1. Dr. Mick Jakupca Jake Lance Dover Chemical Corporation
Investigating the use of polymeric phosphites to improve processing, melt fracture and thermal stability
Dr. Mick Jakupca
Jake Lance
Dover Chemical Corporation
2019 SPE Polyolefins Conference
Houston, Texas

2. Presentation Outline
Introduction to non-alkylphenol based polymeric phosphite stabilizers (Doverphos LGP-11)
LGP-11 performance data displaying the typical functions of a phosphite
LGP-11 ancillary benefits that are not typical of commodity phosphites
And…an unexpected benefit…how to use polymeric phosphites as melt fracture synergists

3. Phosphite Stabilizers
What it is a phosphite supposed to do?
Protect the polymer from degrading during melt processing
Get “out of the way” when it is done
Do not negatively affect other properties such as color, NOx gas fade, gamma irradiation, compatibility, plate-out and bloom, migration and exposure, etc.

4. Polyolefin Stabilizers
Most polyolefin stabilizer packages include a primary antioxidant (such as a hindered phenolic) and a secondary antioxidant (usually a phosphite). This is what phosphites are “supposed to do”.

5. What They Are “Not” Supposed To Do…
Do not add significant color either during processing or heat aging
Do not plate-out on equipment during processing, especially in LLDPE cast film application
Do not bloom to the surface of the polymer post-processing
Do not hydrolyze (can cause bad specs and poor stability)
Do not negatively interact with other additives such as PPAs, UV stabilizers, etc.
Do not significantly migrate from polymers to food (migration is proportional to molecular weight)

6. What They Are “Not” Supposed To Do…
Do not contain components that are present on various regulatory lists such as Prop 65, nor are considered Substances of Very High Concern (SVHCs).
Do not contain components that are present on non-regulatory NGO “hit lists” Often emotional issues, not safety, but just as important if you want to sell your product and “keep it alive” for the long term.
Preferably do not contain alkylphenols which are often present on both types of lists.
Do not result in Non-Intentionally Added Substances (NIAS) during processing or post processing (now a major focus….even at ppm levels).

7. Doverphos LGP-11 – Polymeric Phosphite
Doverphos LGP-11 is a polymeric phosphite that was designed to be “Green”. Very low migration/exposure, good performance and composed of materials that are not based on alkylphenols or other components “under the spotlight”
Most of the commonly used melt process stabilizers are based on alkylphenols
TNPP
SP-1
DN76

8. What Phosphites Are “Supposed To Do”
Phosphites are used with primary antioxidants to protect the polymer during melt processing
Multiple pass extrusion tests are a common method of measuring melt stability of the polymer (melt index and color)
LLDPE Resin (Metallocene)
800ppm of phosphites (LGP-11 vs. SP-1)
500ppm of primary AO-1
Co-rotating twin screw extruder
Compounding: °C
Multi-pass: °C

9. Melt Index (MI) (2.16kg/190°C)
LGP-11 and SP-1 Have Similar Performance
And Similar % Phosphorus

10. Yellowness Index (YI) LGP-11 has MUCH better color control than SP-1
(It is a fast phosphite, alkyl versus alkylphenol)

11. Expectations
LGP-11 does what it is supposed to do during melt processing
Good MI performance compared to SP-1 (and TNPP)
Excellent YI control compared to commodity phosphites
What happens after melt processing? Does it do anything it is not supposed to do? (The advantages of LGP11 have been covered in previous presentations)
Compatibility and bloom/exudation
Gamma Irradiation
Migration and exposure
Etc.
BUT…..what else is there? This paper will focus on unique processing benefits offer by polymeric phosphites

12. Plate-Out/Bloom
Phosphites can contribute to plate-out and bloom issues causing buildup on production equipment and powder/haze on surface post production.
White film on surface indicates additive is blooming
Film is clear

13. Compatibility-Bloom Test
Compound LLDPE formulation in Brabender-Bowl (torque rheometer) followed by compression molding and quench cooling. This results in highly amorphous LLDPE.
Aging the compression molded plaques at 60°C accentuates any potential of the additives to bloom.
Bloom can be monitored by measuring the surface gloss. Surface gloss is reduced if an additive blooms. The composition of the bloom can be identified by surface ATR-FTIR and other analytical techniques

