During the production of PET preforms, the molecule acetaldehyde (AA) is formed as a by-product of PET. AA can also be found in nature, e.g. in citrus fruits. Because if its intense taste an excessively high AA content in PET preforms is undesirable. In addition to the recipe, the main influencing factors for the formation of AA when processing PET are the residence time and the processing temperature. Since the residence time in the laminar PET melt flow is uneven, local AA concentrations occur in individual cavities of the mould. This means that in one injection cycle, within a large number of high quality preforms, some with too high AA concentration may occur. This can be counteracted conservatively by using AA blockers. The problem is that AA blockers may also migrate and therefore, corresponding legal limits must be observed. Moreover, AA blockers represent an additional cost factor.
By using the Promix PET mixing nozzle specially developed for this application, local AA concentrations are evenly distributed in the melt flow. This prevents individual outliers. Since the peaks are reduced by an average of 20-30 %, all cavities are then below the permissible AA limit. If AA blockers are used, their effect is optimised thanks to the better distribution in the melt. This leads to significant savings in AA blockers. Not infrequently, it is even possible to eliminate AA blockers entirely, which permanently lowers production costs.
The Promix PET mixing nozzle is also claimed to make an important contribution to the circular economy. On average, new PET bottles contain at least 30-40% recyclate, and the trend is rising. The Promix PET mixing nozzle supports a higher recyclate content, as it helps to better homogenise the lower-viscosity bottle flakes in the melt stream. In addition, it ensures good colour distribution in coloured preforms.
The Promix PET mixing nozzle was specially designed for the high pressures and fast injection times in PET preform production and is retrofittable.