of the crystallization behavior of polyester molding compositions and of the crystallinity of the products to be produced therefrom.
10 . The use as claimed in claim 9 , characterized in that this takes place in the injection molding process.
11 . A product obtainable via injection molding of compositions as claimed in any of claims 1 to 6 .