Rubber-reinforced vinyl aromatic polymers

Abstract

Rubber-reinforced vinyl aromatic polymers having a strictly bimodal morphology, comprising from 55 to 90% by weight of a rigid polymeric matrix and from 10 to 45% by weight of a rubbery phase dispersed inside said rigid polymeric matrix, in the form of grafted and occluded particles and wherein said rubber particles consist of from 60 to 99% by weight of particles with a capsule or “core-shell” morphology and from 1 to 40% by weight of particles with a “salami” morphology, said percentages being measured on the basis of the weight of the rubber particles only.

1 - 17 . (canceled) 
     
     
         18 . A reinforced vinyl aromatic (co)polymer, consisting of:
 from 55 to 90% by weight of a rigid polymeric matrix and   from 10 to 45% by weight of grafted and occluded rubber particles dispersed inside the rigid polymeric matrix;   wherein the grafted and occluded rubber particles have a strictly bimodal morphology consisting of from 60 to 99% by weight of particles with a capsule or core-shell morphology and from 1 to 40% by weight of particles with a salami morphology, said percentages being measured on the basis of the weight of the rubber particles only; and   wherein the difference between the solubility parameter (δ 1 ) according to Hildebrand of the elastomer which produces the capsule or core-shell morphology of the rubbery particles and the solubility parameter (δ 2 ) according to Hildebrand of the elastomer which produces the salami morphology of the rubbery particles, is higher than or equal to 0.5 (δ 1 −δ 1 ≧0.5).   
     
     
         19 . The reinforced vinyl aromatic (co)polymer according to  claim 18 , wherein
 the particles with capsule or core-shell morphology have an average diameter ranging from 0.10 to 0.30 μm, and   the particles with a salami morphology have an average diameter ranging from 1 to 5 μm.   
     
     
         20 . The reinforced vinyl aromatic (co)polymer according to  claim 18 , wherein the grafted and occluded particles with a capsule or core-shell morphology are elastomers selected from homopolymers and copolymers of olefins or 1,3-alkadienes containing 40-100% by weight of 1,3-alkadiene monomer and 0-60% by weight of one or more mono-ethylenically unsaturated monomers. 
     
     
         21 . The reinforced vinyl aromatic (co)polymer according to  claim 20 , wherein the elastomers producing the particles with a capsule or core-shell morphology are copolymers selected from linear diblock rubbers of the S-B type, wherein S represents a polystyrene block having an average molecular weight Mw between 5,000 and 80,000, and B represents a poly-butadiene block with an average molecular weight Mw between 2,000 and 250,000. 
     
     
         22 . The reinforced vinyl aromatic (co)polymer according to  claim 21 , wherein the amount of the S block ranges from 10 to 50% by weight with respect to the total S-B rubber. 
     
     
         23 . The reinforced vinyl aromatic (co)polymer according to  claim 22 , wherein the elastomers producing the particles with a capsule or core-shell morphology are copolymers selected from styrene-butadiene block copolymers having a styrene content equal to 40% by weight and a viscosity in solution, measured at 23° C. in a 5% by weight styrene solution, ranging from 35 to 50 cPs. 
     
     
         24 . The reinforced vinyl aromatic (co)polymer according to  claim 18 , wherein the elastomers producing the particles with a salami morphology are selected from homopolymers and copolymers of olefins or 1,3 alkadienes incompatible with the homopolymers or copolymers which produce the particles with the capsule or core-shell morphology. 
     
     
         25 . The reinforced vinyl aromatic (co)polymer according to  claim 24 , wherein the elastomers producing the particles with a salami morphology are selected from polyisoprenes with a viscosity in solution, measured at 23° C. in a 5% by weight styrene solution, ranging from 100 to 1000 cPs. 
     
