Assessment of Methods for the Measurement of Macrostickies in - - PowerPoint PPT Presentation

10/17/2007 www.fpinnovations.ca 1

Assessment of Methods for the Measurement of Macrostickies in Recycled Pulps

Bruce Sitholé & Denise Filion

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Outline

• Classification of stickies
• Assessing quality of DIP
• How are stickies measured
• Evaluation of different methodologies

– Their merits and demerits

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Classification of stickies

• Doshi and Dyer classified stickies by

physical and chemical properties

– Chemistry (PSA, hot melts, or both) – Screening (macro and micro) – Behaviour (viscoelastic and rigid) – External factors (primary and secondary) – Association (bound to fibres and free) – Compatibility (recycle-compatible & recycle- incompatible) – Visibility (visible and sub-visible)

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Classification of stickies

• More commonly classified into 2 broad

classes:

– Macrostickies – Microstickies

• Later, also classified into:

– Macro – Micro – Colloidal

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Classification of stickies

• Macrostickies

– Solid particles resulting from incomplete disintegration during repulping – Particle size exceeds 100 µm – Can be removed by coarse screening – Major sources

• Hot melts, PSAs

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Classification of stickies

• Microstickies

– Particles 100-1 µm range – Sources

• Small adhesives particles
• Coating binders
• Ink resins

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Classification of stickies

• Colloidal

– Particles below 1 µm – Particles of insoluble wood resin, SBR, PVA, latexes, emulsified oils

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Assessing the quality of DIP

• Variable and mill specific
• Commonly assessed by amount and

size of particles

• Acceptable pulps

– 10 or less particles per 100 g OD pulp – Maxim size of 0.4 mm2 per particle

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Assessing the quality of DIP

• Quality objectives of recycled

printing grade paper

<150 mm2/m2 <100 mm2/m2 >62% ISO <10% Impurities Stickies, hot melts Brightness Filler Specifications Parameter

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Assessing the quality of DIP

• It is evident that macrostickies

define the quality of DIP recycled printing papers

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How are they measured?

• Literature review and discussions with

mill personnel show large variety in methods used

• The methods are based on three

principles –Collection –Transfer –Measurement

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Measurement of stickies

Pulp sample Disintegration Screening (150 or 100 µm) Collect on filter paper

• r screen

Coating, pressure, temperature Blotter, couch, brushing Copy paper, laminator Manual counting, Image analysis

Step 1: collection Step 3: measurement Step 2: transfer

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Measurement of stickies

• Significant differences in the details of

the three steps

• Therefore, we evaluated the pros and

cons of the methods

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Objective

• Evaluate the different methodologies
• Recommend which one(s) to use for

evaluating the quality of recycled pulps

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Previous work

• Doshi et al (2003) compared four

methods for measuring macrostickies

• Model and real samples were analysed

by 4 labs –Black ink method –INGEDE method –Enzyme digestion method –Blue dye method

• All methods used image analysis

–Average # and size of contaminants

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Previous work

• Conclusion

–considerable variations in actual values

• f stickies area reported by the

participating groups

• Not surprising due to significant differences in the

methods used to measure the concentration of macrostickies

–excellent linear correlation among all methods for both laboratory as well as mill samples

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Previous work

• Conclusion

–Any one of the methods was suitable for monitoring stickies content –But one could not compare actual values from the different labs as they may vary significantly

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Our approach

• Samples analysed by the same

personnel in one laboratory

• Helps in assessing the merits and

demerits of the different methodologies

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Samples

25 g OD 50 g OD 50 g OD 25g OD ONP/magazine (70:30) ONP (100%) MOW OCC DIP news tissue paper recycled board Mill1 Mill2 Mill3 Mill4 Amount

• f sample

Fibre source Type of mill Site

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Methods used

• TAPPI T277
• Total count
• Stickies count
• Wet specimen
• Blue dye
• Lamination
• Transparency film
• Reference method

