Styrene-Modified Linear Low-Density Polythylene-Based Resin Beads, Styrene-Modified Linear Low-Density Polyethylene-Based Expandable Resin Beads, Production Method Therefor, Pre-Expanded Beads and Expanded Molded Article

Abstract

A method for producing styrene-modified linear low-density polyethylene-based resin beads, which includes the steps of: dispersing 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin beads which are polymerized using a metallocene compound as a catalyst and contain an inorganic nucleating agent, 50 to 800 parts by weight of a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer into an aqueous suspension containing a dispersant; impregnating the polyethylene-based resin beads with the styrene-based monomer under heating the resulting dispersion at such a temperature that the styrene-based monomer does not substantially polymerize; and performing polymerization of the styrene-based monomer at a temperature of (T+10) to (T+35)° C. where T° C. is a crystallization peak temperature of the polyethylene-based resin beads.

1 . A method for producing styrene-modified linear low-density polyethylene-based resin beads, comprising the steps of: 
 dispersing 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin beads which are polymerized using a metallocene compound as a catalyst and contain an inorganic nucleating agent, 50 to 800 parts by weight of a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer into an aqueous suspension containing a dispersant;    impregnating the polyethylene-based resin beads with the styrene-based monomer under heating the resulting dispersion at such a temperature that the styrene-based monomer does not substantially polymerize; and    performing polymerization of the styrene-based monomer at a temperature of (T+10) to (T+35)° C. (where T° C. is a crystallization peak temperature of the polyethylene-based resin beads).    
   
   
       2 . A method for producing styrene-modified linear low-density polyethylene-based resin beads according to  claim 1 , wherein the styrene-based monomer is used in an amount of 50 to 300 parts by weight.  
   
   
       3 . A method for producing styrene-modified linear low-density polyethylene-based resin beads according to  claim 1 , wherein the low-density polyethylene-based resin beads have a molecular weight distribution (Mw/Mn) of 1.5 to 3.5 measured by GPC and a density of 0.910 to 0.925 g/cm 3 .  
   
   
       4 . A method for producing styrene-modified linear low-density polyethylene-based resin beads, comprising the steps of: 
 dispersing 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin beads which are polymerized using a metallocene compound as a catalyst and contain an inorganic nucleating agent, 30 to 300 parts by weight of a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer into an aqueous suspension containing a dispersant;    impregnating the polyethylene-based resin beads with the styrene-based monomer under heating the resulting dispersion at such a temperature that the styrene-based monomer does not substantially polymerize;    performing first polymerization of the styrene-based monomer at a temperature of (T+10) to (T+35)° C. (where T° C. is a crystallization peak temperature of the polyethylene-based resin beads); and    subsequent to the first polymerization, adding a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer and adjusting the temperature of the resulting dispersion to (T+10) to (T+35)° C. (where T° C. is a crystallization peak temperature of the polyethylene-based resin beads), so that impregnation of the low-density polyethylene-based resin beads with the styrene-based monomer and second polymerization take place, wherein the total amount of the styrene-based monomers used in the first and second polymerization is 50 to 800 parts by weight relative to 100 parts by weight of the polyethylene-based resin beads.    
   
   
       5 . A method for producing styrene-modified linear low-density polyethylene-based resin beads according to  claim 4 , wherein the low-density polyethylene-based resin beads have a molecular weight distribution (Mw/Mn) of 1.5 to 3.5 measured by GPC and a density of 0.910 to 0.925 g/cm 3 .  
   
   
       6 . A method for producing styrene-modified linear low-density polyethylene-based expandable resin beads, comprising the steps of: 
 dispersing 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin beads which are polymerized using a metallocene compound as a catalyst and contain an inorganic nucleating agent, 50 to 800 parts by weight of a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer into an aqueous suspension containing a dispersant;    impregnating the polyethylene-based resin beads with the styrene-based monomer under heating the resulting dispersion at such a temperature that the styrene-based monomer does not substantially polymerize;    performing polymerization of the styrene-based monomer at a temperature of (T+10) to (T+35)° C. (where T° C. is a crystallization peak temperature of the polyethylene-based resin beads); and    impregnating the resin beads during or after the polymerization with a volatile blowing agent.    
   
   
       7 . A method for producing styrene-modified linear low-density polyethylene-based expandable resin beads according to  claim 6 , wherein the styrene-based monomer is used in an amount of 50 to 300 parts by weight.  
   
   
       8 . A method for producing styrene-modified linear low-density polyethylene-based expandable resin beads according to  claim 6 , wherein the low-density polyethylene-based resin beads have a molecular weight distribution (Mw/Mn) of 1.5 to 3.5 measured by GPC and a density of 0.910 to 0.925 g/cm 3 .  
   
   
       9 . A method for producing styrene-modified linear low-density polyethylene-based expandable resin beads, comprising the steps of: 
 dispersing 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin beads which are polymerized using a metallocene compound as a catalyst and contain an inorganic nucleating agent, 30 to 300 parts by weight of a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer into an aqueous suspension containing a dispersant;    impregnating the polyethylene-based resin beads with the styrene-based monomer under heating the resulting dispersion at such a temperature that the styrene-based monomer does not substantially polymerize;    performing first polymerization of the styrene-based monomer at a temperature of (T+10) to (T+35)° C. (where T° C. is a crystallization peak temperature of the polyethylene-based resin beads);    subsequent to the first polymerization, adding a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer and adjusting the temperature of the resulting dispersion to (T+10) to (T+35)° C. (where T° C. is a crystallization peak temperature of the polyethylene-based resin beads), so that impregnation of the polyethylene-based resin beads with the styrene-based monomer and second polymerization take place, wherein the total amount of the styrene-based monomers used in the first and second polymerization is 50 to 800 parts by weight relative to 100 parts by weight of the polyethylene-based resin beads; and    impregnating the resin-beads during or after the polymerization with a volatile blowing agent.    
   
   
       10 . A method for producing styrene-modified linear low-density polyethylene-based expandable resin beads according to  claim 9 , wherein the low-density polyethylene-based resin beads have a molecular weight distribution (Mw/Mn) of 1.5 to 3.5 measured by GPC and a density of 0.910 to 0.925 g/cm 3 .  
   
   
       11 . Styrene-modified linear low-density polyethylene-based resin beads, comprising 50 to 800 parts by weight of styrene-based resin relative to 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin which is polymerized using a metallocene compound as a catalyst, wherein styrene-based resin is dispersed a form particles in a beads, and the particle diameter is 0.8 μm or smaller in a surface region within at least 5 μm from the bead surface and a center region within a 5 μm radius from the bead center.  
   
   
       12 . Styrene-modified linear low-density polyethylene-based expandable resin beads, comprising a volatile blowing agent and 50 to 800 parts by weight of styrene-based resin relative to 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin which is polymerized using a metallocene compound as a catalyst, wherein styrene-based resin is dispersed a form particles in a beads, and the particle diameter is 0.8 μm or smaller in a surface region within at least 5 μm from the bead surface and a center region within a 5 μm radius from the bead center.  
   
   
       13 . Pre-expanded beads having a bulk density of 10 to 300 kg/m 3  obtained by pre-expanding the styrene-modified linear low-density polyethylene-based expandable resin beads of  claim 12 .  
   
   
       14 . An expanded molded article having a density of 10 to 300 kg/m 3  obtained by expansion molding of the pre-expanded beads of  claim 13.