Continuous process for preparing rubber modified high impact resin

In a process for continuously preparing rubber modified high impact resins which employs at least two polymerization reactors and a particle disperser and comprises the steps of (1) forming a starting solution obtained by dissolving a rubbery polymer in a starting monomer in which the rubber polymer is soluble, said starting monomer consisting of at least one aromatic vinyl monomer in an amount of from 47 to 99 parts by weight wherein the amounts of monomer(s) are based on a total amount of 100 parts by weight of the rubbery polymer, the starting monomer(s) and an organic solvent, if used, or a mixture of a radical polymerization initiator, at least one aromatic vinyl monomer and vinyl cyanide monomer with the ratio of aromatic vinyl monomer to cyanide monomer being 50:50 to 95:5, said starting monomer being continuously supplied into the first polymerization reactor;

• (2) conducting a polymerization reaction of the starting monomer in the first reactor so as to obtain a reaction liquid until the concentration of the polymer obtained by the polymerization, which concentration is required for converting the polymer into rubber particles dispersed in the reaction liquid, has been reached in the first reactor;
• (3) continuously removing the reaction liquid containing the particles of the rubbery polymer from the first reactor in an amount corresponding to the amount of the starting solution supplied into the first reactor;
• (4) feeding the reaction liquid taken out of the first reactor into a particle disperser, in which a shearing stirrer composed of rotatable agitator or cylindrical rotor is provided and rotated at high speed, for subjecting the particles of the rubbery polymer formed in the reaction liquid to the shearing treatment by the shearing stirrer in the particle disperser;
• (5) feeding the reaction liquid which has been subjected to the shearing treatment in the particle disperser into the second polymerization reactor in which the amount of the polymer formed from the starting monomer is maintained at a value of 25% or more as the conversion ratio of the starting monomer to the product, and continuing the polymerization reaction of the reaction liquid in the second reactor wherein the polymerizing reaction is conducted under conditions of (A) the following formula of
• V.sub.2 /V.sub.1 <0.2,
• wherein V.sub.1 is the volume occupied by the reaction liquid in the first reactor and V.sub.2 is the inner volume of the particle disperser;
• (B) the peripheral linear velocity of the agitator or rotor being rotated is at a value of 0.5 meter per second or faster;
• and (C) the following formulas of
• 1<X.sub.1 .ltoreq.20
• and
• 1.5 X.sub.1 -0.05 X.sup.2.sub.1 <X.sub.2 <4.5 X.sub.1 -0.05 X.sup.2.sub.1
• wherein X.sub.1 is the proportion of the rubbery polymer to the reaction liquid at the exit of the first reactor by weight percent and X.sub.2 is the ratio of the polymer formed from the starting monomer to the reaction liquid at the exit of the first reactor by weight percent.