– Manual observation and counting

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Sample preparation

• Collection step

–Pulmac Masterscreen

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Analysis

Physical properties Quantification Scanner

Characterization of macrostickies

(tacky, gooey, powdery, etc) (number/area of particles)

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Methods used: TAPPI T277

• Collect rejects on a black filter paper
• Place coated paper on top of the rejects
• Sandwich filter paper and coated paper

between two blotters

• Heat and press for 10 min
• Wash to remove other material
• Cover with silicon release paper: heat

and dry

• this transfers the silicone onto the stickies to

make them more visible for image analysis.

• Eliminate fibres prior to scanning and

image analysis.

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Methods used: Total count

• Collect rejects on white filter paper, dry
• vernight at room temperature
• Laminate filter paper
• Scan and analyse by image analysis.

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Methods used: Stickies count

• Collect rejects on white filter paper
• Place blotter on top, press with couch roll

and remove

• Place second blotter on the rejects and

press with couch roll

• Dry both blotters (with rejects) at 110oC for

exactly five minutes

• Use paint brush to remove other materials
• Place transparency film on top of each

blotter

• Scane and analyse by image analysis

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Methods used: Wet specimen

• A black palette with uniform flat surface
• Wet specimen is rolled with a soft roller to

remove the air formed between it and the palette

• A shallow box with a transparent bottom

that is placed on the image analysis glass

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Methods used: Blue dye

• Disintegrate, 1.2 g handsheets
• Couch, discard second wet blotter, replace

by a third one to protect the handsheet

• Dry
• Apply the blue dye to the backside of the

blotter

• Evaporate heptane solvent in the dye
• Peel dyed handsheet, scan, image

analysis

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Methods used: Lamination

• Collect rejects on white filter paper
• Dry
• Place facedown on white copy paper
• Place another copy paper on the filter

paper to make a protective pocket

• Pass twice through a laminator at 125oC
• Staple a transparency film onto the copy

paper with the contaminants

• Scan, image analysis

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Methods used: Transparency film

• Collect rejects onto a white filter paper
• Place wet filter paper, stickies side down,
• n image side transparency
• Place blotter paper on top
• Sandwich filter paper, transparency, and

blotter into paper folder

• Pass sandwiched sheets, twice through

laminator set at 125oC

• Remove blotter and filter paper, allow

transparency to air-dry

• Protect transparency with another

transparency, scan, image analysis

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Methods used: Reference method

• Collect rejects on a white filter paper
• Place another filter paper on top of the

rejects

• Dry by heating and pressing
• Examine each filter paper under a low-

power stereo microscope with aid of a needle

• Manually count contaminants, classify into

– the different classes (stickies, hot melts, plastics, others.)

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Evaluation of the different methods

• To facilitate processing, a DIP sample was

first evaluated using all the methods

• Three most promising ones were then

selected for further testing on the rest of the pulp samples

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Image analysis

• Software: Image-Pro Plus
• Calibrated using image of ruler
• Accuracy checked using calibration plate

(Micro-Scanner, Paprican)

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Image analysis: Micro-Scanner

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Results

• Different scanners

815 ±0.28% 187.32 ±0.07% 834 ±0.52% 283.10 ±2.03% 841 ±0.86% 288.35 ±3.30%

Cleaner rejects

40 ±2.5% 8.98 ±0.28% 47 ±3.20% 13.09 ±1.74% 46 ±5.21% 13.03 ±2.23%

DIP

Number

• f

particles Total surface area, mm2 Number

• f

particles Total surface area, mm2 Number

• f

particles Total surface area, mm2

AGFA scanner HP scanner B HP scanner A

Sample

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Results

0.66 836 831 825 Cleaner rejects 4.5 49 46 45 DIP % error 10 scans 5 scans 1 scan Number of particles 2.6 284.23 277.67 269.62 Cleaner rejects 1.7 13.45 13.012 13.01 DIP 10 scans 5 scans 1 scan % error Total surface area, mm2 Sample

