Renewable and Biodegradable Monomers for Adhesive Materials

Steve Severtson

University of Minnesota

Pressure Sensitive Adhesives

Release Liner

Inks

Paper Facestock

Pressure Sensitive Adhesive

Research Motivation

Renewable

Resources

Fossil

Fuels

Landfill

Pressure Sensitive Adhesive

Polymers

Sustainable

Life-Cycle

Non-Sustainable

Life-Cycle Unstable

Price &

Availability

$0.00

$0.25

$0.50

$0.75

$1.00

$1.25

$1.50

$1.75

US

Do

llars

(p

er

po

un

d)

Date

Acrylic acid

petroleum derived

materials

materials derived from

biorenewables

“Bridge Technology”

Research Objectives

Modifying existing commercial technologies by incorporating biomass without sacrificing performance or increasing costs.

PSA Market & Composition • Soft Monomers

– Majority of polymer – Allow PSA to flow and wet surfaces – Range: Tg ≤ -40 °C

• Hard Monomers – Provide adhesive and cohesive strength – Range: Tg ≥ 30 °C

• Functional Monomers – Charged groups for stability – Means of crosslinking

PSA Market Share

Tackifier Emulsifier Wetting Agent

Defoamer

Rheology Modifier

Polymer

Composition of Typical Water-Based PSA

$40.6 Billion Total 12.1 Million Tons

Water-based $20.3 Billion

Hotmelt $5.7 Billion

Reactive $6.1 Billion

Solvent $6.5 Billion

Other $2.0 Billion

DPNA International, Inc.

Research Outline • Soft Monomers

– Majority of polymer – Allow PSA to flow and wet surfaces – Range: Tg ≤ -40 °C

• Hard Monomers – Provide adhesive and cohesive strength – Range: Tg ≥ 30 °C

• Functional Monomers – Charged groups for stability – Means of crosslinking

Renewable Resources Tackifier

Emulsifier Wetting Agent

Defoamer

Rheology Modifier

Polymer

Composition of Hybrid Water-Based PSA

2-Ethylhexyl acrylate

n-Butyl acrylate

Copolymerization of Biomass Processing Byproducts with Acrylic Monomers

Molecular Weight ↑ Biodegradability ↓

No Degradation

Degradability of LMW PSA properties of HMW

Bio-Degradation

Ground

Easily degradable “links” Small mass fraction => Small effect on PSA properties

Bio-degradable small chains => Entire polymer is compostable

Enoki, Doi, Iwata. Biomacromol. 2003, 4, 314 Kawai. Appl. Microbiol. Biotechnol. 1993, 39, 382 Haines, Alexander. Appl. Microbiol. 1974, 28, 1084

Weak Link Approach

Adhesive Polymer Containing Acrylated Biomass Macromonomers Copolymer with Conventional Backbone

High Percentage of Biomass Additives from

Renewable Resources

Ground

Additives Degrade

Biomass Degrades

Backbone Remains…

Links in Backbone May Allow for Complete Degradation

Hybrid Pendant Biomass Approach

Petroleum

Renewable Resources

Bio-mass Monomers

Current Monomers

Acrylated Poly(lactic acid)

2-Hydroxyethyl Methacrylate

(HEMA)

Lactide (L)

Macromonomer

(MM)

Hybrid Adhesive Polymer

Generation of Adhesive Polymer Containing Acrylated Macromonomers

Macromonomer Production

Poly(BA-stat-L10C4)

Hybrid Adhesive Polymer

50% Macromonomer

Acrylated Poly(lactic acid)

(HEMA)

(L)

ε-Caprolactone

(C)

MM

Tg (°C)

L6

-26

L8

-20

L12

-8

L10C4

-38

(MM)

Generation of Adhesive Polymer Containing Acrylated Macromonomers

1580 1600 1620 1640 1660 1680 1700

Rel

ati

ve

Inte

nsi

ty

Wavenumber (cm )-1

T = 0 min

C=C

T = 120 min

(a)

0

20

40

60

80

100

0 20 40 60 80 100 120 140

Time (minute)

Co

nv

ersi

on

(%

)

(b)

Polymerization Success Stable Latex

Clear Film

95%

Polymerized

by 1 hour

1"

Shear Test ASTM Test Method

D 6463-99

Loop Tack Test ASTM Test Method

D 6195-03

180° Peel Test ASTM Test Method

D 903-98

500 g

1"

1" 1"

Commercial Adhesive Testing

Three tests used for comparing biomass PSA with commercial PSAs

Shear Test

1"

1,000 g

1"

Loop Tack Test

1"

180° Peel Test

1"

0

1

2

lbs/

in

Commercial Removable PSA Commercial Permanent PSA 50 % (wt/wt) L10C4 MM PSA

0

1

2

3

4

lbs/

in

10

102

103

104

Min

ute

s

Shear Loop Tack 180° Peel

Biomass PSA Comparison

Measuring Biodegradation (BOD)

