Expandable vinylaromatic polymers and process for their preparation

Abstract

Expandable vinylaromatic polymers which comprise: a) a matrix obtained by polymerizing 50-100% by weight of one or more vinylaromatic monomers and 0.50% by weight of a copolymerizable monomer; b) 1-10% by weight, calculated with respect to the polymer (a), of an expanding agent englobed in the polymeric matrix; c) 0.05-25% by weight, calculated with respect to the polymer (a), of an inorganic filler homogeneously distributed in the polymeric matrix with a substantially spherical granulometry, an average diameter ranging from 0.01 to 100 μm, a refraction index higher than 1.6 and a white index, as defined in “Colour Index” (third edition published by the Society of Dyers and Colourists, 1982), equal to or lower than 22.

1 - 17 . (canceled)  
     
     
         18 . A process for preparing expandable vinyl aromatic polymers, comprising: 
 polymerizing one or more vinyl aromatic monomers present as an aqueous suspension in the presence of an inorganic filler having substantially spherical granulometry, an average diameter ranging from 0.01-100 micron, a refractive index higher than 1.6, and a white index equal to or lower than 22, and    adding an expanding agent to the aqueous suspension before, during or after the polymerizing,    wherein white index is defined in “Color Index” (3 rd  edition published by The Society of Dyers and Colorists, 1982).    
     
     
         19 . The process according to  claim 18 , wherein the aqueous suspension further comprises one or more polymerizable comonomers in an amount of up to 50% by weight based on the total weight of the monomers.  
     
     
         20 . The process according to  claim 18 , wherein the polymerizing is carried out to form substantially spherical beads of a polymer having an average diameter of from 0.2-2 mm and which comprise the inorganic filler homogeneously dispersed therein.  
     
     
         21 . The process according to  claim 18 , further comprising: 
 adding one or more flame-retarding agents in an amount of from 0.1-8% by weight based on the weight of the polymer formed in the process, during the polymerizing.    
     
     
         22 . The process according to  claim 21 , wherein the flame-retarding agent is at least one selected from the group consisting of a brominated aliphatic compound, a cycloaliphatic compound and an aromatic compound.  
     
     
         23 . The process as claimed in  claim 18 , wherein the expanding agent is added during the polymerization and the expanding agent is at least one selected from the group consisting of an aliphatic hydrocarbon, a cycloaliphatic hydrocarbon containing from 3 to 6 carbon atoms, a halogenated derivative of a aliphatic hydrocarbon containing from 1 to 3 carbon atoms, carbon dioxide, water and mixtures thereof.  
     
     
         24 . The process according to  claim 18 , wherein the polymerization in suspension takes place through a solution of vinyl aromatic polymer in the monomer, or mixture of monomers, wherein the concentration of polymer ranges from 1-30% by weight.  
     
     
         25 . A process for continuously preparing expandable vinyl aromatic polymer in bulk, comprising the following steps in series: 
 feeding the vinyl aromatic polymer to an extruder together with one or more inorganic fillers, wherein the inorganic filler has a substantially spherical granulometry, an average diameter ranging from 0.01-100 micron, a refractive index higher than 1.6, and a white index as defined in “Color Index” (3 rd  edition published by The Society of Dyers and Colorists, 1982) of 22 or lower;    heating the vinyl aromatic polymer to a temperature higher than the relative melting point of the vinyl aromatic polymer;    injecting one or more expanding agents into the molten vinyl aromatic polymer obtained by the heating; and    forming beads by passing the molten vinyl aromatic polymer through a dye,    wherein the beads are substantially spherical and have an average diameter of from 0.2-2 mm and the expanding agent is injected into the molten polymer before the molten polymer is passed through the dye.    
     
     
         26 . The process as claimed in  claim 25 , wherein the expanding agent is injected into the molten polymer as a mixture with one or more additives.  
     
     
         27 . The process as claimed in  claim 25 , wherein the beads formed by passing the molten vinyl aromatic polymer through the dye are expandable.  
     
     
         28 . The process as claimed in  claim 18 , further comprising: 
 carrying out the polymerizing to form expandable beads and pretreating the beads by    (i) coating the beads with a liquid antistatic agent; and    (ii) applying a coating to the treated beads wherein the coating comprises a mixture of mono-, di- and trimesters of glycerine with one or more fatty acids and one or more metallic stearates.    
     
     
         29 . The process as claimed in  claim 28 , wherein the liquid antistatic agent is at least one selected from the group consisting of an amine, a tertiary ethoxylated alkyl amine, and an ethylene oxide-propylene oxide copolymer.  
     
     
         30 . The process as claimed in  claim 29 , wherein the coating further comprises the inorganic filler.  
     
     
         31 . The process as claimed in  claim 28 , wherein the metallic stearate is at least one selected from the group consisting of zinc stearate and magnesium stearate.  
     
     
         32 . A process for continuously preparing expandable vinylaromatic polymers, which comprises the following steps in series: 
 feeding a vinylaromatic polymer, as described above, to an extruder, together with an inorganic filler, having a substantially spherical granulometry, an average diameter ranging from 0.01 to 100 μm, a refraction index higher than 1.6 and a white index, as defined in “Colour Index” (third edition published by The Society of Dyers and Colourists, 1982), equal to or lower than 22;    heating the vinylaromatic polymer to a temperature higher than the relative melting point;    injecting the expanding agent and possible additives, into the molten polymer, before extrusion through a die; and    forming beads, optionally expandable, through a die, in a substantially spherical form with an average diameter ranging from 0.2 to 2 mm.    
     
     
         33 . The process as claimed in  claim 32 , further comprising: 
 carrying out the polymerizing to form expandable beads and pretreating the beads by    (i) coating the beads with a liquid antistatic agent; and    (ii) applying a coating to the treated beads wherein the coating comprises a mixture of mono-, di- and tri-esters of glycerine with one or more fatty acids and one or more metallic stearates.    
     
     
         34 . The process as claimed in  claim 32 , wherein the liquid antistatic agent is at least one selected from the group consisting of an amine, a tertiary ethoxylated alkyl amine, and an ethylene oxide-propylene oxide copolymer.  
     
     
         35 . The process as claimed in  claim 32 , wherein the coating further comprises the inorganic filler.  
     
     
         36 . The process as claimed in  claim 32 , wherein the metallic stearate is at least one selected from the group consisting of zinc stearate and magnesium stearate.