www.distrupol.com recycling - a guide to continuous regrind process

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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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Grinder

Feeder(Dryer)

Virginresin

Runners

Parts

Continuous Regrind Process

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70

1

21

2

6

3

3

4

2

5

> 1

6

50

1

25

2

13

3

6

4

3

5

2

6

1

7

> 1

80

20

40

60

80

% portion of resin that has been moulded x times

Times passed through the machine

30% regrind 50% regrind

Melt Quality Regrind

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

10 times with 100% regrind

10 times with 50% regrind

Melt index Increase < 10% Increase < 2%

Tensile strength (yield) No difference No difference

Charpy notched impact strength

Reduced by 20% Reduced by 2%

1500 free moleculesat degradation

1500 free moleculesat degradation

40 free molecules +2 chain segment at

degradation

40 free molecules +2 chain segment at

degradation

Homopolymer Copolymer

Degradation-1500 free molecules Degradation-40 free molecules+ 2 shorter chain segments

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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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95

100

105

110

115Properties (%)

Regrind level

800% 10% 20% 30% 40% 50% 60%

Flex-modulus

Tensile strength

Elongation

UnnotchedCharpy

Example: Zytel* GR Nylon 6.6

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 limitedto, the restricted use of regrindthermoplastic material to amounts less than 25% unlessspecified in the individualRecognitions.

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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 Finally, MUST establish the proper ratio of virgin material to regrind, to give the right virgin material to regrind, to give the right performance for your particular application.performance for your particular application.

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A Polymer for Every Application