Pressure Transducer and Needle

Alkali CO2 Trap

Test Sample and Sludge Inoculum

Rubber Stopper

Air Computer

Data Acquisition

Glass Test Jar

CO2

O2

Degradation of Components

-10

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5

BO

D (

mg

/L)

Time (Days)

Buffer Only

Positive Control

Tackifier

Surfactant mix

L10C4

High Percentage of Biomass Tackifying Resins and Surfactants from

Renewable Resources

Ground

Tackifiers Biodegrade

Biomass Biodegrades

Backbone Remains…

Surfactants Biodegrade

Degradation of (Formulated) Biomass PSA

Friberg, T., Progress Paper Recycling, 1996, 6, 70 .

Generation of Contaminants from PSA Products

Research Objective and Approach

Development of new pressure sensitive adhesive (PSA) products that are engineered for enhanced PSA removal during the screening of recycled fiber

Benign Commercial Laminates PSA

PSA

PSA

Commercial Adhesives and Facestock

Database Generation & Analysis

Measurement of Screening Removal Efficiencies

for Laminates

Characterization of Bulk Mechanical and

Surface Properties

Synthesis and Formulation of Model and Commercial Systems

Identification of Key Characteristics for Benign Materials

Testing Removal Efficiencies of PSAs

Valley Flat Screen 15-cut screen

(0.38 mm slots)

PSA 0.5% PSA

Repulping Consistency = 10% 60 Hz (≈ 690 rpm)

Time = 30 min.

TAPPI Method T-205 om-88

Accepts Rejects

Cellulose Dissolution & Resin Oxidation

0.00g 1.23g

Removal Efficiency Quantified

gravimetrically

Removal Efficiency NOT Related to Dry Performance Properties

0

5

10

15

20

25

Pe

el S

tre

ngt

h (

N/2

5m

m)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

0

5

10

15

20

25

Pe

el S

tre

ngt

h (

N/2

5m

m)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

0

2

4

6

8

10

12

14

16

18

20

Loo

p T

ack

(N/2

5m

m)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

0

2

4

6

8

10

12

14

16

18

20

Loo

p T

ack

(N/2

5m

m)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

0

5

10

15

20

25

30

35

40

She

ar (

hr.

)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

Commercial Water -based PSA0

5

10

15

20

25

30

35

40

She

ar (

hr.

)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

Commercial Water -based PSA

0

5

10

15

20

25

30

35

40

Surf

ace

En

erg

y (

mJ/

m2)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

Commercial Water -based PSA0

5

10

15

20

25

30

35

40

Surf

ace

En

erg

y (

mJ/

m2)

0

10

20

30

40

50

60

70

80

90

100

Re

mo

val E

ffic

ien

cy (

%)

Commercial Water -based PSA

0 20 40 60 80 100 120 140

∆L (mm)

0.4

0.3

0.2

0.1

0.0

F (

N)

1”

Temperature

Controlled

Water Bath

PS

A (

1 m

il)

PET

strips

Fmax

Measuring the Strength of Water-Saturated Films

0 5 10 15 20

Soaking Time (min.)

0

0.2

0.4

0.6

0.8

1

1.2 M

axim

um

Ten

sile

Fo

rce

(N)

n-Butyl Acrylate – BA Methyl methacrylate – MMA Methacrylic Acid - MAA 2-Ethylhexyl Acrylate – EHA Vinyl Acetate – VA Acrylic Acid – AA

Poly(BA0.81-co-MMA0.16-co-MAA0.03)

Strengths of Water-based Acrylic PSAs in an Aqueous Environment

Poly(BA0.71-co-EHA0.10-co-MMA0.16-co-AA0.03)

Poly(BA0.71-co-EHA0.10-co-VA0.16-co-AA0.03)

Wet Strength vs. Removal Efficiency

0

10

20

30

40

50

60

70

80

90

100

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Re

mo

val E

ffic

ien

cy (

%)

Wet

Str

en

gth

(N

)

M1 M4 M2 M6 M7 M5 M3 M9 M8

M1 - Poly(BA0.71-co-EHA0.10 -co-VA0.16-co-AA0.03) M4 - Poly(BA0.71-co-EHA0.10 -co-MMA0.03-co-VA0.16) M2 - Poly(BA0.71-co-EHA0.10 -co-VA0.16-co-MAA0.03) M6 - Poly(BA0.71-co-EHA0.10 -co-STY0.16-co-AA0.03) M7 - Poly(BA0.71-co-EHA0.10 -co-MMA0.16-co-AA0.03) M5 - Poly(BA0.71-co-EHA0.10 -co-STY0.16-co-MAA0.03) M3 - Poly(BA0.71-co-EHA0.10 -co-MMA0.16-co-MAA0.03) M9 - Poly(BA0.81-co-MMA0.08 -co-STY0.08-co-MAA0.03) M8 - Poly(BA0.81-co-MMA0.16 - co-MAA0.03)

