Transcript Recycling - A Guide to the Continuous Regrind Process

Recycling - A Guide to
Continuous Regrind
Process
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More than just Waste???
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More than just Waste???
• Example 1: Using 1000kg/month of Acetal
(£2.84/Kg). Weight of the runner system is
100Kg (10% of Part weight), which means you
are throwing away £284/month and £3408/year.
• Example 2: Using 5000kg/month of PP
(£0.95/Kg). Weight of the runner system is
1000Kg (20% of Part weight), which means you
are throwing away £950/month and
£11,400/year.
Don’t forget Storage cost, Handling cost,
Collection cost, Transportation cost, Tax liability?
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Continuous Regrind Process
Feeder
(Dryer)
Runners
Parts
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Grinder
Virgin
resin
Melt Quality Regrind
% portion of resin that has been moulded x times
80
70
30% regrind
50% regrind
60
50
40
21
20
25
13
6
3
2
6
>1
0
1
3
2
1
>1
5
6
4
1 2 3 4 5 6 7 8
Times passed through the machine
For example, if 30% regrind is used in a continuous operation, only 2%
of the regrind has passed through the machine 4 times and less than 1 %
has passed through the machine 6 times or more.
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Example: Delrin* Acetal Resin
Number of times
through the cylinder
Melt index
10 times with
100% regrind
Increase < 10%
Tensile strength (yield) No difference
10 times with
50% regrind
Increase < 2%
No difference
Charpy notched impact Reduced by 20% Reduced by 2%
strength
Homopolymer
Copolymer
Degradation-1500 free molecules
Degradation-40 free molecules
free molecules
+ 2 shorter 40
chain
segments+
1500 free molecules
at degradation
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2 chain segment at
degradation
Example: Sarlink* TPR
Require grinders with properly adjusted, very sharp knives and
may need considerable cooling, especially for the softer grades.
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Example: Zytel* GR Nylon 6.6
Properties (%)
115
110
Elongation
105
Unnotched
Charpy
100
Tensile strength
95
Flex-modulus
80
0%
10%
20%
30%
40%
50%
60%
Regrind level
Glass fibre reinforced materials shows higher sensitivity to recycling, due to
the breakage of fibres during the regrinding process. Ideally ground hot to
minimise glass fibre breakage.
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Example: FR Plastics
This includes, but is not limited
to, the restricted use of regrind
thermoplastic material to
amounts less than 25% unless
specified in the individual
Recognitions.
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Keep in Mind
• Higher the quality of the regrind, higher the
quality of the finish part.
• Treat the regrind as if it’s virgin material.
• Maintain a constant ratio of virgin resin to
reground material.
• Particle size of reground material to be uniform
and similar to the virgin material.
• Make sure the grinder blades are kept sharp
and properly set to minimise fines.
• Clean grinders and regrind containers
frequently.
Finally, MUST establish the proper ratio of virgin
material to regrind, to give the right performance
for your particular application.
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A Polymer for Every
Application
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