Macro Stickies and Screening - · PDF file · 2009-06-06Macro Stickies and Screening ... PSA Particle Screening ... Decreases Screening Efficiency Pressure Screening 10 100 1,000

Macro Stickies and Screening

Background

Research Objective

Results and Discussion

PSA Particle Screening

PSA Particle Breakage

PSA Particle Extrusion

Overall Conclusions

Future Research

Pressure Sensitive Adhesives

Pressure sensitive adhesive base polymers consist of acrylic or rubber-based polymers

Glass transition temperature is below room temperature and depends on the adhesive formulation

Young’s modulus and shear strength are low and depend on the adhesive formulation and the system temperature

Pressure Screening

Pressure screening is

considered to be the most

effective way to remove

adhesive contaminants from

pulp

Typical removal efficiencies

of adhesive contaminants

range from 50 to 80% for

commercial pressure screens

Analysis of Stickies -- SOWM. A. Pikulin, AF&PA and USPS Joint Conference to

Address PSA Issues, June 1996

0

5

10

15

20

25P

ulp

er

'Scre

en

"S

cre

en

Flo

tn.

Pro

du

ct

Styrene-Acrylate

SBR

PVAC,EVA

Acrylate

SIS Copolymer

Particle Breakage

Breakage of PSA particles depends on the:

Shear/tensile strength of the PSA

Shear/tensile forces in the device

If the forces in the device are greater than

the strength of the PSA material, then the

PSA material will break

Research on Screening of Stickies

Studies of the effects of operating parameters and

equipment on removal efficiency by: Consistency, slot velocity, and slot width [Vitori, Pulp and Paper

Canada, 1993]

Reject rate, rotor speed, and slot velocity [Heise, Tappi Journal,

1992]

Consistency, reject rate, rotor speed, slot velocity, and slot width

[Seifert, et. al., 5th Research Forum on Recycling, 1999]

Consistency, rotor speed, slot velocity, and slot width [Saint Amand

and Perrin, Tappi 1998 Pulping Conference, 1998]

Results from Previous Research

Removal efficiency increased to a maximum at an optimum consistency

Removal efficiency increased as the:

Reject rate increased

Rotor speed, slot velocity, or slot width decreased

Weaknesses in the studies were:

Undefined materials

Relationships between efficiency and operating conditions were defined but not explained

Little insight provided on the mechanism of passage

Outline

Background

Research Objective





Overall Conclusions

Future Research

Research Objective

To understand how the operating

conditions and adhesive formulation

affect the passage of pressure sensitive

adhesive particles in industrial and

laboratory screens

Outline

Background

Research Objective





Overall Conclusions

Future Research


Do pressure sensitive adhesive particles

behave differently in industrial pressure

screens than in laboratory screens?

Approach: Study the removal of pressure

sensitive adhesive particles by an industrial

pressure screen and laboratory screens

Pilot Plant Layout

Rejects

Flow

Meter

Pump

Industrial

Screen

Feed

Stock

Tank

Second

Stock

Tank

Accepts

Shower

Screening Parameters:

1% Consistency, 50oC,

0.006 in. wide slots,

Mass Reject Ratios of

4.5%, 12%, 15%, and 25%

Lab scale screening

Valley Flat Screen

0.006 in. slots

25oC, 45oC

Pulmac

MasterScreen

0.006 in. slots

25oC

Accepts

Accepts

Rejects

Rejects

Pilot Plant

Pulper

Samples

Detection of Stickies

Handsheet

Morplas Blue - Heptane Dye Solution

Dyed

Handsheet

for Image

Analysis

Cleanliness Efficiency of

Industrial and Laboratory Screens

0

20

40

60

80

100In

du

stri

al,

RR

=4

.5%

Ind

ust

rial,

RR

=1

2%

Ind

ust

rial,

RR

=1

5%

Ind

ust

rial,

RR

=2

5%

Pu

lmac,

25

C

Vall

ey

,

25

C

Vall

ey

,

45

C

Screening Devices

Cle

an

lin

ess

Eff

icie

ncy

, %


Do pressure sensitive adhesive particles behave differently in industrial pressure screens than in laboratory screens?

Yes, pressure sensitive adhesive particles behave differently in industrial pressure screens (40-70% efficiency) than in laboratory screens (99% efficiency).

Outline

Background

Research Objective





Overall Conclusions

Future Research


Do PSA particles breakdown in the industrial pressure screen?

Approach: Analyze the PSA particles before and after the industrial pressure screen

Intense Forces in a Industrial Slotted Pressure Screen

Break/Deform Adhesives: Decreases Screening Efficiency

Pressure

Screening

10

100

1,000

10,000

<0.50 0.50-

1.00

1.00-

1.50

1.50-

2.00

2.00-

2.50

2.50-

3.00

>3.00

Particle Size, mm2

Pa

rti

cle

s i

n 1

m2

Feed

Accepts +Rejects

“Thousands of small

particles generated”

Shredding

makes

particles more

1-dimensional

Screen Removal Efficiency

Versus Particle Size

-1500

-1300

-1100

-900

-700

-500

-300

-100

100

<0.50 0.50-

1.00

1.00-

1.50

1.50-

2.00

2.00-

2.50

2.50-

3.00

>3.00

Particle Size Ranges, mm2

Reje

ct

Eff

icie

ncy,

%

RR=4.5%

RR=10%

RR=15%

RR=25%


Do PSA particles breakdown in the

industrial pressure screen?

