Closing the loop - TUT · PDF fileClosing the loop: 1 ... activation Reclaiming Rubber ... Breakdown of C-S bonds - Raney-Nickel - Alkali metals Reclaim Chemical devulcanization aids

1Closing the loop:Closing the loop:Rubber RecyclingRubber Recycling
Joint seminar Joint seminar
KumiKumi--instituutti & MOLinstituutti & MOL

2
Contents
- Introduction
- Present: Rubber crumb
Surface activated rubber crumb
Reclaim / devulcanizate
- Future

3
(V.L. Shulman, 2008, ETRA)
IntroductionUsed tires
EU countries: 2000: ca. 2,700,000 tons2006: ca. 3,200,000 tons
Retreading 12% Export 7%
Energy recovery31%
Material recycling 27 %
Landfill 20%Others 3%
2006800,000,000 tires/yearIncrease: 2%/year

4
ELV: EU legislation End of life vehicles
Introduction
Legislation
2003: Prohibition of landfill of whole tires (Dir. 1999/31/EC)
2006: < 15% landfill (ELV)2006: Prohibtion of landfill of shredded tires (Dir.1999/31/EC)
2015: < 5 % landfill (End of life vehicles EU legislation, Dir. 2000/53/EC)

5Introduction
Recycling loops
Increasing
degree
of
valorization
Energy consumption:New rubber: 115 J/kgRubber granulate: 2 J/kg
Material recycling
Compounds
Polymers
Feedstock recoveryMonomers
CnHm
Energy recovery
Vulcanized products
CO2 + H2O + energy

6
Vulcanizedrubber
Granulate
Powder
Surfaceactivation
Regeneration
Rubber
product
Buffings Rubber granulate, 5 mesh = 4 mm
Rubber powder, 16 mesh = 1.19 mm
Rubber powder, 30 mesh = 0.595 mm
Rubber powder
ambiently ground
2 m
cryogenically ground
10 m

7
Surface activated rubber powder
Vulcanizedrubber
Granulate
Powder
Surfaceactivation
Regeneration
Rubber
product
Chemical treatment
Biological treatment
Mechanical treatmentGranulate
Powder Physical treatment
Surfaceactivatedpowder

8
Surface activated rubber powder
Vulcanizedrubber
Granulate
Powder
Surfaceactivation
Regeneration
Rubber
product
Chemical treatment
Biological treatment
Mechanical treatmentGranulate
Powder Physical treatment
Surfaceactivatedpowder

9
Coating: + Polymer
Latex, low-molecular liquid polymer, polymer-oil blends
+ Curing additives
Swelling: + Oligomer, evtl. with functional groups+ Oil with (curing) additives
Grafting: + Silanes+ Ethylacrylate
Surface activated rubber powderChemical treatment

10
Technical Information Rubber Resources
10
20
30Tensile strength [MPa]
0
50
100
0 10 20 30 40 50
Concentration rubber crumb [%]-
Surface activated rubber crumb Untreated rubber crumb
Tear strength [N]0
10
20
Tensile strength [MPa]
Tear strength [N]
0
25
50
0 10 20 30 40 50
Concentration rubber crumb [%]
NR compound SBR compound
System: latex + curing agents
Powder: truck treads (70%NR/30%SBR)
(Surface activated) rubber powderInfluence on compound properties

11
50
100
150
200
Abrasion [mm3]
25
50
75Compression set (70) [%]
40
50
60
0 10 20 30 40 50Concentration rubber crumb [%]-
Rebound resilience (70C), [%]
Surface activated rubber crumb Untreated rubber crumb
0
100
200
Abrasion [mm]
0
50
100Compression set (70C) [%]
0 10 20 30 40 5030
40
50
Concentration rubber crumb [%]
Rebound resilience(70) [%]
NR compound SBR compound
(Surface activated) rubber powderInfluence on compound properties

12
Reclaim
Vulcanizedrubber
Granulate
Powder
Surfaceactivation
Reclaiming
Rubber
product
http://www.coe-nr.org
Definition reclaim: A process in which vulcanized rubber is converted into a material which can be
blended, processed, and cured again by using mechanical, thermal or chemical
processes
Devulcanization:Selective scission of sulfur crosslinks
Polymer
Crosslinks
Crosslink
scission
Polymer
scission

13
Granulate
PowderReclaim
Mechanicalreclaiming
Chemical devulcanization
Thermalreclaiming
ReclaimProcesses

14
Molecular weight
Initial MWDMWD after thermal breakdown MWD after mechanical breakdown
Softeners Polymers
mechanical thermal
120C Temperature
ReclaimThermomechanical breakdown
Vis
cosi
ty d
ecre
ase
Polymer degradation
Mechanical: + selective for longer chains- non-selective for polymer chains and crosslinks- reactive chain ends
Thermal: - non-selective in terms of chain length- non-selective for polymer chains and crosslinks- reactive chain ends

