Apparatus for mixing thermoplastified synthetic resins

An apparatus for blending a pumpable additive with a flow of a thermoplastified synthetic resin, comprising:

• a worm press having:
• a cylinder,
• a plastifying screw rotatable in said cylinder and generating a flow of a thermoplastified synthetic resin fed to said worm press whereby said synthetic resin is thermoplastified therein and displaced in a flow along said worm press, and
• a worm-press drive connected to said screw for driving same;
• at least one mixing device communicating with said worm press, receiving said flow therefrom and driven independently from said worm press, said mixing device comprising:
• a rotor along the path of said flow rotating with having a peripheral surface,
• a stator surrounding said rotor having a peripheral surface juxtaposed with said peripheral surface of said rotor so that said surfaces define an axially -extending annular gap between them, each of said surface being formed with a plurality of angularly equispaced axially extending rows of axially elongated mixing chambers of identical outline each with semicircular ends of a given radius, the mixing chambers of said surface of said rotor being axially offset from the mixing chambers of said surface of said stator by substantially half the length of said mixing chambers, said mixing chambers being troughs of circular arc segmental cross section with radii of curvature equal to said given radius and depths less than said given radius, the length of each mixing chamber being three to four times said given radius, the mixing chambers of successive rows of each surface being separated by webs having a thickness less than half of said given radius and said gap 33 having a gap width generating a shear velocity gradient sufficient to effect intimate mixing in said gap of said flow as said flow passes through said gap, and
• a mixing-unit drive operatively connected with said rotor for driving same independently of said screw;
• and
• a pump communicating with a source of a pumpable additive to be admixed with said flow connected to said stator at at least one location around said rotor and at an upstream end of said gap, for feeding said pumpable additive into said gap for admixture to said thermoplastified synthetic resin, thereby blending said additive with said thermoplastified synthetic resin.