14. Bloom Measurement Phosphites loaded at 2000ppm LGP-11 vs SP-1 vs TNPP
The solid phosphite SP-1 is known to have compatibility issues when used in cast film applications at levels >1000ppm. It can plate-out on equipment during processing, leading to shut-downs and cleaning. It can cause surface bloom/powder to form after processing.
TNPP is generally preferred over SP-1 in cast film applications because of its good compatibility

15. Compatibility @ 2000ppm in LLDPE
Solid phosphite SP-1 is not compatible at 1500ppm

16. LGP-11 Can Be Used to “Help Out” SP-1
Blend of LGP-11 and SP-1
Solid phosphite SP-1 is not compatible at 1500ppm

17. Improved NOx – Gas Fading Performance
Hindered phenolic antioxidants are a major contributor to color increase during NOx exposure and heat aging. High loading levels and over-oxidation of the phenolic AO cause increased discoloration.
LGP11 is a “Quick” phosphite. Kinetic studies have shown that it quickly scavenges hydroperoxides, and thus doesn’t make the primary AO work “as hard”. (Helps prevent formation of color causing quinone species).

18. Another Option – LGP11 and Vitamin E
Vitamin E is a “fast” primary AO, it is a carbon radical scavenger. Its main drawback is higher color.
LGP11 is a “fast” phosphite, and eliminates the color issue associated with Vitamin E when used as a blend. A “fast” phosphite plus a “fast” primary antioxidant.
Blends of LGP11 and Vitamin E can significantly reduce or eliminate NOx gas fade color issues
Replacement or reduction of hindered phenolic AO with much lower loading levels of Vitamin E
LGP11 improves initial color, protects the Vitamin E from over-oxidation and results in little color increase upon aging

19. Improved Gas Fading Performance
Comparison between TNPP/DN76 versus LGP11/DN76 and LGP11/Vitamin E
1500ppm TNPP and 500ppm DN76
1500ppm LGP11 and 500ppm DN76
1500ppm LGP11 and 100ppm Vitamin E
LLDPE Formulations extruded three passes at 250°C
Samples of the 3rd pass were compression molded into 20mil thick plaques and aged in a NOx chamber at 50°C
Yellowness Index (YI) was measured during the exposure

20. Gas Fading/NOx Performance

21. Migration- Food Packaging
In food packaging applications, additives will migrate from the polymer into the food. The amount of migration is related to the moleculare weight of the additive.
NIAS (Non Intentionally Added Substance) is currently a major concern. Attention is being focused not only on the additives themselves, but also their oxidation and hydrolysis products.
LGP-11 is polymeric which limits migration. It is also well known that chemicals with a molecular weight great than 1,000 are not readily bioavailable, and thus less of a toxicity concern.

22. Migration - Fickian Diffusion
At a given time/temperature/concentration, migration is related to the diffusion coefficient, which is dependent upon Molecular Weight
Mt = 2Cpo(Dpt/π)1/2 *
Mt = Migration at time t
Cpo = Concentration in the polymer
Dp = Polymer diffusion coefficient
Dp = 104 exp(Ap–aMw– bT-1) **
Dp is the diffusion coefficient of additive/migrant
Mw is the molecular weight of the additive, Diffusion will exponentially reduce as MW goes up
T is temperature (K)
a and b are constants (0.01 and respectively)
Ap depends on the polymer and temperature
Molecular Weight
* Crank, J., “The Mathematics of Diffusion”, 2nd ed., Oxford University Press, London, 175
** A.Baner, J.Brandisch, R.Franz, O.G. Piringer, Food Additives and Contaminants, 1996, 13(5),

23. FDA-Type Migration Study of Additives Into Food
Selected additives were compounded into LLDPE using a Brabender torque rheometer at a concentration of 1000ppm. Formulations were then compression molded into plaques.
Plaques were exposed to 95% ethanol at 70°C for 2 hours. 95% ethanol is considered a fatty food simulant. Solutions were then analyzed for additive content.
Additive migration was measured as µg of additive that migrated per inch squared surface.
ppm in
Food
µg (additive)
in2 surface
Assume
10g food/in2
(µg (additive)/10)
grams food

