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Additives for polyolefins: chemistryinvolved and innovative effects
Mara DestroIntelligent packaging; session number7733
Mara DestroSession number 7733
Outline of Presentation
Weatherability of HALS in LLDPE Film and Impact of PPA on the Performance of HALS Oxygen Scavengers in Packaging Applications
Mara DestroSession number 7733
Part I
Weatherability of HALS in LLDPE Film and Impact of Polymer Processing Aids
on the Performance of HALS
Mara DestroSession number 7733
Polymer Processing Additives (PPA)
Eliminate Melt Fracture
Reduce Operating Pressure
Alleviate Die Build- Up
Reduction in Gel Formation
Typically Fluoroelastomers or Mixture with PEG
Mara DestroSession number 7733
Hindered Amine Light Stabilizer (HALS)Widely used for outdoor applicationsFree radical scavengersEffective in high surface area applications (Films)However, HALS have been documented to have interactions with PPAIs it possible to use HALS and PPA together without having negative interactions?A continuation of the previous workThe HALS in this study: more according to current recommendations
Mara DestroSession number 7733
R* H
ROO·R=O + ROH
R·
[Oxidation]
R
NO R
NO·
RR
NR*
[H+]
R
N+
XNOTE: An acidified hindered amine cannot easily enter into the free radical scavenging cycle
R* = - H- CH3
N-H and N-R Hindered Amine Stabilizers (HALS) fit most needs regarding light stability, but can be alkaline (basic)
N-OR type HALS enter the UV stabilization cycle quickly, and are not alkaline, in comparison to N-H & N-R type HAS
Hindered AminesUV Stabilization via Free Radical Scavenging
Mara DestroSession number 7733
Bring Out Your Magic DeCoder Rings
• HALS-1 = Tinuvin 622 (N-R)• HALS-2 = Chimassorb 119 (N-CH3)• HALS-3 = Chimassorb 944 (N-H)• HALS-4 = Tinuvin NOR 116 (N-OR)• HALS-5 = Chimassorb 2020 (N-H)• HALS-6 = Tinuvin 783: HALS -1 + HALS-3 (N-R + NH)• HALS-7 = Tinuvin 111: HALS -1 + HALS-2 (N-R +N-CH3)• HALS-8 = Tinuvin NOR 371 (N-OR)
• PPA = Dynamar FX-5920A
Mara DestroSession number 7733
Structures of Various Hindered Amines
N
N
N
N
NNN
N
H
H H
(CH2)6
n
N
N N
N
N
N
NN
R R
H
R
R ]2-
NN CH3
C4H9
R =
N
O
OO
O
n
HALS-3
HALS-5
HALS-4HALS-1
HALS-2
N
N
N
NN
NN
OO
R =
C4H9C4H9
NHN NH
N
R R
H R
NN
NN
N
NH
N N
N
N
NH
N
NH
N NH
NN
N
N
N
H
NN N
n
Mara DestroSession number 7733
0 2 4 6 8 10
pKa (as measured by titration of Conjugate Acid)
HALS-3 (N-H)
HALS-5 (N-H)
HALS-2 (N-CH3)
HALS-1 (N-R)
HALS-4 (N-OR)
HALS-8 (N-OR)
Dominant pKa's of Various Hindered Amines (Piperidinyl Group)
Alkalinity of Various Hindered Amines
Mara DestroSession number 7733
Experimental Procedures
Made 90 µ blown film samples using zn-LLDPE
Films contains HALS 1, 3, 6, 7, 8 @1500 and 3000ppm
One series with no PPA and the other with PPA
Xenon weathering per ASTM G155 to 8,000 hours
Mechanical properties
Color measurement after gas fade and oven aging
Mara DestroSession number 7733
Performance of HALSXenon Weathering of zn-LLDPE (w/ 1500 ppm HALS, No PPA)
0
25
50
75
100
125
0 2000 4000 6000 8000Hours in Xenon Weatherometer
% R
etai
ned
Elon
gatio
n
none
HA-3 (N-H)
HA-1 (N-R)
HA-6 (NR+NH)
HA-7 (NR+NCH3)
HA-8 (N-OR)
Mara DestroSession number 7733
