Systems for producing superabsorbent polymers for use in agricultural applications
Systems for producing superabsorbent polymer particles for use in agricultural applications are disclosed. A monomer is graft polymerized onto a starch to form a starch graft copolymer. The moisture content of the starch graft copolymer is reduced through use of an extruder.
1. A system for producing superabsorbent polymer product, for use in agricultural applications, comprising:
a starch graft polymer polymerization dough having a moisture content by weight of about 80% formed by graft polymerizing a monomer onto a polysaccharide;
a hopper configured for receiving the starch graft polymerization dough;
a heated extruder in combination with the starch graft polymerization dough, wherein the starch graft polymerization dough has viscosity of between 0.5 million centipoise and to 2.5 million centipoise and wherein the heated extruder having a temperature of at least about 125° C., the heated extruder comprising:
i) an inlet for receiving the starch graft polymerization dough;
ii) an extrusion screw passing through a length of the heated extruder, wherein the extrusion screw is capable of rotating at a speed of 20 rpm to about 150 rpm and wherein the extrusion screw is at a pressure of between 25 psi and 40 psi; and
iii) an outlet configured to convert the starch graft polymerization dough into strands after the dough passes through the heated extruder; and
a pump feeding system configured to pump the starch graft polymerization dough from the hopper into the inlet.
2. The system of claim 1 , wherein the speed of the extrusion screw rotates at a speed of between about 20 rpm to about 150 rpm and the heat produced by the heated extruder a temperature of between 125° C. and 150° C.
3. The system of claim 2 , wherein the heated extruder further comprises at least one vent, such that a vacuum source is coupled to the at least one vent.
4. The system of claim 1 , wherein the extrusion screw comprises a double-screw system, wherein flights of each screw intermesh as they rotate.
5. The system of claim 1 , wherein the extrusion screw comprises multiple segments, such that at least two portions of a given segment of the extrusion screw have different flight configurations.
6. The system of claim 1 , wherein the heated extruder comprises a series of barrels in communication with each other, wherein the series of barrels comprises between 20 and 24 barrels arranged in series.
7. The system of claim 1 , wherein the pump feeding system is configured to deliver the polymerization dough to the inlet of the heated extruder under a pressure greater than atmospheric pressure.
8. The system of claim 1 , wherein the outlet comprises a die plate, the die plate configured to pass the polymerization dough after the dough passes through the heated extruder, and
wherein the heated extruder further comprises an air-cooled conveyor in communication with the outlet of the heated extruder, and configured to receive and cool the polymerization dough after exiting from the die plate.
9. The system of claim 1 , wherein the outlet comprises a die plate, the die plate configured to pass the polymerization dough after the dough passes through the heated extruder, and
wherein the heated extruder further comprises a granulator configured to granulate the polymerization dough, the granulator receiving the polymerization dough subsequent to the dough exiting from the die plate.
10. The system of claim 9 , further comprising:
a particle separation system to separate the granulated polymerization dough based on mesh size, the particle separation system receiving the granulated dough subsequent to the dough exiting the granulator.
11. The system of claim 10 , further comprising:
a centrifuge for centrifuging the granulated polymerization dough subsequent to the dough exiting the granulator and previous to the particle separation system receiving the granulated dough; and
a dryer for drying the granulated polymerization dough subsequent to the dough exiting the granulator and previous to the particle separation system receiving the granulated dough.
12. A system for reducing moisture of a starch graft polymer polymerization dough, the system comprising:
a polymerization dough having a moisture content by weight of about 80% formed from a starch graft copolymer formed by graft polymerizing a monomer onto a starch in the presence of an initiator;
a hopper configured for receiving the polymerization dough, the polymerization dough in combination with a system, the system comprising:
a heated extruder comprising:
i) a series of barrels in communication with each other, wherein a first barrel in the series of barrels is a feed barrel;
ii) an inlet in the feed barrel for receiving the polymerization dough;
iii) an extrusion screw passing through the series of barrels of the heated extruder; and
iv) an outlet configured to convert the polymerization dough into strands after the dough passes through the heated extruder; and
a pump feeding system configured to pump the polymerization dough from the hopper into the inlet at a pressure greater than atmospheric pressure, wherein after extrusion the polymerization dough has a moisture content about 40%;
wherein the temperature settings may vary from barrel to barrel and the temperature of each barrel may range from 50° C. and 160° C. and the extrusion screw rotates at a speed of between about 20 rpm to about 150 rpm.
13. The system of claim 12 , wherein at least one barrel of the series of barrels comprises an atmospheric vent and at least one barrel of the series of barrels comprises a vent compound to a vacuum pump.
14. The system of claim 12 , wherein the temperature of each barrel is about 125° C. to about 150° C.