24. Migration of Additives - Fatty Food Simulant
MW (g/mole)
Ppm in Food
DTBP
206
15.2
SP-1
646
5.2
TNPP
688
5.9
SP-2
852
2.2
LGP-11
>1500
<0.5

25. Migration and Molecular Weight
Amount of migration decreases with MW
At a set time and temperature, relationship is not linear
Migration exponentially decreases with an increase in MW
Dp ~ Constant * exp(-0.01*Mw)
Migration = Constant * CPO * (Dp)1/2
Migration is significantly
Reduced when MW of
Additive is above ~1,200

26. So…The Unexpected Property…
LGP-11 does what is supposed to do. It “looks good”.
LGP-11 doesn’t do anything “bad” after melt processing. There are a lot of “bad” things that must be avoided.
LGP-11 is also “unique”. The unexpected property is that LGP-11 can be used to improve melt processing and reduce melt fracture.

27. Melt Fracture
Under certain conditions, blown film processing of LLDPE may result in melt fracture. This surface irregularity or roughness negatively affects the properties of the polymer. Melt fracture is dependent upon many variables including resin type, additive formulation, melt temperature, output rates, equipment design, etc.
Polymeric Process Aids (PPA) are commonly used to reduce or eliminate melt fracture
LLDPE (no PPA) LLDPE w/PPA
Source: Paul Neumann, Dyneon/3M, PLACE Conference, 2007

28. Melt Fracture - PPAs
Polymeric Process Aids (PPA) are generally composed of fluoropolymers, which are often combined with other additives such as interfacial agents, minerals or other polymers. They are used at levels from ~300ppm to 1000ppm.
PPAs have a high affinity for metal surfaces, and form a fluoropolymer layer on the extruder die, which allows the melt to easily slip through.
The use of PPAs improve melt processing. Benefits include increased throughput, lower operating pressures, reduced gel formation, ability to run equipment at lower temperatures or reduced film thickness, reduced die buildup, etc.

29. Melt Fracture - PPAs
As the PPA coats the extruder die over time, melt fracture is gradually decreased. The time it takes to fully remove melt fracture is called “Time To Clear”.
Source: Steve Oriani, DuPont, SPE Polyolefins Conference, 2010

30. Interfacial Agents - PPAs
Interfacial agents are commonly used with fluoropolymer PPAs, although they do not prevent melt fracture by themselves.
They improve the coating process of the PPA and increase their general effectiveness. They are “synergistic” in that a blend of a an interfacial agent and a fluoropolymer is often more effective than the fluoropolymer by itself.
Interfacial agents are often low molecular weight polar polymers such as Polyethylene Glycol (PEG) and Polycaprolactone (PCL)

31. Melt Fracture Effects
Various factors influence the onset of melt fracture such as temperature, throughput rates, resin type, die geometry and additive interactions.
Interfacial additives improve PPA performance
Other additives can negatively affect PPA performance

32. Negative Interactions
Various additives negatively interact with PPAs
Antiblocks such as amorphous silica and talc
Fillers such as calcium carbonate
Hydrotalcites
Highly basic HALS UV stabilizers
Carbon black
TiO2

33. Phosphites and Melt Fracture
Most commonly used Phosphite stabilizers are either monophosphites or diphosphites.
Phosphite stabilizers could be considered “bystanders” when examining their structure-activity effects on melt fracture. Phosphites are generally not considered good nor bad when comparing different commercial products. However, if not used properly, degradation of the polymer can occur which negatively affects melt fracture.

34. Advantage of a Polymeric Phosphite
Unlike commodity phosphites, the polymeric nature and backbone structure of LGP-11 lends itself to beneficial properties that are similar to interfacial polymeric agents.
LGP-11 itself does not act as a PPA, but rather improves melt fracture performance when used in conjunction with a PPA
The replacement of TNPP or other phosphites with LGP-11 improves melt fracture, even without switching the level or type of PPA, or changing the PPA interfacial agent.