Yes, PSA particles do breakdown in the

industrial pressure screen.


Which operating parameters in an industrial

pressure screen have the most significant effect

on the breakage of PSA particles?

Approach: Conduct a statistical analysis

experiment using a high intensity laboratory mixer

simulating forces in a screen with PSA particles

Experimental Procedure

Pilot Plant Pulper

10% K, 45oC, 20 min

80 OD lbs.

Copy Paper with

Adhesive Labels

(1% by wt.)

Samples

Quantum

High Shear Mixer

3 Liters

(vary parameters)

Handsheets

Dyeing

Image Analysis

Operating Parameters

Full Factorial Design Experiment with a

Center Point

Variable Low Value Center Point High Value

Pulp Consistency,% 3 7.5 12

Mixing Time, seconds 30 165 300

Initial Temperature, oC 20 35 50

Rotor Speed, rpm 600 1500 2400

0

300

600

900

1200

1500

1800

2100

CO

NS

TIM

E

TE

MP

RO

TO

R

CO

NS

TIM

E

CO

NS

TE

MP

CO

NS

RO

TO

R

TIM

ET

EM

P

TIM

ER

OT

OR

TE

MP

RO

TO

R

CO

TIT

E

CO

TIR

O

CO

TE

RO

TIT

ER

O

CO

TIT

ER

O

Variable

|Eff

ect|

2 Limit

Pareto Analysis: Number of PSA Particles

Versus Operating Variables

Number of Particles in 1 m2

vs. Consistency

0

4000

8000

12000

16000

0 4 8 12 16

Consistency, %

Nu

mber

of

Par

ticl

es in

1 m

2

Treated

Untreated

Number of Particles in 1 m2

vs. Initial Temperature

0

2000

4000

6000

8000

10000

12000

0 20 40 60 80

Initial Temperature, oC

Nu

mber

of

Par

ticl

es in

1 m

2

Treated

Untreated

Average Particle Size

vs. Time

0.00

0.20

0.40

0.60

0.80

1.00

0 60 120 180 240 300 360 420

Time, seconds

Aver

age

Par

ticl

e S

ize,

mm

2

Treated

Untreated


Which operating parameters in an industrial pressure screen have the most significant effect on the breakage of PSA particles?

The operating parameters of consistency, time, and temperature have the most significant effect on the breakage of PSA particles.


How do the pressure difference across the

slot and operating temperature affect

particle passage through a slot?

Approach: Measure the pressure difference

at which PSA particles pass through the slot

of a pressurized single slot device at

different temperatures


450H Pulper

12% K, 45oC,

415 rpm, 60 min

450 OD g of paper

10 adhesive labels

Single Slot Device

0.18 mm wide slot

Single Slot Device Procedure

Remove a PSA particle from pulp

Measure the dimensions of the PSA particle under a microscope

Place the PSA particle on the slot

Add 1000 mL of deionized water

Slowly open the vacuum line valve to increase the pressure difference across the slot

If the particle passes through the slot, record the vacuum pressure at which the particle passes through the slot

Top View

Side View

PIV

a

c

u

u

m

Commonly Observed

Particle Passage Process

Increasing Pressure Difference

indicates

Cumulative Particle Passage

Versus Pressure Difference

0

20

40

60

80

100

0 20 40 60 80

Pressure Difference, kPa

Cu

mu

lati

ve

Par

ticl

e P

assa

ge,

%

5C

20C

50C

Typical Pressure Differences in an

Industrial Pressure Screen*

*Bliss, T., and Ostoja-Starzewski, M., 1997 Tappi Korea Recycling Symposium, pp. 1-17, 1997.


How do the pressure difference across the

slot and operating temperature affect particle

passage through a slot?

Increasing the pressure difference across

the slot or the operating temperature

increases particle passage through a slot.


Do the mechanical properties of the PSA formulations affect the passage of PSA particles through a slot?

Approach: Analyze particle passage in the

single slot device for PSA films with

different formulations


450H Pulper

12% K, 45oC,

415 rpm, 30 min

450 OD g of paper

6 adhesive labels

Single Slot Device

0.18 mm wide slot

Particle Passage Versus Particle Area for

Eight Different Formulations

0

20

40

60

80

100

0.0 1.0 2.0 3.0 4.0

Calculated Particle Area, mm2

Cum

ulat

ive

Par

ticl

e P

assa

ge, % BA BA:A

BA:G BA-EA

BA-EA:A BA-EA:G

AC SIS

Calculated (Yield Stress and Area)

Versus Actual Particle Passage

0

20

40

60

80

100

0 20 40 60 80 100

Actual Particle Passage, %

Cal

cula

ted

Par

ticl

e P

assa

ge,

%


Do the mechanical properties of the PSA formulations affect the passage of PSA particles through a slot?

Answer: yes, yield strength and size are

the most critical properties

Overall Conclusions

PSA particles break down in industrial

pressure screens

Consistency, temp and time affect breakage

PSA particles extrude in industrial pressure

screens

Pressure drop, temp, and particle size and

stiffness affect passage

Macro Stickies and Screening - · PDF file · 2009-06-06Macro Stickies and Screening ... PSA Particle Screening ... Decreases Screening Efficiency Pressure Screening 10 100 1,000

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