| 摘要 |
The present invention is a method to start-up a process to make expandable vinyl aromatic polymer pellets comprising, a) providing a pelletizer (S) containing means to introduce the molten vinyl aromatic polymer comprising the expandable agent and optionally additives, a die plate having a plurality of holes of small diameter, typically in the range 0.8 to 1.6 mm and cutting means to make pellets, b) providing a pelletizer (L) containing means to introduce the molten vinyl aromatic polymer comprising the expandable agent and optionally additives, a die plate having a plurality of holes of large diameter, typically in the range 3 to 5 mm and cutting means to make pellets, c) sending the expandable vinyl aromatic polymer pellets comprising an expandable agent and optionally additives to the pelletizer (L) until the polymer flow rate is in the operating range of the pelletizer (S) and provided the proportion of expandable agent and optional additives are in the specifications, d) switching the molten vinyl aromatic polymer stream comprising the expandable agent and optionally additives to the pelletizer (S) and operating said pelletizer (S) at conditions effective to produce expandable vinyl aromatic polymer pellets, e) recovering from pelletizer (S) the expandable vinyl aromatic polymer pellets, f) recovering the pellets produced at step c) for optional subsequent recycling in the molten state at step d). In another embodiment while the pelletizer (S) is in production and troubles happen in the introduction of the expanding agent and/or the optional additives or in any equipment or even an equipment needs maintenance the production is switched from the pelletizer (S) to one or more pelletizers (L). When the troubles are over, the production is switched from the pelletizer (L) to the pelletizer (S). In an embodiment while the pelletizer (S) is in production the die plate of the pelletizer (L) having a plurality of holes of large diameter is removed and replaced by a die plate having a plurality of holes of small diameter to convert said pelletizer (L) into a pelletizer (S) capable to produce expandable vinyl aromatic polymer pellets. By way of example said established pelletizer (S) is used during maintenance of the other pelletizer (S). |