35. LGP-11 Melt Fracture and Processing Benefits
LGP11 can be used to replace TNPP and other solid phosphites. This has several potential melt fracture and processing benefits:
Reduced time to clear melt fracture (quicker start-up)
Potential to decrease the PPA level (cost savings)
Ability to run equipment at higher throughput rates (lbs/hour) without observing melt fracture
Ability to operate the extruder at lower temperatures without observing melt fracture (less degradation, lower energy cost)
Potential to replace PEG (polyethylene glycol) interfacial agent. PEG reduces melt stability because of degradation.

36. Improvements in Melt Fracture
Polymer evaluations were run on a counter-rotating twin screw Brabender extruder with a flex lip die attachment.
A film/tape of 20mil was produced. Variables studies include temperature, PPA levels and RPMs (throughput).

37. Improvements in Melt Fracture – Time to Clear
Extruder was operated at conditions that initially produced 100% melt fracture.
0.8MI ZN LLDPE
Melt Temperature = 230°C
Shear Rate = 320 s-1
300ppm Primary AO
650ppm PPA (Fluoropolymer only, no PEG or other interfacial agents)
Via Direct Compounding
Phosphites were compared
1800ppm LGP-11
1800ppm TNPP

38. Improvements in Time to Clear Melt Fracture (Optical Microscope Picture of Film Surface)
TNPP (Initial) (30 Minutes) (60 Minutes)
LGP11 (Initial) (30 Minutes) (60 Minutes)
Flow Path

39. Time To Clear Melt Fracture
Reduction of PPA Level
TNPP did not completely clear melt fracture under these lab conditions. LGP11 cleared within 60 minutes.
The level of PPA was reduced from 650ppm to 350ppm and the Time to Clear melt fracture was measured.
LGP-11 clears melt fracture significantly quicker than TNPP (time saving) and also allows a reduction in PPA level and potential cost savings
Phosphite
PPA Level
Time To Clear Melt Fracture
TNPP
650
Did not clear melt fracture
LGP-11
Within 60 Minutes
350

40. Increased Extruder Output Rate
After the melt fracture was cleared (at 60 minutes) the output rate of the extruder was increased to determine the onset of melt fracture with respect to shear rate.
LGP-11 allows increased output without melt fracture under these lab conditions. A simple change from TNPP to LGP11 as the stabilizer could potentially increase equipment capacity, if melt fracture at the extruder-die is the limiting rate factor (not including bubble cooling and other variables)
Phosphite
PPA Level
Shear Rate*
Melt Fracture
(after 60min)
Output Rate
TNPP
650
237 s-1
100% Melt Fracture
4.6lbs/hour
LGP-11
No Melt Fracture
362 s-1
7.1lbs/hour
419 s-1
No Melt
Fracture
8.2lbs/hour
473 s-1
Slight Melt Fracture
9.3lbs/hour
TNPP resulted in melt fracture at 4.6lbs/hour
LGP11 showed no melt fracture at 8.2 lbs/hour, >75% increase in output rate compared to TNPP

41. Reduced Extrusion Temperature
Extruder was operated at conditions that initially produced 100% melt fracture.
0.8MI ZN LLDPE
300ppm Primary AO
600ppm PPA (Fluoroelastomer/PEG blend)
Via letdown of PPA masterbatch
Phosphites were compared
1800ppm LGP-11
1800ppm TNPP
Melt Temperatures compared at 230°C and 210°C
Lower processing temperatures
less thermal degradation/gels, lower energy consumption, potential improved cooling

42. Temperature Reduction
At time = 0, all formulations had 100% melt fracture
TNPP (After °C, Shear Rate = 473s-1)
Partial Melt Fracture
LGP-11 (After °C, Shear Rate = 473s-1)
No Melt Fracture
* Corrected Shear Rates

43. Temperature Reduction
Melt Temperature reduced from 230° to 210°C
TNPP (After °C, Shear Rate = 473s-1)
Partial Melt Fracture
LGP-11 (After °C, Shear Rate = 473s-1)
No Melt Fracture
* Corrected Shear Rates

