Method for the production of expandable plastics granulate
AssigneeSulzer Chemtech AG
InventorAndreas Walder
Life of this patent
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Abstract
Apparatus and method for the production of expandable plastics granulate (C). A plastics melt (A′) is impregnated by a fluid blowing agent (B), which is, at an elevated pressure within a predetermined pressure range, only partly soluble in the melt. The method comprises the following steps: 1. dispersion of the blowing agent in the melt, 2. retaining of the mixture within a predetermined pressure range for a predetermined retention time, 3. cooling of the melt impregnated by the blowing agent to a temperature which is several degrees Celsius above the solidification temperature of the melt, and 4. granulating the cooled mixture.
Claims4
In a method for producing expandable plastic granulate from a plastic material and a fluid blowing agent that is only partially soluble in the plastic material when the plastic material is at an elevated temperature by
- heating the plastic material to the elevated temperature to form a plastic melt;
- dispersing the blowing agent in the melt to form a mixture;
- retaining the mixture for a predetermined time at the elevated temperature and pressure for a predetermined time interval;
- and
- thereafter cooling and granulating the mixture,
- the improvement comprising:
- providing a first static mixer in which the dispersing step is carried out and which subjects the mixture to intensive shearing;
- and
- providing a second static mixer in which the retaining step is carried out and which subjects the mixture to less intensive shearing than in the first static mixer.
A method for producing expandable plastic granulate from a plastic material and a fluid blowing agent comprising
- melting the plastic material at an elevated temperature to form a melt and subjecting the melt to an elevated pressure;
- providing first and second, serially arranged static mixers, the first static mixer having a relatively smaller cross-sectional flow-through area and the second mixer has a relatively larger cross-sectional flow-through area;
- injecting the blowing agent into the melt to form a flowable mixture;
- flowing the mixture serially through the first and second static mixers wherein the smaller cross-sectional area of the first static mixer subjects the mixture to relatively high intensity shearing as the mixture flows through the first static mixer and the larger cross-sectional flow-through area of the second static mixer subjects the mixture to relatively less intense shearing as the mixture flows through the second static mixer;
- and
- thereafter cooling the mixture and forming expandable granulate therefrom.
Dependencies are inferred from the claim text.