Particulation of a metastable syrup

A continuous process comprising subjecting at least a portion of a metastable syrup consisting essentially of a continuous or co-continuous rubber phase and a discontinuous or co-continuous resin phase consisting essentially of:

• (i) from 99 to 80 weight % of a resin phase selected from the group consisting of:
• (a) homopolymers of C.sub.8-12 vinyl aromatic monomers which are unsubstituted or substituted by a C.sub.1-4 alkyl radical;
• (b) copolymers consisting essentially of:
• (1) from 50 to 90 weight % of one or more C.sub.8-12 vinyl aromatic monomers which are unsubstituted by a C.sub.1-4 alkyl radical;
• and
• (2) from 10 to 50 weight % of one or more monomers selected from the group consisting of C.sub.1-8 alkyl esters of acrylic or methacrylic acid, acrylonitrile, methacrylonitrile, and maleic anhydride;
• and
• (ii) from 1 to 20 weight % of a rubber phase selected from the group consisting of:
• (a) co- or homopolymers of C.sub.4-6 conjugated diolefins;
• (b) random, block, and tapered copolymers comprising from 10 to 80 weight % of one or more C.sub.8-12 vinyl aromatic monomers which are unsubstituted or substituted by a C.sub.1-4 alkyl radical;
• and from 20 to 90 weight % of one or more C.sub.6-8 conjugated diolefins;
• and
• (c) copolymers comprising from 5 to 50 weight % of acrylonitrile or methacrylonitrile and from 50 to 95 weight % of one or more C.sub.4-6 conjugated diolefins;
• which has been polymerized to from 5 to 75% conversion to a relatively uniform controlled shear field from 2 to 2,000 sec.sup.-1 by flowing said portion of said syrup through a device comprising:
• (I) a chamber having a circular cross section perpendicular to its longitudinal axis, at least one input port and at least one output port and a ratio of length to diameter from 0.5:1 to 3:1;
• (II) a cylinder within and occupying substantially the volume of said chamber said cylinder having a circular cross section perpendicular to its longitudinal axis, a surface closely conforming to the internal surface of the chamber except for a closely controlled clearance between the internal surface of the chamber and the external surface of the cylinder defined by the ratio of the radius of the chamber to the radius of the cylinder being from 0.993 to 0.875;
• and
• (III) means for rotating at least one of said cylinder and said chamber relative to each other,
• for a time of less than 10 minutes to cause phase inversion and the formation of a continuous resin phase and a dispersed rubber like composite phase having a volume average diameter from 0.01 to 15 microns.