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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
First Claim
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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 GEA within a range of 13 to 19 and a temperature in the first static mixer being [ 200 + 56 ·

    ( 1 - G EAcurrent . G EA



    max
    )
    ]




    °





    C .
    ,
    in the second static mixer being [ 175 + 70 ·

    ( 1 - G EAcurrent . G EA



    max
    )
    ]




    °





    C .
    ,
    and in the third static mixer being [ 150 + 70 ·

    ( 1 - G EAcurrent . G EA



    max
    )
    ]




    °





    C .
    ,
    whereGEmax is a maximum possible expanding agent flow rate, andGEAcurrent 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 (Mw) is maintained within a range of (0.8 to 12.0)×

    10

    5
    .

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