Aldehyde content reduction process and recycled polyolefin with low aldehyde content

Patent metadata

Field	Value
Publication number	US-11518863-B2
Application number	US-202017624609-A
Country	US
Kind code	B2
Filing date	Jul 6, 2020
Priority date	Jul 8, 2019
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

Disclosed is a process for treating plastic waste chips containing a blend of polypropylene and polyethylene in an amount of at least 83.0 wt.-% to less than 100 wt.-% and further containing C7 to C11 aldehydes in an amount of 8000 ppb to 20000 ppb and limonene in an amount of 5 ppm to 500 ppm, the process comprising subjecting said plastic waste chips, in a fixed bed without stirring under standard pressure or reduced pressure, to a gas flow for achieving a Reynolds number in the range of 35 to 1200 at a temperature in the range of 20° C. to a point 10° C. below the Vicat softening point (10N, ISO 306) of said plastic waste and recovering the treated plastic waste chips containing C7 to C11 aldehydes in a total amount of 50 ppb to less than 5000 ppb limonene in an amount of 0.5 to 5 ppm.

First claim

The invention claimed is:

1. A process for treating plastic waste chips containing a blend of polypropylene and polyethylene in an amount of at least 83.0 wt.-% to less than 100 wt.-% and further containing C7 to C11 aldehydes and limonene, the process comprising the steps of:
(a) providing plastic waste chips in a treatment vessel having inlet and outlet for gas at opposite sides at upper and lower part section of the treatment vessel, whereby the plastic waste chips contain
C7 to C11 aldehydes in an amount of 8000 ppb to 20000 ppb as determined by HS-SPME-GC×GC-MS; and further contain
limonene in an amount of 5 ppm to 500 ppm as determined by HS-SPME-GC-MS

(b) optionally washing and drying said plastic waste chips of step (a);
(c) optionally preheating said plastic waste chips to a temperature in the range of 20° C. to a point 10° C. below the Vicat softening point (10N, ISO 306) of said plastic waste chips;
(d) subjecting said plastic waste chips, in a fixed bed without stirring under standard pressure or reduced pressure, to a gas flow for achieving a Reynolds number in the range of 35 to 1200 at a temperature in the range of 20° C. to a point 10° C. below the Vicat softening point (10N, ISO 306) of said plastic waste chips;
(e) recovering the treated plastic waste chips containing
C7 to C11 aldehydes in a total amount of 50 ppb to less than 5000 ppb as determined by HS-SPME-GC×GC-MS and
limonene in an amount of 0.5 to 5 ppm as determined by HS-SPME-GC-MS;

(f) subjecting said treated plastic waste chips of step (e) to an extrusion step yielding pellets; and
(g) recovering said pellets.

2. The process according to claim 1 , wherein the pressure of step (d) is within the range of 3 to 15 mbarg.

3. A process for treating plastic waste chips containing a blend of polypropylene and polyethylene in an amount of at least 83.0 wt.-% to less than 100 wt.-% and further containing C7 to C11 aldehydes and limonene, the process comprising the steps of:
(a) providing plastic waste chips, whereby the plastic waste chips contain
C7 to C11 aldehydes in an amount of 8000 ppb to 20.000 ppb as determined by HS-SPME-GC×GC-MS; and further contain
limonene in an amount of 5 ppm to 500 ppm as determined by HS-SPME-GC-MS

(b) subjecting said plastic waste chips to an extrusion step yielding raw pellets;
(c) placing said raw pellets in a treatment vessel having inlet and outlet for gas at opposite sides at upper and lower part section of the treatment vessel;
(d) optionally preheating said raw pellets to a temperature in the range of 20° C. to a point 10° C. below the Vicat softening point (10N, ISO 306) yielding preheated raw pellets;
(e) subjecting said raw pellets or said preheated raw pellets, in a fixed bed without stirring under standard pressure or reduced pressure, to a gas flow for achieving a Reynolds number in the range of 35 to 1200; at a temperature in the range of 20° C. to a point 10° C. below the Vicat softening point (10N, ISO 306) of said plastic waste chips
(f) recovering the treated pellets of step (e) containing
C7 to C11 aldehydes in a total amount of 50 ppb to less than 5000 ppb and
limonene in an amount of 0.5 ppm to less than 5 ppm as determined by HS-SPME-GC-MS.