Model PSA Latexes

Polymerization

Monomers, emulsifiers, other additives, and synthesis

approach

Formulation

Wetting agents, rheology modifiers, defoamers

and tackifiers

Coating

Coating technique and conditions, e.g., direct versus

transfer coating

The extent of film fragmentation during recycling operations is dependent on nearly all aspects of the label adhesive, paper and label production process

Breaking Down the Recycling Compatible PSA Problem

Laminate Design

Paper facestock properties and use of barrier coatings

and filler

Repulping

Wet Strength of Biomass PSA

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

We

t St

ren

gth

(N

)

M1 M4 M2 M6 M7 M5 M3 M9 M8

M1 - Poly(BA0.71-co-EHA0.10 -co-VA0.16-co-AA0.03) M4 - Poly(BA0.71-co-EHA0.10 -co-MMA0.03-co-VA0.16) M2 - Poly(BA0.71-co-EHA0.10 -co-VA0.16-co-MAA0.03) M6 - Poly(BA0.71-co-EHA0.10 -co-STY0.16-co-AA0.03) M7 - Poly(BA0.71-co-EHA0.10 -co-MMA0.16-co-AA0.03) M5 - Poly(BA0.71-co-EHA0.10 -co-STY0.16-co-MAA0.03) M3 - Poly(BA0.71-co-EHA0.10 -co-MMA0.16-co-MAA0.03) M9 - Poly(BA0.81-co-MMA0.08 -co-STY0.08-co-MAA0.03) M8 - Poly(BA0.81-co-MMA0.16 - co-MAA0.03)

B1

Biomass PSA Poly(BA/VA/MM0.5--co-MM0.5)

Challenges to Generating New PSA

Polymer Particle

Monomer Droplet

Conventional

Monomer Biomass

Macromonomer

“Macro” Emulsion Polymerization

Monomer Droplet

Sonicator

Challenges to Generating New PSA Mini-Emulsion Polymerization

Monomer Droplets ~200 nm

Plan Forward Alternative Polymerization

Method (solvent)

Impingement mixing

(mini-emulsion)

Cyclodextrin Multifunctional Additives

Commercialization

90 mass% adhesive polymer 2 - 10 mass% surfactant < 1 mass% everything else

Film composition {

Film formation

latex H H

O

H H

O

H H

O

H H

O

H H

O H H

O

H H

O

release liner

Dry film Emulsion

Fate of surfactant

Compatible Surfactant Phase-separated

Surfactant

Surfactant aggregations

Transport and Fate of Emulsifier

Poly(BA-co-VA-co-MAA)

Sample Preparation and Analysis

4 wt.% SDS in PSA

0

5

10

15

20

25

30

0 5 10

Surf

acta

nt

Co

nce

ntr

atio

n (

%)

Depth (um) #1 PSA #2 PSA #3 PSA

2.75

2.25

1.75

1.25

0.75

0.25

Ta

ck

Fo

rce

(N

/cm

2)

SDS

SDS

SDS

Pure

Latex

Pure

Latex

Pure

Latex

Benefits of Polymerizable Surfactants

Conventional Surfactant

CNPE

Polymerizable Surfactant

PNPE

W/ 4 wt% CNPE W/ No Surfactant (Dialyzed) W/ 4 wt% PNPE

0

1

2

lbs/

in

0

1

2

3

4

lbs/

in

Loop Tack 180° Peel

0

25

50

100

Min

ute

s

Shear

75

Poly(BA-co-VA-co-MAA)

Summary and Future Strategy • New high-biomass content water-based PSAs were synthesized via

substitution of acrylated macromonomers for traditional soft monomers in commercial formulations.

• Reactions via miniemulsion polymerization are rapid and produce stable latexes, and cast films are crystal clear and demonstrate tack, peel and shear performance that meets or exceeds that of most commercial products.

• Furthermore, the films have a high wet strength consistent with high removal efficiencies that are not degraded by factors such as formulation, production and product design.

• Research efforts will include the optimization of the new adhesive and approaches for engineering performance and increasing sustainability.

• However, the main focus, at least initially will be the development of a synthesis approach for generating the PSA at the commercial scale.

Acknowledgements

USDA and DoE

Franklin International

Jiguang Zhang – UMN/Dow

Monique Lander – UMN/EcoLabs

Gang Pu – UMN

Matt Dubay – UMN

Carl Houtman - FPL

Renewable and Biodegradable Monomers for Adhesive Materials

Steve Severtson

University of Minnesota