44. Reduced Temperatures AND Increased Output Rates
Shear Rate Increased after 60 Minute Conditioning at 210°C
LGP-11 (After °C, Shear Rate = 473s-1)
No Melt Fracture
LGP-11 (After °C, Shear Rate = 642s-1)
No Melt Fracture

45. Theory : LGP-11 Acts as an Interfacial Agent
One explanation of improved properties: LGP-11 acts as an interfacial agent, due to its polymeric nature.
If so…LGP-11 should show improved melt fracture without the interfacial agent present.
Goal: compare melt fracture performance of SP-1 vs LGP-11 using PPAs with and without an interfacial agent
PPA1 (fluoroelastomer/PEG blend, PEG is the interfacial agent)
PPA2 (only fluoroelastomer, no PEG or other interfacial agent)

46. Theory : LGP11 Acts as an Interfacial Agent
Most of the commonly used PPAs contain either PEG or PCL along with the fluoroelastomer
The blend is synergistic, usually offering better performance than the fluoroelastomer by itself
Example PPA1:
25-35% Fluoroelastomer
60-70% PEG
5% “others” such as calcium carbonate or talc
Example PPA2:
Only Fluoroelastomer
No PEG/PCL

47. Extrusion Conditions 1MI LLDPE Metallocene Resin
Brabender ¾” Single Screw Extruder (1:25 L/D)
Melt Temp 200°C, shear rate of ~440 s-1
Ribbon die (2” width, 20mil thickness) with pressure probe attachment
Phosphites compared
1500ppm LGP-11
1500ppm SP-1
Both formulations contained 500ppm of a primary antioxidant

48. PPA With and Without Interfacial Agent
PPA formulation levels
PPA 1 used at 600ppm, equivalent to:
~ 180ppm Fluoroelastomer
~ 400ppm PEG
PPA 2 used at 180ppm
180ppm Fluoroelastomer
No PEG
Thus, the formulations contain ~ the same level of fluoroelastomer, the only difference is one contains PEG, the other does not.

49. PPA1 - Time To Clear Melt Fracture
LGP-11 with 600ppm PPA1 (Fluoroelastomer + PEG)
SP-1 with 600ppm PPA1 (Fluoroelastomer + PEG)
Both formulations adequately cleared melt fracture under these conditions using PPA1. LGP-11 cleared melt fracture quicker than SP-1.
LGP-11 formulation: cleared melt fracture in ~ 15 minutes
SP-1 formulation: cleared melt facture in ~ 30 minutes

50. PPA2 - Time To Clear Melt Fracture
LGP-11 with 180ppm PPA2 (Only Fluoroelastomer, No PEG)
SP-1 with 180ppm PPA2 (Only Fluoroelastomer, No PEG)
LGP11 formulation: cleared melt fracture in ~ 20 minutes
SP-1 formulation: did NOT completely clear melt fracture after 60 minutes

51. LGP-11
SP-1
10min min min
10min min min min

52. LGP-11 Pressure Reduction

53. LGP11 : Interfacial Agent/Synergist
SP-1 and LGP-11 cleared melt fracture with PPA1
SP-1 did not clear melt fracture with PPA2 (no PEG)
SP-1 “needed” the PEG interfacial agent
LGP-11 cleared melt fracture with or without PEG
LGP-11 did not “need” the PEG interfacial agent
LGP-11 resulted in lower pressure throughout the extrusion
Conclusion: It is likely that LGP-11, a polymeric phosphite, is acting similar to an interfacial agent

54. Dynamic Aspect – Thick Profile
Die Gap inches, Width – 1 inch
Extruder equilibrated for 30 minutes with SP-1/PPA2 formulated resin
At 30 minutes, the feed was switched to LGP-11/PPA2 formulated resin

55. Conclusions
LGP-11 provides good MI performance and excellent color performance versus other phosphites. The “easy” part.
LGP-11 doesn’t do anything “bad” after melt processing. It offers improved ancillary properties versus other phosphites such as improved compatibility, NOx-Gas Fade, low migration, etc.
The “unexpected” property is that LGP-11 is effective at reducing melt fracture, reducing pressure and improved overall processing.
Now, what next?
Story to be continued…

56. Thank You!