4. The process according to claim 3 , wherein the pressure of step (e) is within the range of 3 to 15 mbarg.

5. The process according to claim 1 , wherein the gas is air.

6. The process according to claim 1 , wherein the recovered pellets as obtained from the process have an odor activity value (as defined in the specification) of less than 4000 as derived from the sum of heptanal, octanal, nonanal, decanal, undecanal, t-2-heptanal, t-2-octanal, t-2-nonenal, t-2-decenal, t-2-undecenal.

7. The process according to claim 1 , wherein the gas exiting the treatment vessel is subjected to a purification step by local cooling.

8. The process according to claim 1 , wherein the treatment gas is recycled.

9. The process according to claim 1 , wherein the treatment gas is discharged into the atmosphere.

10. The process according to claim 1 , wherein said plastic waste chips comprise
A-1) polypropylene and
A-2) polyethylene,
wherein the weight ratio of polypropylene A-1) to polyethylene A-2) is from 3:7 to 7:3 or
wherein the weight ratio of polypropylene A-1) to polyethylene A-2) is from 9:1 to 13:7.

11. The process according to claim 1 , wherein said plastic waste chips contain
(i) 0.1 wt.-% to 6.0 wt.-% polystyrene;
and/or
(ii) 0.1 wt.-% to 3.0 wt.-% talc;
and/or
(vii) 0.1 wt.-% to 5.0 wt.-% polyamide
and/or
(viii) 0.1 wt.-% to 3.0 wt.-% chalk.

12. The process according to claim 1 , wherein said treatment vessel is a silo.

13. The process according to claim 1 , wherein the gas is air and the treatment time is 0.5 to 3 hours.

14. The process according to claim 1 , wherein said plastic waste chips contain a recycled material that is recovered from a waste plastic material derived from post-consumer and/or industrial waste.

15. A polyolefin composition obtained by the process of claim 1 , containing
a blend of polypropylene and polyethylene in an amount of at least 83.0 wt.-% to less than 100 wt.-%, wherein the weight ratio of polypropylene to polyethylene is from 3:7 to 7:3 or
wherein the weight ratio of polypropylene to polyethylene is from 9:1 to 13:7;
and
0.1 to 6.0 wt.-% polystyrene;
and/or
0.1 to 3.0 wt.-% talc;
and/or
0.1 to 5.0 wt.-% polyamide
and/or
0.1 to 3.0 wt.-% chalk;
wherein the polyolefin composition contains
C7 to C11 aldehydes in an amount within the range of 50 ppb to less than 5000 ppb as determined by HS-SPME-GC×GC-MS and further contains limonene in an amount of 0.5 ppm to less than 5 ppm as determined by HS-SPME-GC-MS.

16. A polyolefin composition obtained by the process of claim 3 , containing
a blend of polypropylene and polyethylene in an amount of at least 83.0 wt.-% to less than 100 wt.-%, wherein the weight ratio of polypropylene to polyethylene is from 3:7 to 7:3 or
wherein the weight ratio of polypropylene to polyethylene is from 9:1 to 13:7;
and
0.1 to 6.0 wt.-% polystyrene;
and/or
0.1 to 3.0 wt.-% talc;
and/or
0.1 to 5.0 wt.-% polyamide
and/or
0.1 to 3.0 wt.-% chalk;
wherein the polyolefin composition contains
C7 to C11 aldehydes in an amount within the range of 50 ppb to less than 5000 ppb as determined by HS-SPME-GC×GC-MS and further contains limonene in an amount of 0.5 ppm to less than 5 ppm as determined by HS-SPME-GC-MS.

Assignees

• Borealis Ag

Inventors

• Vijay Sameer

Classifications

• B29B17/02 Primary

  Separating plastics from other materials · CPC title

• C08J2323/12

  Polypropene · CPC title

• B29B2017/0293

  Dissolving the materials in gases or liquids · CPC title

• Y02W30/62

  Plastics recycling; Rubber recycling · CPC title

• C08J2323/06

  Polyethene · CPC title