Rubber-containing sytrenic resin and process for producing the same

Abstract

The rubber-containing styrenic resin of the present invention comprises a styrenic resin matrix and a rubber component dispersed in particles. In the resin, the graft ratio of a styrenic monomer relative to the rubber component is not less than 1, the particle size of the dispersed rubber component is 0.1 to 3 μm, and the following equation (1) is satisfied: Mn=aT+b   (1) wherein Mn is the number average molecular weight of the matrix resin; T is the conversion of the styrenic monomer; a is a constant greater than 0; and b is a constant of 0 or greater. The rubber component may be a butadiene-series rubber. The particle-size distribution of the dispersed rubber component may have, for example, two peaks. Such styrenic resin can be produced by, in the presence of a rubber component, polymerizing at least a styrenic monomer at a graft ratio of not less than 1 under such conditions that the relationship between the conversion T of the styrenic monomer and the number average molecular weight Mn of the polymer can be approximated by a linear equation. According to the present invention, the morphology and the particle size of rubber particles dispersed in a styrenic resin are controllable.

What is claimed is:  
     
         1 . A process for producing a rubber-containing styrenic resin, which comprises polymerizing at least a styrenic monomer in the presence of a rubber component at a graft ratio of not less than 1 under such conditions that the relationship between the conversion T of the styrenic monomer and the number average molecular weight Mn of the resultant polymer can be approximated by a linear equation.  
     
     
         2 . A process according to  claim 1  which provides a rubber-containing styrenic resin in which the rubber component having a mean particle size of 0.1 to 3 μm is dispersed.  
     
     
         3 . A process according to  claim 1 , wherein the polymerization is carried out in the presence of a polymerization initiator and/or at least one additive selected from the group consisting of a hydroxyamine, a nitroso compound and a nitrone compound represented by the following formulae (2) to (4) respectively:  
       
         
           
           
               
               
           
         
         wherein R 1  to R 5  are the same or different from each other, each representing a hydrogen atom, an alkyl group, an alkoxy group, an acyl group, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group; the groups R 1  and R 2  and the groups R 4  and R 5  may bond together to form rings individually; and R 3  may be a group represented by the following formula (3a):  
         
           
             
             
                 
                 
             
           
         
         wherein R 3a  to R 3c  are the same or different from each other, each representing a hydrogen atom, an alkyl group, or an aryl group; and at least two of the groups R 3a  to R 3c  may bond together to form a ring.  
       
     
     
         4 . A process according to  claim 3 , wherein the additive is at least one member selected from the group consisting of an N,N-diC 1-4 alkylhydroxylamine, an aromatic dicarboxylic acid imide, a compound shown by the formula (3a) in which at least two of the groups R 3a  to R 3c  are the same or different alkyl groups, a nitroso-t-alkane, nitrosobenzene, a dimer of a nitroso compound, an N-t-C 4-8 alkyl-α-arylnitrone, a pyrroline-N-oxide, and a pyridine-N-oxide.  
     
     
         5 . A process according to  claim 3 , wherein the ratio of the additive to the polymerization initiator is the former/the latter (molar ratio)=0.01/1 to 100/1.