Degradable cigarette filters: Evaluating TiO2 additives

Steven A. Wilson & Jeremy Steach Eastman Chemical Company

TSRC 2013

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Objectives

Current work: Evaluate titanium dioxide (TiO2) additives for photo activity

Long term: Evaluate ways to enhance the degradability of filter materials Facilitate the reduction of cigarette filter litter

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Environmental factors • Biological activity • Sunlight • Rain • Wind • Physical abrasion

Potential solutions • Enhanced biodegradation • Enhanced photo degradation • Disintegration

Factors impacting cigarette filter litter

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Background on filters

Filter composition • Cellulose acetate (CA) fibers • Triacetin • Papers • Adhesives

CA polymer without TiO2 has limited photo degradability CA fibers are biodegradable CA fibers typically contain TiO2 as a whitening agent

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Properties of TiO2 additives

Crystal types - anatase or rutile Particle size - whitening occurs with pigment size particle (~200

nm) Inorganic coating – silica or alumina to enhance dispersion, can

deactivate photo activity BET surface area – 10 to 20 m2/g

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History of photoactive TiO2 research TiO2’s photo catalytic properties were discovered in 1967 Uncoated anatase is more photo active than uncoated rutile

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Evaluation of photoactive TiO2

Degradable cigarette filters

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Evaluation of TiO2 particles for photo activity

Conducted an extensive screening of TiO2’s for photo activity Tow samples created in Eastman’s pilot plant

• 0% TiO2

• 0.5% coated anatase pigment-sized TiO2

• 0.5% uncoated mixed-phase ultrafine TiO2 (photo active)

Tow converted to filter samples with triacetin Filters tested outdoors without plugwrap

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Comparing TiO2 particles

Sample TiO2 Level Primary Particle

Size*

BET Surface Area*

Anatase Rutile

No TiO2

0 %

-

-

-

-

Coated Anatase

0.5 %

200 nm

20 m2/g

100 %

0 %

Uncoated Mixed

Phase**

0.5 %

20 nm

65 m2/g

87 %

13 %

* TiO2 product specifications information

** US 2012/0325233 - “Cellulose esters having mixed-phase titanium dioxide particles for improved degradation”, Wilson, Steach, & Fauver

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Outdoor weathering – experimental details

Stainless steel cages were placed on top of bricks 10 filter tips per sample area Periodically measured weights Samples were equilibrated for 48 hours in the lab, which was set

at 70˚F and 60% humidity prior to weighing

2012 Coresta paper: Photo degradability testing of cellulose acetate filters – outdoor weathering vs. accelerated weathering, J. K. Steach & D. Fisher Jones

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Outdoor weathering – set up

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Rooftop weathering: filter tip comparison of TiO2 types

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8 9 10

Rem

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Time, Months

0% TiO2

0.5% Coated anatase pigment size TiO2

0.5% Uncoated mixed-phase ultrafine TiO2

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Rooftop results: SEM images of fibers

0% TiO2

0.5% coated anatase pigment size TiO2

0.5% Uncoated mixed phase ultrafine TiO2

Not Weathered

Note: good Y cross sections

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Rooftop results: SEM images of fibers

Weathered for 3 months

0% TiO2

0.5% coated anatase pigment size TiO2

0.5% Uncoated mixed phase ultrafine TiO2

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Rooftop results: SEM images

0 Months

3 Months

0% TiO2

0.5% coated anatase

pigment size TiO2

0.5% Uncoated mixed phase ultrafine TiO2

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Rooftop weathering: filter tip comparison of TiO2 types

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8 9 10

Rem

aini

ng w

eigh

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Time, Months

0% TiO2

0.5% Coated anatase pigment size TiO2

0.5% Uncoated mixed-phase ultrafine TiO2

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Filter properties for cellulose acetate tow with 0.5% uncoated mixed-phase ultrafine TiO2

Good tow whiteness perceived Equivalent plugmaker processing capability Equivalent smoke filtration results

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Potential degradation mechanism combinations

Enhanced disintegratable designs • Partial cut - US Pat. 5,947,126 & 7,435,208 • ROA filters - US Pat. 3,658,626

Enhanced biodegradation designs

• Low acetyl CA fibers - US Pat. 5,512,230 & 6,133,439 • Enhanced biodegradation additives

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Cellulose acetate degradability references

Degradation of Cellulose Acetate-Based Materials: A Review, Journal of Polymers and the Environment, 2011, Vol. 19, pp. 152-165 Aerobic Biodegradation of Cellulose Acetate, Journal of Applied

Polymer Science, 1993, Vol. 47, pp. 1709-1719 Biodegradation of Radiolabeled Cellulose Acetate and Cellulose

Propionate, Journal of Applied Polymer Science, 1993, Vol. 50, pp. 1739-1746 Compostability of Cellulose Acetate Films, Journal of Applied

Polymer Science, 1994, Vol. 52, pp. 1477-1488

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Conclusion

Degradable cigarette filters

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Conclusion

Enhanced photo degradability of cellulose acetate tow can be achieved with the addition of uncoated mixed-phase ultrafine TiO2 particles Degradation times can be reduced from a few years to a few

months in the outdoor environment using photoactive TiO2 particles

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Thank you!

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