Method for Producing Expanding Styrene Polymer Granules

• US 20080203597A1
• Filed: 02/15/2006
• Published: 08/28/2008
• Est. Priority Date: 02/21/2005
• Status: Active Grant

• Current Assignee: Sulzer Chemtech (UK) Ltd. (Sulzer AG)
• Original Assignee: Sulzer Chemtech (UK) Ltd. (Sulzer AG)
• Inventors: Prokopenko, Alexej Vladimirovich, Krasheninnikov, Alexandr Alexeevich, Rogov, Maxim Nikolaevich, Rahimov, Halyl Halafovich, Tarkova, Eugenia Michailova, Ginzburg, Leonid Isaakovich, Ishmijarov, Marat Hafisovich, Mjachin, Sergei Ivanovich, Mjasitsheva, Irina Vladimirovna
• Granted Patent: US 8,361,362 B2
• Time in Patent Office: Days
• US Class Current: 264/51
• CPC Class Codes: B29C 44/3446 Feeding the blowing agent
• CPC Class Codes: B29C 44/3461 Making or treating expandable particles
• CPC Class Codes: B29K 2025/00 Use of polymers of vinyl-aromatic compounds or derivatives thereof as moulding material

Abstract

A method for supplying molten polymer and expanding agent flows to a mixing area, by dispersing the expanding agent in a polymer melt by a rapid dividing mixing in a first static mixer, holding and intensively dividingly mixing the thus obtained mixture in a second static mixer, cooling the mixture, during mixing, in a third static mixer to an intermediate temperature, cooling the mixture to a granulation temperature, extruding polymer threads and subsequently quenching and granulating them. During processing, a weight ratio between the polymer melt flow G_p and the expanding agent flow G_BA ranges from 13.0 to 19.0, a temperature in the first static mixer for rapid dividing mixing is calculated according to formula (I), in the second and third static mixed according to formulas (II) and (III), respectively, wherein G_{BA max.} is the quantity of a maximum possible expanding agent flow, GB_Bct. is the quantity of the used expanding agent flow at the ratio between the melt flow index and a weight average molecular mass (M_w) ranges within of (0.8-12.0)×10⁻⁵. The method of this invention makes it possible to produce polysteren in the form of expanding granules, within a wide range of molecular masses, and a shock-resistant polysterene.

Claims

1. A method for production of expandable polystyrene beads by supplying a polymer melt flow and an expanding agent flow to a mixing zone, dispersing the expanding agent in the polymer melt under simultaneous thorough shear mixing in a first static mixer, holding a resulting mixture in a second static mixer with simultaneous thorough shear mixing, cooling the mixture in a third static mixer with simultaneous mixing to an intermediate temperature with subsequent cooling of the mixture down to a temperature required for granulation, and extruding polymer filaments on a shock cooling and a resulting granulation, the method comprising:

maintaining a weight ratio between the melt flow Gp and the expanding agent flow G_EA within a range of 13 to 19 and a temperature in the first static mixer being

$\left[200+56·<br><br>\left(1-\frac{G_{\mathrm{EAcurrent}.}}{G_{\mathrm{EA}<br><br><br><br>\max }}\right)\right]<br><br><br><br>\mathrm{°<br><br>}<br><br><br><br>C.,$

in the second static mixer being

$\left[175+70·<br><br>\left(1-\frac{G_{\mathrm{EAcurrent}.}}{G_{\mathrm{EA}<br><br><br><br>\max }}\right)\right]<br><br><br><br>\mathrm{°<br><br>}<br><br><br><br>C.,$

and in the third static mixer being

$\left[150+70·<br><br>\left(1-\frac{G_{\mathrm{EAcurrent}.}}{G_{\mathrm{EA}<br><br><br><br>\max }}\right)\right]<br><br><br><br>\mathrm{°<br><br>}<br><br><br><br>C.,$

where

GE_max is a maximum possible expanding agent flow rate, and

G_EAcurrent is a flow rate of the expanding agent.

and where a second ratio between a melt flow index (MFI) of the polymer melt and a weight-average molecular weight (M_w) is maintained within a range of (0.8 to 12.0)×

10<sup>−

5</sup>.

2. The method according to claim 1, wherein a homopolystyrene is used as styrene polymer.

3. The method according to claim 1, wherein an impact polystyrene is used as styrene polymer.

4. The method according to claim 1, wherein at least one of a pentane, an isopentane and their compounds are used as the expanding agent.