Process of producing PCR pellets
View Patent ↗A process for producing, from PCR polyolefin feedstock, pellets which are suitable for molding into useful articles suitable for food contact and other applications wherein feedstock fragrances are not desirable.
1. A process for producing fragrance-free pellets having a limonene content of less than about 320 parts per billion from post-consumer recyclable (PCR) polyolefin plastic comprising the steps, performed in the following sequence, of
(i) extruding odiferous PCR polyolefin chips to form odiferous pellets;
(ii) contacting the odiferous pellets with hot air at a temperature of about 50° C. to about 125° C. for about 3 to about 10 hours in a vessel to form fragrance-free pellets;
(iii) flowing the fragrance-free pellets vertically downward to a common outlet; and
(iv) discharging the fragrance-free pellets in discrete slugs from the vessel in sequential controlled quantities.
2. The process of claim 1 wherein said odiferous chips are directly subjected to said de-volatizing step without any intervening storage.
3. The process according to claim 1 where the pellets are flowed downwardly through said vessel by gravity and are contacted by hot air flowed upwardly in said vessel at a superficial velocity in a range of about 1.00 ft/sec to about 2.10 ft/sec and at a temperature in a range of about 90° C. to about 125° C.
4. The process according to claim 1 where the pellets are stirred continually in a rotary manner as they descend in the vessel.
5. The process according to claim 1 wherein the pellets are discharged from the vessel in sequential controlled quantities to control the required duration of residence in the vessel.
6. The process according to claim 1 including the step of directing the flow of pellets in a lateral direction between said stirring step and said sequential discharging step.
7. In a process for de-volatizing PCR polyolefin plastic pellets in a vessel having tapered bottom wall ( 21 ) with a central outlet ( 22 ), wherein the pellets are permitted to flow downwardly by gravity in a loose mass while being stirred, and are contacted by hot gas flowing upwarding through the mass of the pellets, the improvement comprising the step of controlling the downward movement of the mass of pellets above the outlet ( 22 ) while discharging the pellets in discrete slugs of de-volatized pellets.
8. The process according to claim 7 wherein said controlling step includes the step of displacing pellets laterally by a baffle ( 25 ) located above the outlet ( 22 ).
9. The process according to claim 8 wherein said mass of pellets is disposed in a cylindrical formation as it descends downwardly, and said displacing step is performed centrally of the mass above the outlet ( 22 ).
10. The process according to claim 9 wherein the baffle ( 25 ) has an angle of inclination in a range of between about 30 degrees to about 70 degrees.
11. The process according to claim 9 where the baffle ( 25 ) has an outer diameter which is about ⅙ to about 1/9 of the inner diameter of the vessel.