Influence of PPA on HALSXenon Weathering of zn-LLDPE (w/ 1500 ppm HALS; 900 ppm PPA)
0
25
50
75
100
125
0 2000 4000 6000 8000Hours in Xenon weatherometer
% R
etai
ned
Elo
ngat
ion
none
HA-3 (N-H)
HA-1 (N-R)
HA-6 (NR+NH)
HA-7 (NR+NCH3)
HA-8 (N-OR)
Mara DestroSession number 7733
Gas Fade Discoloration with PPAGas Fade Aging of zn-LLDPE: (w/1500 ppm HALS; 900 ppm PPA)
0
5
10
15
0 5 10 15 20 25 30Day in Gas Fade Chamber at 60°C
YI C
olor
none
HA-3 (N-H)
HA-1 (N-R)
HA-6 (NR+NH)
HA-7 (NR+NCH3)
HA-8 (N-OR)
Mara DestroSession number 7733
Summary of Weatherometer Work• Ranking of HALS Performance in Weatherometer (no
PPA)– Good:
• HALS-1 (N-R)• HALS-3 (N-H)• HALS-7 (NR + N-CH3) ≤ HALS-6 (NR + N-H) ≤ HALS-8 (N-OR)
– Best
• Ranking of HALS Performance with PPA:– Good:
• HALS-1 (N-R)• HALS-7 (NR + N-CH3) ≤ HALS-6 (NR + N-H) ≤ HALS-3 (N-H)• HALS-8 (N-OR)
– Best
Mara DestroSession number 7733
ConclusionHMW NOR Hindered Amines and Hindered
Amine blends are more effective in outdoor film applications than the individual HALS
Slight impact of the PPA on the effectiveness of the HALS
PPA have slight negative impact (15-20% reduction in physical properties): HALS-1, HALS-6, and HALS-7
PPA has no impact: HALS-3PPA has slight positive impact: HALS-8
It is possible to use HALS and PPA together without having negative interaction (selectively)
Mara DestroSession number 7733
16
Part IIOxygen Scavenging Technologies for Food Packaging Applications
• Review of Oxygen Scavenger Technology
• Design Consideration in Packaging Applications• SPO2 Oxygen Scavenger• Retort Example using EVOH/SPO2
Mara DestroSession number 7733
17
Oxygen: The Spoiler
• Residual oxygen within package & oxygen entering package throughout storage leads to product deterioration
– Discoloration– Nutrient Loss– Off-Flavor – Texture Changes– Oxidative Rancidity
Mara DestroSession number 7733
18
Enhancing Barrier Properties• Traditional Means of Oxygen Exclusion
– Metal & Glass Packaging– Barrier Plastic Packaging, Potentially Combine with
• Gas Flushing• Vacuum Packaging
• Still Enough Residual Oxygen to Cause Problems
• Potential Solution: Scavenging Technologies in Combination with Barrier Packaging– Scavengers Chemically Bind Oxygen
Mara DestroSession number 7733
19
Oxygen Scavenging Chemistries
• Metal Based Systems– Fe + 3/4 O2 + 3/2 H2O ---- Fe(OH)3– Moisture activated
• Oxidizable Polymers– Unsaturated hydrocarbon such as polybutadiene– Polyamides, MXD6– Photoinitiator / UV activated
• Low MWt Organic / Inorganic Compounds– Ascorbic acid derivatives– Sulfites– Reduced anthraquinone/ benzophenone derivatives
Mara DestroSession number 7733
20
Package Design Considerations
• Determine Amount of Oxygen to Scavenge– Initially Present in Package
• Headspace Volume• Dissolved Oxygen in Product
– Oxygen Ingress over Time• Permeation Rate (Barrier)• Package Dimensions• Shelf-life (time)
• Role of Scavenger– Head Space Oxygen Removal
– Barrier Enhancement
Mara DestroSession number 7733
21
Package Design Considerations
• Scavenger Characteristics – Oxygen Absorption Capacity
– Scavenger Rate
– Loading Limitations
– Location of Scavenger within Package Structure
• Any barrier layer between scavenger and food?