• Reproducibility of scanning measurements

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Results

• Effect of location on the scanner

0.34 842 842 837 Cleaner rejects 4.5 49 46 47 DIP % error bottom middle top Number of particles 2.6 283.37 282.55 284.62 Cleaner rejects 0.39 13.25 13.15 13.18 DIP bottom middle top % error Total surface area, mm2 Sample

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Results

• Reproducibility of the scanning

measurements

– Placement of sample on scanner does not affect the data generated – Scanner generates very reproducible data irrespective of the number of scans

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Results: DIP sample

578 1279 332 108 1684 92 641 579 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 7000 8000 9000

Method 1 Method 2 Method 3 Method 4A Method 4B2 Method 5 Method 6 Method 7 Method 8

Area, mm²/kg

7716 578 1279 332 108 1684 92 641 579 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 7000 8000 9000

Method 1 Method 2 Method 3 Method 4A Method 4B2 Method 5 Method 6 Method 7 Method 8

Area, mm²/kg

7716

3960 11248 1856 111480 976 38472 528 2690 4696 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 55000 60000

Method 1 Voith Method 2 Total Method 3 BTB Method 4A Method 4B2 Method 5 Dye Method 6 Stone Method 7 Aquan-Yuen Method 8 S + HM

# particles per kg

3960 11248 1856 111480 976 38472 528 2690 4696 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 55000 60000

Method 1 Voith Method 2 Total Method 3 BTB Method 4A Method 4B2 Method 5 Dye Method 6 Stone Method 7 Aquan-Yuen Method 8 S + HM

# particles per kg

Number Area

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Results: DIP sample

• Total count

– Measures total # of contaminants – Particles that are not macrostickies also counted

• Wet specimen (4A)

– Gave unrealistic results (25X larger than reference method) – Particles that are not macrostickies also counted

• TAPPI & Transparency methods

– Results very close to reference method

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Results: further testing

0.5 2950 28 567 Reference 18 3528 20 798 Transparency 10 2028 17 401 Stickies count 16 3124 13 992 TAPPI

% error Number % error area Number of particles/kg pulp Total surface area of contaminants, mm2/kg Methods

• DIP sample

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Results: DIP sample

• Significant differences in surface areas of

contaminants

– Reflection of different drying procedures – Methods that require pressure induce deformation

• TAPPI method agrees well with the

reference method in number of particles

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Results: further testing

5 5910 3 273 Reference 14 1136 11 261 Transparency 22 1908 25 246 Stickies count 21 4724 29 1957 TAPPI

% error Number % error area Number of particles/kg pulp Total surface area of contaminants, mm2/kg Methods

• Tissue sample

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Results: tissue sample

• Stickies count and transparency methods

– Best results in agreement with reference method

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Results: further testing

n/a 26,120 n/a n/a

Reference

58 169,097 64 42,954

Transparency

3 843,611 5 271,779

Stickies

15 25,160 12 6,671

TAPPI

% error Number % error area Number of particles/kg pulp Total surface area

• f contaminants,

mm2/kg Methods

• 100% OCC mill

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Results: 100% OCC mill

• TAPPI method gives results similar to

those of the reference method

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Conclusions

• TAPPI method results are comparable to

manual reference method

– Therefore, image analysis using this method is acceptable for rapid measurement of macrostickies

• There is no correct method to measure

areas of contaminants

– Therefore, evaluation of stickies should not be based on area but on number of particles

• Contrast between background and

contaminants is a big problem in image analysis

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Conclusions

• Image analysis does not work well on

highly contaminated samples collected on 100 µ m screens

– Particles hidden under fibres and shives – Best to use 150 µm screen

• If interested in evaluating contaminants,

beside macrostickies, use Table X as a guide to method of choice.

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Thank you for your attention!