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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
Technical Information Rubber Resources
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
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Granulate
PowderReclaim
Mechanicalreclaiming
Chemical devulcanization
Thermalreclaiming
ReclaimProcesses
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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
Mechanicalreclaiming
Chemical devulcanization
Thermalreclaiming
ReclaimProcesses
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Radical breakdown - Disulfides
Oxidation - Oxygen (air)
Nucleophilic breakdown - Mercaptanes
- Hydroxydes
- Amines
Breakdown of C-S bonds - Raney-Nickel
- Alkali metals
ReclaimChemical devulcanization aids
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Granulate
PowderReclaim
Mechanicalreclaiming
Chemical devulcanization
Thermalreclaiming
ReclaimProcesses
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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
Dijkhuis, K., thesis, 2008, ISBN 978-90-365-2643-2
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)
Dijkhuis, K., thesis, 2008, ISBN 978-90-365-2643-2
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
Technical Information Rubber Resources
ReclaimInfluence on compound properties (NR/SBR)
0 10 20 30 40
20
24
28
NR/SBR reclaim concentration [phr]
Tensile strength [MPa]
50
0 20 40 60 80 100
Rebound resilience [%]
Compression set [%]Abrasion [mm]
Tear strength [N]
Tensile strength [MPa]
% 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
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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
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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