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US 2026/0275065 A1Published application
Method for producing polycarbonate beads
AssigneeCovestro Deutschland AG
InventorsAnna Bronova, Tim Hungerland, Marius Nolte, Andreas Klein, Ulrich Grosser, Birgit Mannel, Daniel Raps, Nick Weingart, Volker Altstädt
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Abstract
The invention describes a method for producing polycarbonate beads using a chain extender. The polycarbonate beads have a low bulk density and are suitable for the production of moulded parts with good surface properties and good mechanical properties.
Claims15
1:
- A process for producing foamed polycarbonate beads, comprising the following steps:
- a) providing an aromatic polycarbonate-based composition, where the aromatic polycarbonate, based on the total weight of the aromatic polycarbonate, has a content of OH end groups of at least 350 ppm, determined by 1H NMR spectroscopy with dichloromethane as solvent at room temperature,
- b) mixing the aromatic polycarbonate-based composition with a chain extender suitable for OH groups in such a molar ratio that 0.64-1.10 mol of the reactive group of the chain extender is used per 1 mol of OH end groups of the polycarbonate,
- c) providing the mixture in a plastified state,
- d) mixing a physical blowing agent into the melt,
- e) particle foam extrusion of the plastified mixture at a temperature T of T1=(Tg+110° C.) to T2=(Tg+170° C.), where Tg is the glass transition temperature of the aromatic polycarbonate-based composition, and
- f) pelletizing the blowing agent-containing melt.
4 more elements
2:
- The process as claimed in claim 1, wherein carbon dioxide is used as the blowing agent.
3:
- The process as claimed in claim 1, wherein the process is performed as a continuous operation.
4:
- The process as claimed in claim 1, wherein the aromatic polycarbonate-based composition from step a) has a melt volume flow rate MVR of up to 12 cm3/(10 min), determined in accordance with ISO 1133:2012-3 (test temperature 300° C., mass 1.2 kg).
5:
- The process as claimed in claim 1, wherein the pelletization is a pelletization in liquid medium, by hot chopping or an under-air pelletization.
6:
- The process as claimed in claim 1, wherein the pelletization is an unpressurized underwater pelletization.
7:
- The process as claimed in claim 1, wherein the chain extender used is one or more epoxy-functionalized compounds.
8:
- The process as claimed in claim 1, wherein 0.1-2.3% by weight of physical blowing agent is added in step d, where the stated amount is based on the total weight of aromatic polycarbonate-based composition and chain extender.
9:
- The process as claimed in claim 1, wherein the aromatic polycarbonate in the composition from step a), based on the total weight of the aromatic polycarbonate, has a content of OH end groups of 350 to 600 ppm, determined by 1H NMR spectroscopy with dichloromethane as solvent at room temperature.
10:
- The process as claimed in claim 1, wherein the aromatic polycarbonate in the composition from step a), based on the total weight of the aromatic polycarbonate, has a content of OH end groups of at least 380 ppm, determined by 1H NMR spectroscopy with dichloromethane as solvent at room temperature.
11:
- The process as claimed in claim 1, wherein step b) and step d) overlap in time.
12:
- The process as claimed in claim 1, wherein steps a) to f) take place in the sequence stated.
13:
- The process as claimed in claim 1, wherein the chain extender used is an epoxy-functionalized chain extender with an epoxy equivalent weight of 285 to 485 g/mol.
14:
- Polycarbonate beads produced by the process as claimed in claim 1.
15:
- A process for producing molded articles from the polycarbonate beads as claimed in claim 14, wherein the crack gap method or the pressure filling method is utilized.