EP0342750A1

Polyethylene composition, objects made therefrom and process for the manufacture of foamed objects.

Abstract

The invention relates to polyethylene compositions comprising 20-98 wt % branched polyethylene a) with a density of between 915 and 940 kg/m³ and a melt flow index of between 0.05 and 40 dg/minute, pre­pared by a high pressure radical process, and 2-80 wt % substantially linear polyethylene b) with a density of between 850 and 915 kg/m³, a melt flow index of between 0.05 and 25 dg/minute and a DSC crystalli­nity of 23¤C of at least 10 %, prepared with the aid of the transition metal catalyst, the difference between the highest crystallization temperature of branched polyethylene a) and the highest DSC crystalli­zation temperature of linear polyethylene b) being at most 10¤C and the mixture having a modulus of elasticity of at most 280 N/mm² and objects made therefrom. These polyethylene compositions, when pro­cessed to foamed objects, have a high resistance to high temperatures as well as a high flexibility.

EP0342750A1, drawing sheet 1
Sheet 1 of 17

Term

Term ended

Projected expiry passed 16 May 2009, 17.4 years ago.

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9 claims: 7 independent, 2 dependent

  1. 1
    Polyethylene composition comprising 20-98 wt % branched polyethy­lene a) with a density of between 915 and 940 kg/m³ and a melt flow index of between 0.05 and 40 dg/minute, prepared by a high pressure radical process, and 2-80 wt % substantially linear polyethylene b) with a density of between 850 and 915 kg/m³, a melt flow index of between 0.05 and 25 dg/minute and a DSC crystallinity at 23¤C of at least 10 %, prepared with the aid of a transition metal catalyst, the difference between the highest crystallization temperature of branched polyethylene a) and the highest DSC crystallization temperature of linear polyethylene b) being at most 10¤C and the mixture having a modulus of elasticity of at most 280 N/mm². 1. Process for the manufacture of a polyethylene composition comprising mixing 20-98 wt % branched polyethylene a) with a den­sity of between 915 and 940 kg/m³ and a melt flow index of between 0.05 and 40 dg/minute, prepared by a high pressure radical pro­cess, and 2-80 wt % substantially linear polyethylene b) with a density of between 850 and 915 kg/m³, a melt flow index of between 0.05 and 25 dg/minute and a DSC crystallinity at 23¤C of at least 10 %, prepared with the aid of a transition metal catalyst, the difference between the highest crystallization temperature of branched polyethylene a) and the highest DSC crystallization tem­perature of linear polyethylene b) being at most 10¤C and the mix­ture having a modulus of elasticity of at most 280 N/mm².
  2. 3
    Polyethylene composition according to any one of Claims 1-2, characterized in that the melt flow index of polyethylene a) is between 0.1 and 30 dg/minute and the melt flow index of polyethy­lene b) is between 0.1 and 20 dg/minute. 3. Process according to any one of Claims 1-2, characterized in that the melt flow index of polyethylene a) is between 0.1 and 30 dg/minute and the melt flow index of polyethylene b) is between 0.1 and 20 dg/minute.
  3. 4
    Polyethylene composition according to any one of Claims 1-3, characterized in that the composition comprises 30-90 wt % polyethylene a) and 10-70 wt % polyethylene b). 4. Process according to any one of Claims 1-3, characterized in that the composition comprises 30-90 wt % polyethylene a) and 10-70 wt % polyethylene b).
  4. 5
    Polyethylene composition according to any one of Claims 1-4, characterized in that the DSC crystallization curve of the polyethylene composition exhibits at most one crystallization peak between 125 and 95¤C. 5. Process according to any one of Claims 1-4, characterized in that the DSC crystallization curve of the polyethylene composition exhibits at most one crystallization peak between 125 and 95¤C.
  5. 6
    Process for the manufacture of foamed objects by mixing a polyethylene composition with at least one or more foaming agents at increased pressure and temperature and passing the composition via an extruder through an extrusion opening into a zone with a lower pressure and temperature, characterized in that the polyethylene composition is a composition according to any one of Claims 1-5. 6. Process for the manufacture of foamed objects by mixing a polyethylene composition with at least one or more foaming agents at increased pressure and temperature and passing the composition via an extruder through an extrusion opening into a zone with a lower pressure and temperature, characterized in that the polyethylene composition is a composition prepared according to any one of Claims 1-5.
  6. 8
    Process according to any one of Claims 6-7, characterized in that the polyethylene composition is in addition mixed with one or more crosslinking agents. 8. Process according to any one of Claims 6-7, characterized in that the polyethylene composition is in addition mixed with one or more crosslinking agents.
  7. 9
    Process according to any one of Claims 6-8, characterized in that the polyethylene composition is in addition mixed with one or more lubricants. 9. Process according to any one of Claims 6-8, characterized in that the polyethylene composition is in addition mixed with one or more lubricants.