Expandable modified resin beads, expanded modified resin beads, and foamed molded article formed from expanded modified resin beads

Abstract

Disclosed is expandable modified resin beads ( 1 ), comprising a modified resin as a base resin in which a dispersion phase ( 3 ) containing a styrene resin as a major component is dispersed in a continuous phase ( 2 ) containing an olefin resin as a major component, and a physical blowing agent. Further disclosed are expanded modified resin beads obtained by expanding the expandable modified resin beads ( 1 ), and a foamed molded article formed from the expanded modified resin beads obtained by molding the expanded modified resin beads in a mold. A volume average diameter of the dispersion phase ( 3 ) dispersed in the continuous phase ( 2 ) is 0.55 μm or more. The expandable modified resin beads ( 1 ) have, as a base resin, the modified resin contains 80 to 50 parts by mass of the styrene resin with respect to 20 to 50 parts by mass parts of the olefin resins.

1 . An expandable modified resin bead, comprising:
 a modified resin as a base resin, which comprises a dispersion phase dispersed in a continuous phase; and   a physical blowing agent,   wherein the dispersion phase comprises a styrene resin as a major component,   the continuous phase comprises an olefin resin as a major component, and   a volume average diameter of the dispersion phase dispersed in the continuous phase is 0.55 μm or more.   
     
     
         2 . The bead of  claim 1 ,
 wherein the modified resin comprises from 80 to 50 parts by mass of the styrene resin and from 20 to 50 parts by mass of the olefin resin, based on a total amount of the styrene resin and the olefin resin of 100 parts by mass,   the dispersion phase comprises a dispersion diameter-enlarging agent comprising a thermoplastic resin capable of enlarging the volume average diameter of the dispersion phase,   a content of the dispersion diameter-enlarging agent in the modified resin is from 1 to 10 parts by mass with respect to 100 parts by mass of the olefin resin, and   the bead satisfies a relationship 1.25 V<V 0 , wherein V (g/hour) is a blowing agent-decrease rate of the bead, and V 0  (g/hour) is a blowing agent-decrease rate of an expandable modified resin bead not comprising the dispersion diameter-enlarging agent.   
     
     
         3 . The bead of  claim 2 ,
 wherein the thermoplastic resin has a solubility parameter of 15 MPa 1/2  to 25 MPa 1/2 .   
     
     
         4 . The bead of  claim 2 ,
 wherein the dispersion diameter-enlarging agent comprises at least one substance selected from the group consisting of a styrene resin different from the styrene resin that is the major component of the dispersion phase, a styrene-based elastomer, and a vinyl chloride resin.   
     
     
         5 . The bead of  claim 1 , wherein the olefin resin comprises a linear low density polyethylene, an ethylene-vinyl acetate copolymer, or both. 
     
     
         6 . The bead of  claim 1 , wherein the physical blowing agent comprises:
 a hydrocarbon having from 4 to 6 carbon atoms and at least one substance selected from the group consisting of isobutane, n-pentane, and isopentane   wherein a content of the at least one substance is 20 parts by mass or more with respect to 100 parts by mass of a total amount of the physical blowing agent.   
     
     
         7 . The bead of  claim 1 , wherein a content of the physical blowing agent is from 5 to 30 parts by mass with respect to 100 parts by mass of the modified resin. 
     
     
         8 . An expanded modified resin bead, obtained by heating the bead of  claim 1  in a heating medium to foam and expand the bead. 
     
     
         9 . A foamed molded article, comprising:
 an expanded modified resin bead, obtained by molding the bead of  claim 8  in a mold.   
     
     
         10 . The bead of  claim 1 , wherein the volume average diameter of the dispersion phase is 0.6 μm or more. 
     
     
         11 . The bead of  claim 1 , wherein the volume average diameter of the dispersion phase is 10 μm or less. 
     
     
         12 . The bead of  claim 2 ,
 wherein the modified resin comprises from 75 to 55 parts by mass of the styrene resin and from 25 to 45 parts by mass of the olefin resin, based on a total amount of the styrene resin and the olefin resin of 100 parts by mass.   
     
     
         13 . The bead of  claim 12 ,
 wherein the modified resin comprises from 75 to 65 parts by mass of the styrene resin and from 25 to 35 parts by mass of the olefin resin, based on a total amount of the styrene resin and the olefin resin of 100 parts by mass.   
     
     
         14 . The bead of  claim 2 ,
 wherein the dispersion diameter-enlarging agent has a melt mass flow rate (MFR (200° C., 5 kgf)) of from 1 g/10 min to 500 g/10 min.   
     
     
         15 . The bead of  claim 14 ,
 wherein the MFR (200° C., 5 kgf) is from 2 g/10 min to 200 g/10 min.   
     
     
         16 . The bead of  claim 2 ,
 wherein the dispersion diameter-enlarging agent comprises an acrylonitrile-styrene copolymer.   
     
     
         17 . The bead of  claim 16 ,
 wherein a weight average molecular weight of the acrylonitrile-styrene copolymer is from 50,000 to 150,000.   
     
     
         18 . The bead of  claim 17 ,
 wherein a weight average molecular weight of the acrylonitrile-styrene copolymer is from 60,000 to 120,000.   
     
     
         19 . The bead of  claim 2 ,
 wherein a content of the dispersion diameter-enlarging agent in the modified resin is from 1 to 10 parts by mass with respect to 100 parts by mass of the olefin resin.   
     
     
         20 . The bead of  claim 19 ,
 wherein the content of the dispersion diameter-enlarging agent in the modified resin is from 3 to 7 parts by mass with respect to 100 parts by mass of the olefin resin