Mara DestroSession number 7733
SPO2 Oxygen Absorber• SPO2: Scavenger Product for Oxygen (O2)
– Iron-based– Formulated oxygen scavenging systems– Polyethylene & polypropylene carrier resin– Incorporated in multilayer structure by coextrusion– Activated by water: RH ≥ 70% – Thermally stable up to 250°C
23
Effect of Relative Humidity on SPO2 Absorption
0%
20%
40%
60%
80%
100%
0 20 30 40 50 60 75 100Relative Humidity (%)
SPO
2O
xyge
n A
bsor
ptio
n C
apac
ity
Mara DestroSession number 7733
Retort Applications: SPO2 / EVOH• Retort: Steam sealed food @ 251-270F for up to 30 min.• PP/EVOH barrier widely used• EVOH Barrier: Very sensitive to humidity• “Retort Shock”—Reduction of EVOH barrier due to
humidity increase in retort process• SPO2 + EVOH: Complementary effects
– Higher Moisture: SPO2 most effective when EVOH loses barrier– Low Moisture: EVOH most effective when SPO2 less effective
Mara DestroSession number 7733
26
Barrier PerformanceBarrier behavior after retort
100% O2, 65%RH out - 100%RH in
0.0000
0.0100
0.0200
0.0300
0.0400
0.0500
0.0600
0.0700
0.0800
0 10 20 30 40 50 60 70Days
O2T
R (c
c/pa
ckag
e.da
y.at
m) Packaging with no SPO2 no retort - theoretically
Packaging with SPO2 after retort - measured
Packaging with no SPO2 after retort - theoretically
Mara DestroSession number 7733
Conclusion
Review of oxygen scavenger technologies
Oxygen scavenger can be a value tool in meeting some toughest packaging applications
Combination of passive barrier and oxygen scavenger can lead to improved barrier performance
SPO2 / EVOH combination can lead to optimum synergic barrier performance in retort application
Mara DestroSession number 7733
Acknowledgments
Ciba Specialty Chemicals– Joanni Turnier, Scott Allen, Marie-Raphael Morvillier, Joe Agocs,
Jiong Yu, Peter Solera and Florian Stricker
Thank you for your attentions!
Mara DestroSession number 7733
Gas Fading
OH OH
O
NO2 NO2
NO2
O
-HONO
O
OH
OH
-HONONO2
O
O
OH
NO2
O
NO2
2RO.-2ROH
O
N+
O
OOH-
H+
slightly yellow strong yellow
vis-absorption106’000 [l*mol-1cm-1]
Mara DestroSession number 7733
Typical Structure of Polymer Processing Aid
F
F H
H
CF3
F
F
Fnm
C C CC
δ−
δ− δ−
δ−δ+
δ+
Mara DestroSession number 7733
Summary of Previous Work• Ranking of HALS Performance in Weatherometer
– Good:• HALS-1 (N-R)• HALS-2 (N-CH3) • HALS-3 (N-H) ≤ HALS-5 (N-H) ≤ HALS-4 (N-OR)
– Best
• Ranking of Interaction of HALS with PPA:– Most interaction:
• HALS-3 (N-H) • HALS-5 (N-H) ≤ HALS-4 (N-OR) ≤ HALS-2 (N-CH3) • HALS-1 (N-R)
– Least Interaction
Mara DestroSession number 7733
33
Oxygen Scavenger Technology• Under Development for 30+ years• Recent Trends Contributing to Interest in Oxygen
Scavenger Technology– Convenience Packaging – Increased Plastic Usage– Shelf Stable – No Need for Refrigeration– Demand for Improved Quality
• Taste• Texture• Appearance
– Tailoring Package Environment for Product Needs
Mara DestroSession number 7733
Oxygen Scavenging Sachets• Strengths
– Established Market Presence– Large Absorption Capacity – Baseline for Price/Performance Evaluations – Many Options
• Challenges – Processing Speed
• Reduced Linespeeds for Sachet Insertion• Concerns about 100% Placement of Sachet
– Foreign Object Presence in Package – Does not work with Liquid Products
Mara DestroSession number 7733
35
In Package Systems
• Oxygen Scavenger Incorporated in Multilayer Structure
• Strengths– Eliminate “Foreign” Object in Package
– Can use Normal Packaging Process Conditions
– Can be Used with Wider Range of Products – i.e. Liquids
• Challenges– Meeting Rate/Capacity Application Needs
– Impact on Package Attributes
Mara DestroSession number 7733
SPO2 Structures/Uses
• Use in Combination with Barrier Packaging • Rigid Containers• Lids of Rigid Containers• Bottles • Films• Closure Liners