     
         26 . A rubber-reinforced vinyl aromatic (co)polymer consisting of:
 from 55 to 90% by weight of rigid polymeric matrix and   from 10 to 45% by weight of grafted and occluded particles having a strictly bimodal morphology consisting of:
 from 60 to 99% by weight of particles with a capsule or core-shell morphology and 
 from 1 to 40% by weight of particles with a salami morphology; 
   which is made by a mass-continuous process comprising:   a. preparing a solution comprising:
 from 3 to 20% by weight of a rubber having a solubility parameter (δ 1 ) selected from the group consisting of homopolymers and copolymers of 1,3-alkadienes containing 40-100% by weight of 1,3-alkadiene monomer and 0-60% by weight of one or more mono-ethylenically unsaturated monomers, 
   from 0.05 to 8.0% by weight of a rubber having a solubility parameter (δ 2 ) selected from the group consisting of homopolymers and copolymers of olefins or 1,3-alkadienes, and   at least one vinyl aromatic monomer;   b. polymerizing the solution at a temperature ranging from 50 to 250° C., optionally in the presence of polymerization initiators and/or chain transfer agents, to obtain a rubber-reinforced vinyl aromatic (co)polymer with a strictly bimodal morphology; and   c. recovering the rubber-reinforced vinyl aromatic (co)polymer thus obtained;   wherein
   δ 1 −δ 2 ≧0.5.
 
   
     
     
         27 . A rubber-reinforced vinyl aromatic (co)polymer obtained by a mass-continuous process comprising:
 i) preparing a solution comprising:   from 3 to 20% by weight of a rubber having a solubility parameter (δ 1 ), selected from the group consisting of homopolymers and copolymers of 1,3-alkadienes containing 40-100% by weight of 1,3-alkadiene monomer and 0-60% by weight of one or more mono-ethylenically unsaturated monomers, from 0.05 to 8.0% by weight of a rubber having a solubility parameter (δ 2 ) selected from the group consisting of homopolymers and copolymers of olefins or 1,3-alkadienes   at least one vinyl aromatic monomer;   ii) pre-polymerizing the solution at a temperature ranging from 50 to 250° C. in the presence of polymerization initiators and/or chain transfer agents, until phase inversion takes place;   iii) after phase inversion, completing polymerization in aqueous phase in the presence of suspending agents to obtain the rubber-reinforced vinyl aromatic (co)polymer with a strictly bimodal morphology;   wherein
   δ 1 −δ 2 0.5, and
 
   the recovered rubber-reinforced vinyl aromatic (co)polymer consists of:   from 55 to 90% by weight of rigid polymeric matrix and   from 10 to 45% by weight of grafted and occluded particles having a strictly bimodal morphology, consisting of:
 from 60 to 99% by weight of particles with a capsule or core-shell morphology and 
 from 1 to 40% by weight of particles with a salami morphology. 
   
     
     
         28 . The reinforced vinyl aromatic (co)polymer according to  claim 26 , wherein
 the particles with a core-shell morphology have an average diameter ranging from 0.10 to 0.30 μm, and   the particles with a salami morphology have an average diameter ranging from 1 to 5 μm.   
     
     
         29 . The reinforced vinyl aromatic (co)polymer according to  claim 26 , wherein the rubber having a solubility parameter (δ 1 ) is a linear diblock rubber of an S-B type, wherein S is a polystyrene block having an average molecular weight Mw between 5,000 and 80,000, and B is a poly-butadiene block with an average molecular weight Mw between 2,000 and 250,000. 
     
     
         30 . The reinforced vinyl aromatic (co)polymer according to  claim 29 , wherein an amount of the polystyrene S block is from 10 to 50% by weight with respect to the totals weight of the S-B rubber. 
     
     
         31 . The rubber-reinforced vinyl aromatic (co)polymer according to  claim 30 , wherein
 the polystyrene S block content is 40% by weight and   a viscosity in solution, measured at 23° C. in a 5% by weight styrene solution, is from 35 to 50 cPs.   
     
     
         32 . The rubber-reinforced vinyl aromatic (co)polymer according to  claim 26 , wherein
 the rubber having a solubility parameter (δ 2 ) is polyisoprene, and   a viscosity in solution, measured at 23° C. in a 5% by weight styrene solution, is from 100 to 1000 cPs.   
     
     
         33 . The rubber-reinforced vinyl aromatic (co)polymer according to  claim 26 , wherein
 wherein the vinyl aromatic monomer is represented by formula (I):   
       
         
           
           
               
               
           
         
         wherein R is a hydrogen or a methyl group, n is zero or an integer ranging from 1 to 5 and Y is a halogen such as chlorine or bromine, or an alkyl or alkoxyl radical having from 1 to 4 carbon atoms.