US 6,365,710 B1 · Method for removing volatile components from solid polymeric materials

Abstract

A method for removing volatile components from wet, solid polymeric materials on a vacuum vented extruder is described. Polymeric materials containing substantial amounts of water, 1-20 % by weight, are rapidly converted to polymer compositions containing less than about 0.5% by weight water at high throughput rates while avoiding complications resulting from excessive steam backflow through the extruder feed throat. The method utilizes a screw design comprising only forward flighted screw elements in an initial polymer melting and kneading zone. Steam generated as the polymer is heated and sheared flows downstream to a first vacuum vent for removal. The partially devolatilized polymer melt is then subjected to additional kneading and vacuum venting. The claimed method converts wet polycarbonate powder containing residual methylene chloride to essentially dry polycarbonate powder containing less than about 1 ppm methylene chloride.

Claims63

Dependent claims

A method for removing volatile components from a solid polymeric material, said method comprising:

Step (A) introducing a solid polymeric material comprising water into an extruder, said extruder comprising;
(i) a primary kneading and melting section, said primary kneading and melting section consisting essentially of forward flighted kneading elements and optionally, forward flighted conveying elements;
(ii) a first vacuum vent located downstream of said primary kneading and melting section;
(iii) a secondary melt kneading section located downstream of the first vacuum vent;
and
(iv) a second vacuum vent located downstream of said secondary melt kneading section;
Step (B) heating and shearing said polymeric material in said primary kneading and melting section to form a polymer melt comprising water;
Step (C) removing a portion of the water from the polymer melt through said first vacuum vent to form a partially devolatilized polymer melt;
Step (D) subjecting the partially devolatilized polymer melt to additional melt kneading in a secondary melt kneading section;
and
Step (E) removing an additional amount of water from the partially devolatilized polymer melt at said second vacuum vent.

8 more elements

A method for removing volatile components from a solid polymeric material, said method comprising:

Step (A) introducing a solid polymeric material comprising water into an extruder, said extruder having a feed rate at which said polymeric material is introduced into the extruder, said extruder having a screw speed, said extruder having a power utilization and a maximum power utilization, said extruder comprising;
(i) a primary kneading and melting section, said primary kneading and melting section consisting essentially of forward flighted kneading elements and optionally, forward flighted conveying elements;
(ii) a first vacuum vent located downstream of said primary kneading and melting section;
(iii) a secondary melt kneading section located downstream of the first vacuum vent;
and
(iv) a second vacuum vent located downstream of said secondary melt kneading section;
Step (B) heating and shearing said polymeric material in said primary kneading and melting section to form a polymer melt comprising water;
Step (C) removing a portion of the water from the polymer melt through said first vacuum vent to form a partially devolatilized polymer melt;
Step (D) subjecting the partially devolatilized polymer melt to additional melt kneading in a secondary melt kneading section;
Step (E) removing an additional amount of water from the partially devolatilized polymer melt at said second vacuum vent;
and
Step (F) controlling the screw speed and feed rate such that the extruder power utilization is between about 50 and about 100 percent of s aid maximum power utilization.

9 more elements

Dependencies are inferred from the claim text.

Method for removing volatile components from solid polymeric materials

Life of this patent

Method for removing volatile components from solid polymeric materials

Life of this patent

Abstract

Claims63