Extrusion expansion of low molecular weight polyalkylene terephthalate for production of expanded beads
AssigneeArmacell Enterprise GmbH
InventorsKarl Paetz-Lauter, Jie Li, Mika Meller
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Abstract
An extrusion expansion of low molecular weight polyalkylene terephthalates having an IV of below 1.0 dl/g to produce gas-charged beads is disclosed. The process includes an extrusion expanding of the resins and an underwater pelletizing of the melt threads. The obtained beads show a composite structure and are characterized by an IV of 0.69 dl/g or more and a melt viscosity η0 of higher than 300 Pa·s.
Claims10
Expanded beads of a polyalkylene terephthalate resin, wherein the expanded beads comprise a cellular core encapsulated by a compact skin, wherein the cellular core comprises a fine-cell center and a microcellular layer,
- wherein the compact skin has a thickness between 30 μm and less than 120 μm;
- wherein the microcellular layer is adjacent to the compact skin and has a thickness not higher than 100 μm and a cell size below 15 μm;
- wherein the fine-cell center has a cell size below 400 μm, and
- wherein the expanded beads have an intrinsic viscosity of at least 0.69 dl/g according to ASTM D4603-03, a melt viscocity η0 of more than 300 Pa·s according to ASTM D4440 at 280° C. and a density 400 kg/m3 according to DIN ISO 1183.
Dependencies are inferred from the claim text.