15
Granulate
PowderReclaim
Thermalreclaiming
ReclaimProcesses

16
Radical breakdown - Disulfides
Oxidation - Oxygen (air)
Nucleophilic breakdown - Mercaptanes
- Hydroxydes
- Amines
Breakdown of C-S bonds - Raney-Nickel
- Alkali metals
ReclaimChemical devulcanization aids

17
Granulate
PowderReclaim
Thermalreclaiming
ReclaimProcesses

18
Dijkhuis, K., thesis, 2008, ISBN 978-90-365-2643-2
EPDM roofing sheet compound, EV cured (short crosslinks)
200C 225C
250C 275C
CH3 (CH2)15 NH2
S S
CONHS
SNH
CO
(): HDA
(): DPDS
(): BAFD
ReclaimEffect of temperature, reclaiming aid and concentration

19ReclaimEffect of temperature, reclaiming aid and concentration
EPDM roofing sheet compound: conventionally cured (long crosslinks)
225C 250C 275C
CH3 (CH2)15 NH2 S S CONHS
SNH
CO
(): HDA (): DPDS (): BAFD

20ReclaimInfluence on compound properties (EPDM)
CH3 (CH2)15 NH2 S SCON
HSS
NH
CO(): HDA (): DPDS (): BAFD
Con
vent
iona
lly c
ured
EV c
ured
EPDM roofing sheet compound

21
ReclaimInfluence on compound properties (NR/SBR)
0 10 20 30 40
20
24
28
NR/SBR reclaim concentration [phr]
50
0 20 40 60 80 100
Rebound resilience [%]
Compression set [%]Abrasion [mm]
Tear strength [N]
% relative to basic compound
22% NR/SBR Reclaim
Basic compound (NR/SBR)
NR/SBR truck tire tread reclaim in a similar compound
Reclaiming aid: Diphenyldisulfide

22
In a blend with virgin rubber:
+ Shorter mixing, milling, extrusion cycles+ Lower processing temperature, less scorch+ Better tack+ Improved temperature resistance+ Higher green strength+ Easier escape of air from the mold+ Improved aging resistance
Reclaim(Dis)advantages
- Influence on property profile

23
Dijkhuis, K., thesis, ISBN 978-90-365-2643-2
Influencing factors for reclaiming efficiency:
- Temperature - Time - Shearing forces- Devulcanization aid- Restoration of double bonds
Shifting to devulcanization:
- Low temperatures- Low shearing forces - Appropriate devulcanization aid
The right choice of the devulcanization aid is crucial!
ReclaimMore efficient devulcanization

24
50% of recycled material back into (the original) rubber products
Shifting the balance between thermomechanical breakdown and chemical devulcanization to devulcanization
Emphasis on tire rubbers
- SBR (main tire rubber) is the most difficult elastomer to reclaim- Blend of elastomers can give only a best compromise
Rubber RecyclingThe future
Retreading 12% Export 7%
Energy recovery
28%
Material recycling
50%
Landfill 0%
Others 3%

25Closing the loop:Closing the loop:Rubber RecyclingRubber Recycling
Thank you for your attention!Thank you for your attention!
Closing the loop:
Rubber Recycling
Joint seminar
Kumi-instituutti & MOL
Contents
- Introduction
- Present: Rubber crumb
Surface activated rubber crumb
Reclaim / devulcanizate
- Future
(V.L. Shulman, 2008, ETRA)
Introduction
Used tires
EU countries:
2000: ca. 2,700,000 tons
2006: ca. 3,200,000 tons
800,000,000 tires/year
Increase: 2%/year
ELV: EU legislation End of life vehicles
Introduction
Legislation
2003: Prohibition of landfill of whole tires
(Dir. 1999/31/EC)
2006: < 15% landfill (ELV)
2006: Prohibtion of landfill of shredded tires (Dir.1999/31/EC)
2015: < 5 % landfill (End of life vehicles EU legislation,
Dir. 2000/53/EC)
Introduction
Recycling loops
Energy consumption:
New rubber: 115 J/kg
Rubber granulate: 2 J/kg
Vulcanized rubber
Granulate
Powder
Surface
activation

Documents

Closing the loop - TUT · PDF fileClosing the loop: 1 ... activation Reclaiming Rubber ... Breakdown of C-S bonds - Raney-Nickel - Alkali metals Reclaim Chemical devulcanization aids